SOLUTIONS MANUAL FOR Anatomy & Physiology An Integrative Approach 1st Edition. Michael McKinley Vale by digitaldownload87

Anatomy & Physiology An Integrative Approach 1e Michael McKinley Valerie O'Loughlin Theresa Bidle (Solutions Manual (Answer Key) All Chapters, 100% Original Verified, A+ Grade) All Chapters Solutions Manual Supplement files download link at the end of this file. Answer Key Chapter 1 Answers to “What Did You Learn?” 1. Comparative anatomy 2. Anatomy is the study of structure and form. Physiology is the study of how the structures function. 3. Cardiovascular 4. An anatomist will describe various tissues within the esophagus and their arrangement relative to each other. The physiologist will focus on how the tissues are involved in, and possibly interact, during the process of swallowing. 5. The ability of organisms to respond to stimuli such as changes in either their external or internal environment provides them with a mechanism for maintaining a constant internal environment, even as the environment around them changes. 6. A higher level of organization does contain all of the levels beneath it. Each level of organization is a function of the arrangement of its subsequent subunits, which are in turn a function of the organization of their subunits. Therefore, each level organization is dependent on the organization of all of the levels below. 7. The urinary system is responsible for filtering and removing waste products from the blood. 8. A transverse plane, also called a horizontal or cross-sectional plane, would divide the mouth into superior and inferior sections. 9. Proximal 10. The term antebrachial refers to the forearm, the portion of the upper limb between the elbow and wrist. 11. The lungs are located within the thoracic cavity. The serous membranes surrounding them consist of a parietal pleura lining the inside of the body wall and a visceral pleura lining the individual lungs. 12. Epigastric 13. A homeostatic system consists of a receptor such as a sensory neuron in the skin or a stretch receptor within a muscle that detects either an internal or external stimulus; a control system that integrates the input from the receptor such as the brain or an endocrine gland; and an effector such as a muscle or a gland that causes changes in response to the stimulus. 14. The body may respond to a drop in temperature by decreasing the diameter of blood vessels carrying blood to the surface of the skin, thereby decreasing the amount of heat lost to external environment. Another response involves stimulation of skeletal muscles, causing “shivering” and thereby generating heat internally. 15. Negative feedback systems involve responses that are in opposition to the stimulus, thereby maintaining the environment near the set point or normal level. Conversely, positive feedback systems entail a series of responses each increasing in intensity until a climax event is reached, at which point the system will return to homeostasis. 16. Diabetes, an inability of the body to maintain blood sugar levels, may result in damage to anatomical structures throughout the body due to high levels of glucose.

Answers to “Do You Know the Basics?” 1. B Feedback: Surface anatomy correlates superficial markings on the surface of the body and skin to deeper anatomical features. 2. C Feedback: Organs are often composed of several tissue types working in concert to perform a common function. 3. A Feedback: An organism’s metabolism is the sum of all of its biochemical reactions.

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4. C Feedback: A midsagittal or median plane separates the body into equal right and left halves as compared to simply a sagittal section, which separates the body into unequal right and left portions. There can be numerous sagittal planes but only one possible midsagittal section along the midline of the body. 5. D Feedback: The term proximal is used to describe the position of a structure on an appendage closest to the point of attachment to the trunk. Although in standard anatomical position a structure that is proximal is often also superior, proximal is the correct term for describing the position along an appendage. The term superior may be used to describe positions along the axis of the body, closer to the head. 6. A Feedback: The patellar region is the anterior portion of the knee. The popliteal region is the posterior portion of the knee. 7. A Feedback: The diaphragm comprises the barrier between the superior thoracic cavity and the inferior abdominal cavity. The pelvic cavity is located inferior to the superior edges of the pelvic bones. 8. D Feedback: The pleural cavity surrounding the lungs consists of a parietal pleura lining the internal walls of the thoracic cavity and a visceral pleura lining the surface of the lungs. 9. B Feedback: Homeostasis is an automated process for maintaining a constant internal environment. 10. D Feedback: The effector increasing the stimulus is an example of positive feedback. In a negative feedback system, the response moves the system in opposition to the stimulus, back toward the set point.

11. Anatomy is the study of structure and form, whereas physiology is the study of how the structures function. It is important to understand the anatomy of a structure in order to understand how it performs its function. Conversely, understanding the function of an anatomical feature helps to put into perspective the significance of its arrangement. 12. The simplest level of organization within an organism is found at the chemical level and is composed of atoms and molecules. At the cellular level of organization, molecules are organized into cells and subcellular components, forming the basic units of life. Groupings of similar cells performing similar functions are referred to as tissues, and groups of tissues may be found working in concert, forming organs at the organ level of organization. Related groups of organs working together in order to coordinate activities within the organism are called organ systems. 13. A hierarchical organization, metabolism, growth and development, responsiveness, regulation, and reproduction are characteristics common to all living organisms. All living things are arranged in a hierarchical manner with increasing levels of complexity from molecules to cells. They are capable of metabolism, growth and development, and responsiveness to stimuli. They are also able to regulate their internal environment in order to maintain homeostasis, ultimately surviving long enough to reproduce. 14. The human body consists of eleven organ systems. They are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, urinary, digestive, and reproductive systems. 15. A body in anatomical position is standing upright with the feet flat on the floor. The upper limbs are at the side of the body with palms facing anteriorly. The head is level and the eyes are looking forward. 16. The forearm is the antebrachial region, the wrist is the carpal region, the chest is the thoracic region, the armpit is the axillary region, the thigh is the femoral region, and the entire foot is the pes. 17. The cranial cavity and vertebral canal are located within the posterior aspect of the body. The cranial cavity houses the brain and the vertebral canal contains the spinal cord.

18. The serous membranes are found lining the compartments of the ventral cavity of the body. They consist of a parietal layer lining the inside of the body wall and a visceral layer covering internal organs. In between the two membranes is a potential space, the serous cavity, which contains serous fluid. 19. A homeostatic system consists of a receptor that detects an internal or external stimulus, a control system that integrates the input from the receptor, and an effector such as a muscle or a gland that causes changes in response to the stimulus. 20. Negative feedback systems involve responses that are in opposition to the stimulus, thereby maintaining the environment near the set point or normal level. Conversely, positive feedback systems entail a series of responses, each increasing in intensity until a climax event is reached, at which point the system will return to homeostasis.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: The pain is coming from a region below the umbilicus, hence it is in the lower portion of the abdomen and it is located on the right side. It is therefore in the right lower quadrant. 2. D Feedback: The right iliac region is located just medial to the pelvic bones. 3. B Feedback: X-rays are not absorbed by soft tissue such as the appendix. They are usually used to visualize dense structures. 4. B Feedback: Sweat glands release heat at the surface of the skin. 5. B Feedback: Serotonin is a neurotransmitter responsible for regulating both pathways associated with depression in the brain and gastric motility in the stomach. Drugs such as SSRIs are used to treat depression in individuals with low levels of serotonin in the brain by inhibiting its reuptake by neurons. Because the SSRI drugs cannot specifically target the brain, they also have an effect within the digestive system, causing nausea and diarrhea.

Answers to “Can You Synthesize What You’ve Learned?” 1. Lynn has broken the bones within her forearm, the radius and ulna. She has an abrasion on her chin as well as bruising on her buttocks and thigh. 2. The epinephrine counteracted the effect of the bee sting, acting in opposition to the stimulus; it was therefore an example of negative feedback. 3. X-rays and CT scans are optimal for visualizing dense tissues such as tumors. An MRI or ultrasound would be better suited for examining soft tissues.

Chapter 2 Answers to “What Did You Learn?” 1. The mass of an atom is determined by the combined number of protons and neutrons within its nucleus. The charge is a function of the ratio of protons to electrons. 2. The nucleus of a chlorine atom consists of 17 protons and 17 neutrons. The electrons are arranged into three separate shells; the first shell closest to the nucleus contains two electrons, the second shell contains eight electrons, and the third outer shell contains seven electrons for a total of 17 electrons. 3. Isotopes are atoms of the same element that differ in their number of neutrons. In a radioisotope the extra neutrons will decay and be released as radiation. 4. Elements such as the noble gases have satisfied the octet rule by having a complete outer electron shell and are therefore not reactive. Other elements may form bonds in order to satisfy the octet rule and fill their outer shells. 5. Common cations of the human body include sodium ions (Na+), potassium ions (K+), calcium ions (Ca2+), magnesium ions (Mg2+), and hydrogen ions (H+). Common anions include chloride ions (Cl-), bicarbonate ions (HCO3-), and phosphate ions (PO43-). 6. Hydrogen (H), sodium (Na), magnesium (Mg), potassium (K), and chloride (Cl) 7. In order to satisfy the octet rule, atoms with only one electron in their outer shell may give up the electron, resulting in a slightly positive cation with a full outer shell. Conversely, atoms with seven electrons in their outer shell may accept an electron from another atom, becoming a slightly negative anion but with a full outer shell. 8. Ionic bonds are formed due to an attraction between ions with different charges; therefore, two positive cations cannot form an ionic bond with each other, nor can two negatively charged anions. 9. The molecular formula exhibits the type and number of atoms in a molecule; the structural formula also provides information on how the atoms are arranged. 10. Isomers are molecules composed of the same type and number of elements, but are arranged differently. 11. A covalent bond is formed when atoms share electrons in their outer orbitals in order to satisfy the octet rule. 12. Oxygen atoms each contain six electrons in their outer orbitals and each have room for two more. In a double bond they share two pairs of electrons and thereby each satisfies the octet rule. 13. A covalent bond between atoms of the same element will result in an equal distribution of electrons across the molecule since both atoms are equally electronegative, resulting in a nonpolar molecule. Molecules composed of different atoms result in an unequal distribution of charge across the molecule, where more electronegative atoms have a slightly negative charge and less electronegative atoms are slightly less negative. Since oxygen and hydrogen atoms are nearly equal in terms of electronegativity, atoms of these two different elements can also form nonpolar covalent bonds. 14. Both molecular oxygen (O2) and carbon dioxide (CO2) are nonpolar molecules. 15. A hydrogen bond is an intermolecular attraction between a slightly positive hydrogen atom and another slightly negative atom. 16. Hydrogen bonding is an important factor behind many of the properties of water molecules. 17. Surfactant is required to break cohesive attraction between water molecules in the alveoli of the lungs. The high heat of vaporization of water molecules makes them an effective mechanism for dissipating heat at the surface of the skin. 18. Nonelectrolytic molecules such as glucose do not dissociate in water. Electrolytes such as sodium chloride (NaCl) disassociate into constituent ions in an aqueous environment, forming a solution capable of conducting electricity. 19. In an aqueous environment, amphipathic molecules such as phospholipids will orient themselves so that their hydrophobic domains face each other while the hydrophilic domains are exposed to water. This is the basis behind the arrangement of phospholipids within a phospholipid bilayer.

20. Each water molecule can disassociate into one negatively charged hydroxyl ion and one positively charged hydrogen ion, leaving it with an equal distribution of positive and negative charges, which is considered neutral. 21. An acid is capable of releasing hydrogen ions in an aqueous environment. 22. pH is the relative measure of hydrogen ions in a solution. 23. Buffers maintain the pH of physiologic solutions within a normal range by absorbing hydrogen ions when an acid is added or hydroxyls when a base is added to the solution. 24. Blood is a suspension of formed elements that settle out of solution when a sample is left standing. 25. Blood is also considered a colloid because it contains numerous proteins and a solution because of its numerous dissolved solutes, such as ions and sugars. 26. The concentration of a solution may be expressed as either the mass of solute/volume of solution, percent of mass of solute in 100 milliliters of solution, moles of solute/liter of solution (molarity), or the moles of solute/kilogram of solvent (molality). 27. Biological molecules typically contain carbon (C), hydrogen (H), and oxygen (O) and in some cases may also contain nitrogen (N), phosphorus (P), and sulfur (S). Of these, hydrogen is the only one capable of forming a common biological ion. 28. Carboxylic acids and phosphates are capable of acting as acids. 29. A polymer is composed of repeating monomer subunits. Proteins are composed of amino acids, carbohydrates are composed of simple sugars, and nucleic acids are composed nucleotides. 30. Lipids are hydrophobic molecules and do not typically dissolve in water. 31. Phospholipids contain both a hydrophilic head group and a pair of hydrophobic fatty acid tails, making them ideally suited for forming cellular membranes. 32. Glycogen can be found within the liver and muscle tissue of animals and is composed of repeating glucose subunits. 33. Fructose, glucose, and galactose are monosaccharides. Sucrose, maltose, and galactose are disaccharides. Glycogen and starch are polysaccharides. 34. Nucleic acids store and transfer genetic information within cells. 35. RNA molecules contain a ribose sugar rather than the deoxyribose sugar of DNA. The nucleotide thymine is present in DNA. In its place, RNA contains the nucleotide uracil. 36. Amino acids are the monomers of a protein and are held together by peptide bonds. 37. A dipeptide consists of 2 amino acids, an oligopeptide contains 3 to 20 amino acids, a polypeptide contains 21 to 199 amino acids, and a protein consists of 200 or more amino acids. The term protein is generally used to refer to any of these molecules. 38. The R group of leucine is a short nonpolar hydrocarbon, making it a nonpolar amino acid. 39. The tertiary structure of a protein is its three-dimensional shape. The quaternary structure describes the interaction of two or more polypeptide chains within a functional protein. 40. Denaturing a protein changes its conformation and often affects its activity. Exposure of a protein to hydrogen ions can denature a protein by disrupting electrostatic interactions such as ionic bonds within the molecule.

Answers to “Do You Know the Basics?” 1. C Feedback: Isotopes are atoms of the same element that differ in the number of neutrons.

2. A Feedback: Lipids are hydrophobic molecules and are not soluble in water. 3. C Feedback: Water has a high specific heat, allowing it to absorb energy without changing temperature. Conversely, the high heat of vaporization for water allows it to dissipate a large amount of energy during evaporative cooling of the skin. 4. D Feedback: A pH less than 7.0 is acidic and a pH greater than 7.0 is basic. 5. D Feedback: The formed elements of blood act as a suspension. Dissolved proteins in the plasma act as a colloid. The numerous dissolved solutes also make it a solution. 6. A Feedback: Triglycerides are not considered polymers because they are not composed of repeating monomer subunits. 7. C Feedback: Glucose is stored in animal tissues as glycogen. 8. B Feedback: Although phosphates which contain phosphorus are common ions in the body, phosphorus itself is not a common ion. 9. B Feedback: A hydrogen bond is an intermolecular attraction between a slightly positive hydrogen atom and another slightly negative atom. 10. B Feedback: Denaturing a protein changes its conformation. Excessive denaturation can permanently affect protein structure and possibly its function as well. 11. Common cations of the human body include sodium ions (Na+), potassium ions (K+), calcium ions (Ca2+), magnesium ions (Mg2+), and hydrogen ions (H+). Common anions include chloride ions (Cl-), bicarbonate ions (HCO3-), and phosphate ions (PO43-). 12. A polar molecule such as water results from an unequal distribution of electrons between covalently bonded atoms. Oxygen, the more electronegative of the atoms, will have a stronger pull on the electrons and will thus have a slightly more negative charge around it. The hydrogen atom will be relatively more positive (or less negative). Two water molecules can form a hydrogen bond between their opposite poles, whereby relatively positive hydrogen will be attracted to relatively negative oxygen on the other molecule. 13.

14. Covalently bonded compounds such as glucose will not dissociate when dissolved in water; however, they will remain in solution after the mixture is no longer agitated. Ionic compounds such as sodium chloride (NaCl) will disassociate in water. The polar water molecules will disrupt the electrostatic interactions between sodium and chloride ions, thereby separating them. 15. An acid contributes hydrogen ions to a solution, making it more acidic; a base absorbs hydrogen ions from a solution, making it more basic. pH is the measure of hydrogen ions in a solution. A buffer is a solution capable of absorbing either hydrogen or hydroxyl ions, thereby maintaining its pH when acids or bases are added.

16. The concentration of a solution may be expressed as either the ratio of the mass of solute compared to the volume of the solution, as the percent of mass of solute in 100 milliliters of solution, as the number of moles of solute per liter of solution (molarity), or the number of moles of solute per kilogram of solvent (molality). 17. Proteins are composed of amino acids; carbohydrates are composed of simple sugars; nucleic acids are composed of nucleotides; and lipids consist of fatty acids. 18. The catabolism of either the nitrogenous bases present in nucleotides or the amine groups of amino acids may result in nitrogenous waste that must be removed from the body by the kidneys. 19. In an aqueous environment, amphipathic molecules such as phospholipids will orient themselves so that their hydrophobic domains face each other while the hydrophilic domains are exposed to water. This is the basis behind the arrangement of phospholipids within a phospholipid bilayer. 20. Denaturing a protein changes its conformation and often affects its activity. Exposure of a protein to a pH outside of its norm or an increase in temperature can denature a protein by disrupting electrostatic interactions such as ionic bonds within the molecule.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Surfactant is a detergent that prevents hydrostatic interactions between water molecules, thereby preventing the lungs from collapsing. Premature babies often lack the ability to produce surfactant and are at risk for respiratory problems. 2. B Feedback: Electrolytes such as sodium chloride (NaCl) dissociate into constituent ions in an aqueous environment, forming a solution capable of conducting electricity. Nonelectrolytic molecules such as glucose do not dissociate in water. 3. B Feedback: Isotopes are atoms of the same element that differ in their number of neutrons. In a radioisotope the extra neutrons will decay and be released as radiation, which may be measured or visualized during a diagnostic test. 4. D Feedback: Calcium ions are an important structural component of bone tissue. 5. C Feedback: Proteins consist of covalently bonded amino acids held together by peptide bond.

Answers to “Can You Synthesize What You’ve Learned?” 1. High-energy radiation can affect bonds within nucleotides, thereby damaging DNA. 2. Acidosis is an increase in the number of hydrogen ions in the blood, resulting in a lower pH. The increasing number of hydrogen ions may start to damage the hydrostatic interactions holding proteins together, destroying tertiary structure and denaturing the proteins. 3. The drug would regulate the levels of the monosaccharide glucose within the blood.

Chapter 3 Answers to “What Did You Learn?” 1. Kinetic energy represents a change in position. Movement of sodium ions along a concentration gradient or the movement of electrons from higher to lower energy state are both examples of kinetic energy. 2. The movement of muscle is an example of mechanical energy, a form of kinetic energy. 3. Even though energy can neither be created nor destroyed, it can change forms. Such transformations are rarely completely efficient, resulting in the release of some of the energy as heat, the least organized form of energy. 4. Reactants are the substrates prior to a reaction. The reactants are converted to products during the reaction. 5. This synthesis reaction would be anabolic, because it would result in a more complicated structure. It would also be endergonic, since it would require an input of energy. 6. ATP is produced by exergonic reactions. It is often used to couple exergonic reactions to endergonic reactions that require an input of energy. 7. When equilibrium is disturbed in a reversible reaction, the system will adjust driving the reaction toward either the reactants or the products, until equilibrium is reestablished. 8. Although raising the temperature of a reaction increases the kinetic energy of molecules, in a biological system this can decrease the rate of the reaction by denaturing the enzymes involved. 9. Enzymes lower the energy of activation required for a reaction. 10. The active site of an enzyme is the temporary binding site of the substrate on the enzyme. 11. Enzymes are proteins that catalyze metabolic reaction by lowering the activation energy necessary for the reaction. The structure of the protein directly affects its affinity for its specific substrate. Inorganic cofactors are often associated with enzymes facilitating their actions. Organic cofactors (coenzymes not attached to the protein) such as NAD+ and FAD+ may also be required to complete enzymatic reactions. 12. The name of an enzyme usually describes its action and usually contains the suffix -ase. 13. The rate of an enzyme-catalyzed reaction will increase as the concentration of substrate is increased, until all of the enzyme molecules are saturated. Decreasing temperature from an enzyme’s optimum range will gradually decrease activity by decreasing the kinetic energy of the system. Increasing temperature will have a more sudden negative effect on enzyme function as the molecule is denatured. Changing pH of an enzymatic reaction will readily denature the protein as the excessive hydrogen or hydroxyl ions interfere with electrostatic interactions within the enzyme, denaturing it. 14. Competitive inhibitors affect enzyme activity by competing with substrates at the active site. Noncompetitive inhibitors modulate the shape of the enzyme by binding to an allosteric binding site, outside of the active site, thereby affecting the overall shape of the enzyme and its function. 15. A metabolic pathway consists of a series of enzyme-catalyzed reactions. Often the final product of the pathway serves as an allosteric inhibitor of enzymes within the pathway, providing for negative feedback within the system. 16. Phosphorylation and dephosphorylation entail the addition or removal of phosphates, respectively. Addition of a phosphate to an enzyme affects the shape, and therefore the function, of the enzyme. 17. C6H12O2 + 6 O2 → 6 CO2 + 6 H2O. The catabolism of glucose, an exergonic reaction, results in the production of six molecules of carbon dioxide. Oxygen acts as the final electron acceptor in the process which involves the energy from the release of CO2 to synthesize ATP. 18. Cellular oxidation begins with glycolysis in the cytosol of the cell. The remaining steps are the intermediate reactions, the citric acid cycle, and the electron transport chain which occur within the mitochondria.

19. Glycolysis is an anaerobic process that occurs in the cytosol of a cell. The net reaction entails the synthesis of two 3-carbon pyruvate molecules from one 6-carbon molecule of glucose. The reaction involves the initial input of two molecules of ATP and yields four, for a net yield of two molecules of ATP. Two molecules of NAD+ are also reduced to form NADH + H+ from electrons and protons released during the oxidation of glucose. 20. Under aerobic conditions, in the presence of oxygen, pyruvate enters the mitochondria to complete oxidation. Under anaerobic conditions pyruvate will be converted to lactate. 21. The intermediate stage of cellular respiration is an aerobic process that links glycolysis with the citric acid cycle. It is catalyzed by pyruvate dehydrogenase and involves the decarboxylation of pyruvate to yield carbon dioxide. The remainder of the molecule is combined with coenzyme A to form the acetyl CoA complex. Two molecules of NAD+ are reduced to form NADH + H+ from electrons and protons released during the oxidation of pyruvate to acetyl CoA. 22. The citric acid cycle is an aerobic process that occurs within the matrix of mitochondria. Assuming one molecule of glucose, the process entails the catabolism of one acetyl CoA molecule, yielding one oxaloacetate and two molecules of carbon dioxide. The oxidation of acetyl CoA also yields three molecules of NADH + H+, one molecule of FADH2, and one molecule of ATP. 23. Cellular respiration of one molecule of glucose yields two molecules of ATP and two molecules of NAHD during glycolysis, and two molecules of NADH during the intermediate stage. The citric acid cycle yields six more molecules of NADH + H+, two molecules of FADH2, and two more molecules of ATP. 24. NADH and FADH2 couple the oxidation of glucose and subsequently pyruvate to the electron transport chain. 25. Oxidative phosphorylation entails the transfer of electrons from NADH and FADH2 to the electron transport chain, the establishment of a proton gradient through the use of energy from electron passed along the chain, and finally the diffusion of the proton gradient through the ATP synthetase to form bonds between ADP and Pi. 26. Glycolysis yields two molecules of ATP for every one molecule of glucose. Under aerobic conditions the complete oxidation of one molecule of glucose yields 36 molecules of ATP. 27. Under anaerobic conditions pyruvate is converted to lactate in the cytosol. This facilitates the regeneration of two molecules of NAD+ which can then be utilized to continue with the glycolysis of more glucose, yielding ATP. 28. The beta-oxidation of fatty acids converts them to acetyl CoA, which can only be consumed during the aerobic stage of cellular respiration.

Answers to “Do You Know the Basics?” 1. A Feedback: Energy from the hydrolysis of ATP (a chemical reaction) is used to power the sliding of filaments during a muscle contraction (a mechanical process). 2. A Feedback: Oxidation-reduction reactions involve the exchange of electrons between the oxidizing and the reducing agent. 3. B Feedback: Increasing pH interferes with electrostatic interactions within the enzyme, causing denaturation of the molecule. 4. C Feedback: Since ATP does not bind to the active site of phosphofructokinase, it is not a competitive inhibitor. It is an example of an allosteric/noncompetitive inhibitor. 5. D Feedback: Enzymes are very specific for their substrate and are therefore only involved in very particular reactions. 6. A Feedback: Glycolysis yields two molecules of pyruvate from one molecule of glucose.

7. D Feedback: NAD+ and FAD+ are coenzymes involved in oxidation-reduction reactions where they shuttle electrons away from the substrate. 8. A Feedback: Glycolysis is able to continue under anaerobic conditions, yielding two molecules of ATP, two molecules of NADH, and one molecule of lactate. 9. C Feedback: One molecule of glucose may yield 2 molecules of ATP under anaerobic conditions and 36 molecules of ATP if oxygen is present. 10. D Feedback: Oxidative phosphorylation entails the transfer of electrons from NADH and FADH2 to the electron transport chain, the establishment of a proton gradient through the use of energy from electrons passed along the chain, and finally the diffusion of the proton gradient through the ATP synthase to form bonds between ADP and Pi. 11. Energy stored in glycogen or triglycerides represents chemical energy, a form of potential energy. Electrical energy such as the propagation of an impulse along a neuron, the mechanical energy of a muscle contraction, or sound energy vibrating either the tympanic membrane in the ear or the vocal folds of the larynx are all examples of kinetic energy. 12. Chemical reactions are classified as either reactions that cause a structural change to a molecule, reactions that change the chemical energy of a molecule, or reactions that are either reversible or irreversible. An oxidation-reduction reaction is an exchange reaction and would therefore be an example of a change in chemical structure. 13. ATP is oxidized to ADP and Pi, releasing energy which is used to do work in the cell. The regeneration ATP from ADP and Pi is then coupled to the oxidation of hydrocarbons during cellular respiration. 14. Enzymes are globular proteins that catalyze metabolic reaction by lowering the activation energy necessary for the reaction. The structure of the protein directly affects its affinity for its specific substrate. Thus the slightest conformational change due to a change in temperature or pH can readily affect enzyme function. 15. A metabolic pathway consists of a series of enzyme-catalyzed reactions. Often the final product of the pathway serves as an allosteric inhibitor of enzymes within the pathway, causing a conformation change in the protein. This rearrangement may affect the affinity for the substrate at the enzymes' active site, thereby providing for negative feedback within the system. 16. Glycolysis is an anaerobic process that occurs in the cytosol of a cell. The net reaction entails the synthesis of two 3-carbon pyruvate molecules from one 6-carbon molecule of glucose. The reaction involves the initial input of two molecules of ATP and yields four, for a net yield of two molecules of ATP. Two molecules of NAD+ are also reduced to form NADH + H+ from electrons and protons released during the oxidation of glucose. 17. Under aerobic conditions, in the presence of oxygen, pyruvate enters the mitochondria to complete oxidation. Under anaerobic conditions pyruvate will be converted to lactate. 18. Oxygen serves as the final electron acceptor of the electron transport chain during oxidative phosphorylation. Molecular oxygen (O2) in the mitochondrial matrix is split and each oxygen atom along with electrons from the electron transport chain combine with two hydrogen ions, yielding a molecule of water. 19. The carbon in carbon dioxide is liberated from the hydrocarbon backbone of sugars or other organic molecules used to fuel cellular respiration. 20. Healthy respiratory and cardiovascular systems provide metabolically active tissues with adequate oxygen to drive efficient aerobic respiration. Tissues deprived of oxygen will not be able to burn fuels efficiently nor produce adequate amounts of ATP.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: The enzyme tyrosinase is required to convert tyrosine to melanin.

2. D Feedback: Decreased respiratory function will lead to a deficiency in oxygen and thus anaerobic respiration, not aerobic respiration. 3. B Feedback: The reversible reaction will be driven toward the synthesis of carbonic acid (H2CO3), which will spontaneously decompose to hydrogen (H+) and bicarbonate ions (HCO3). The result will be a decrease in the pH of the blood, a condition known as respiratory acidosis. 4. D Feedback: Individuals with anemia, asthma, or heart failure would have a diminished capacity for delivering oxygen to tissues. An athlete would have optimized capacity for oxygen transport and therefore normal ATP production. 5. C Feedback: By uncoupling the proton gradient within the intermembrane space of mitochondria from the synthesis of ATP, the majority of energy from foods would be lost as heat rather than stored as chemical energy.

Answers to “Can You Synthesize What You’ve Learned?” 1. An asthma attack would decrease Tiffany’s ability to ventilate her lungs with air. The result would be a decrease in the amount of oxygen reaching her tissues and less energy production because of a decrease in aerobic respiration. 2. A patient’s aerobic fitness corresponds directly to the patient's ability for ATP production. Increased fitness provides for more efficient delivery of oxygen to tissues, allowing for effective aerobic respiration of fuels. 3. If inhibition of a metabolic pathway does not occur, the product will accumulate. This will drive the reaction in the opposite direction, unless the product is removed or metabolized as part of another pathway.

Chapter 4 Answers to “What Did You Learn?” 1. Electron microscopy utilizes electrons rather than photons of light to visualize the specimen, providing greater resolution. 2. The typical cell ranges from 7 to 120 μm in diameter. 3. The plasma membrane is the outer (phospholipid bilayer) covering of the cell. The genetic material is located within the nucleus. Aside from the nucleus, everything else within the plasma membrane is in the cytoplasm. 4. The plasma membrane defines the boundary of the cell and maintains its integrity. 5. The plasma membrane consists of phospholipid molecules configured into a bilayer. The hydrophobic tails of each layer are oriented toward each other, while the hydrophilic (polar) heads are exposed to aqueous environments. Thus the cytosol is isolated from the extracellular (interstitial) fluid by the phospholipid bilayer. 6. Transport proteins are integral membrane proteins that function as carriers, channels, or pumps to facilitate movement through the plasma membrane. 7. O2 and CO2 do not require transporters. They may pass through the phospholipid bilayer by simple diffusion. 8. Small ions and polar molecules may be transported across the plasma membrane by facilitated diffusion. Small ions diffuse through pores or channels, whereas small polar molecules require carrier proteins. 9. Osmosis is the passive movement of water through a semipermeable membrane. 10. The tonicity of a cell placed into an isotonic solution will not change. A cell placed into a hypertonic solution will lose tonicity as more water moves out of the cell than back into the cell. The converse will occur when a cell is placed into a hypotonic solution— tonicity will increase as more water moves into the cell than is moving out. 11. The net movement of water will be toward the hypertonic solution. 12. Secondary active transport often couples the movement of one molecule down its concentration gradient to movement of another molecule against its gradient. 13. A white blood cell ingesting a microbe is an example of phagocytosis. 14. Interactions between the glycocalyxes of two cells may be seen during the recognition of cells by the immune system, during the interaction of eggs and sperm at the onset of fertilization, or during the contact inhibition of growth within tissues. 15. Enzyme receptors act as kinases directly in response to a stimulus; G protein–coupled receptors activate a downstream kinase through a second messenger. 16. Lysosomes and peroxisomes are involved in “digestion” within the cell. Lysosomes enzymatically degrade various substrates. Peroxisomes contain the mechanisms for oxidation of fatty acids. Mitochondria in the cell are responsible for the majority of ATP synthesis. 17. The plasma membrane forms vesicles during endocytosis. Vesicles formed by the endoplasmic reticulum and Golgi apparatus may be involved in exocytosis. 18. Proteasomes are non-membrane-bound organelles, responsible for the digestion of proteins. 19. Microvilli tend to be much shorter and more densely packed than cilia. Although both entail a fold within the plasma membrane of a cell organized by the cytoskeleton, cilia involve a mechanism for movement whereas microvilli usually serve to increase the surface area of the cell. 20. Although both desmosomes and tight junctions hold adjacent cells together, only tight junctions prevent the movement of substance in between the neighboring epithelial cells. 21. Nuclear pores permit the movement of ions in or out of the nucleus as well as the movement of RNA out of the nucleus.

22. The nucleolus is the site of ribosome formation in the nucleus. 23. Unwound DNA is referred to as chromatin. It will condense to chromosomes in preparation for mitosis (nuclear division). A gene is a sequence of DNA responsible for the production of a specific polypeptide chain. 24. Transcription involves the arrangement of ribonucleotides along a DNA template by an RNA polymerase. 25. A codon is a three nucleotide base sequence of RNA. Each codon codes for either an amino acid or the termination of translation. The anticodon is the tRNA complement to the codon, which permits the tRNA to serve as an adaptor between the codon and an amino acid. 26. As the mRNA feeds through the ribosome complex, translation begins when the first start codon (AUG) enters the P site. Within the P site the codon on the mRNA is paired with an anticodon on a tRNA molecule carrying the corresponding amino acid, at which time this first codon moves into the A site of the ribosome, bringing the next codon on the mRNA strand into the P site. This second codon is then paired with its corresponding tRNA molecule, which brings its corresponding amino acid, and a peptide bond forms between the two amino acids. At this point the first amino acid is released and the mRNA molecule shifts once again within the ribosome. The process continues until a stop codon enters the P site, signaling the termination of translation. 27. DNA is responsible for directing the synthesis of the proteins that carry out body functions. 28. Chromatin is a spread-out arrangement of DNA, well suited to facilitate transcription and DNA replication. Chromosomes are a highly organized and condensed form of DNA, better suited for nuclear division (mitosis). 29. DNA replication entails the unwinding of the DNA double helix and the breaking of hydrogen bonds in between the two complementary strands. A new strand of DNA is assembled off of each of the original template strands, which then each reform into two identical double helixes of DNA. 30. The final preparations for nuclear division occur during prophase as chromatin condenses into chromosomes, the nuclear envelope disappears, microtubules arrange into spindle fibers, and centrioles move to opposite poles within the cell. During metaphase the chromosomes align at the equatorial plane of the cell. If metaphase is successful the sister chromatids begin to separate during anaphase. Telophase is designated as the point at which the segregation of sister chromatids to opposite poles is complete, the nuclear envelope reforms around each daughter nucleus, and chromosomes unwind back to chromatin. Cytokinesis, splitting of the plasma membrane and cytoplasm, may start concurrently or immediately following telophase. 31. During apoptosis DNA is enzymatically cleaved into small fragments.

Answers to “Do You Know the Basics?” 1. C Feedback: Not all cells are capable of replication. All cells are capable of acquiring nutrients, maintaining a plasma membrane, and removing waste. 2. A Feedback: The plasma membrane is a phospholipid bilayer. Although other molecules such as cholesterol, sugars, and proteins may be present within the plasma membrane, phospholipid is the predominant structural component. 3. B Feedback: Facilitated diffusion through either a channel or a carrier protein requires a concentration gradient but does not require energy from ATP. 4. C Feedback: Since the movement of one substance down its concentration gradient is coupled to the movement of another molecule against its particular gradient, this is an example of secondary active transport. Because both molecules are moving in the same direction, the transport molecule would be a symporter. 5. A Feedback: Lysosomes, the Golgi apparatus, and the endoplasmic reticulum are all composed of phospholipid membranes. Ribosomes do not have a membrane.

6. A Feedback: The smooth endoplasmic reticulum is responsible for lipid synthesis and the detoxification of lipid-soluble molecules such as alcohol. 7. C Feedback: Proteasomes are responsible for degrading malformed, damaged, or obsolete proteins. 8. D Feedback: Transcription forms RNA from DNA. Translation forms a polypeptide chain from RNA. 9. A Feedback: Prophase involves all of the preparatory steps necessary prior to nuclear division such as condensation of chromatin to chromosomes, spindle fiber formation, disappearance of the nuclear envelope, and migration of centrioles to opposite poles. 10. B Feedback: DNA within the nucleus is required for protein synthesis and cell division. 11. The plasma membrane is the outer (phospholipid bilayer) covering of the cell. The genetic material is located within the nucleus. Aside from the nucleus, everything else within the plasma membrane is in the cytoplasm. 12. Proteins associated with the plasma membrane of a cell may function as either transport proteins regulating passage into or out of the cell; cell surface receptors that trigger downstream cellular events in response to binding of ligands; surface markers; enzymes catalyzing reactions; anchoring sites for the cytoskeleton; or as cell adhesion proteins that permit interactions with other cells. 13. During simple diffusion, small nonpolar molecules are able to diffuse through the phospholipid bilayer down their concentration gradient without the need of transport molecules. Facilitated diffusion entails polar molecules or charged ions traveling through the phospholipid bilayer down their concentration gradient, and requires pores or carrier molecules. The diffusion of water molecules by osmosis requires aquaporin channels and is also a passive process. 14. Primary active transport directly utilizes the energy from the hydrolysis of ATP to move solutes against their concentration gradients. Secondary active transport couples the movement of one molecule down its concentration gradient to the movement of another molecule against its gradient. Vesicular transport requires an input of energy to drive the bulk movement of molecules into or out of a cell through vesicles. 15. The endoplasmic reticulum consists of a series of folded membranes within the cytoplasm. The rough endoplasmic reticulum is studded with ribosomes and is involved in protein synthesis. The smooth endoplasmic reticulum is responsible for lipid synthesis and the detoxification of lipid-soluble toxins. The Golgi apparatus consists of a series of flattened membranes, responsible for the modification of proteins. Lysosomes and peroxisomes are small vesicles containing metabolic enzymes. Lysosomes are responsible for the digestion of cellular debris or ingested structures. Peroxisomes process free radicals and participate in the beta-oxidation of fatty acids. Unlike other membrane-bound organelles, mitochondria consist of two distinct membranes, one within the other. They are responsible for the majority of ATP synthesis within the cell. 16. Microfilaments consisting of intertwined actin filaments line the inner leaf of the plasma membrane and are involved in changes to its shape. Intermediate filaments vary in composition, depending on the cell type, and are involved in intercellular junctions. Lastly, microtubules are ephemeral structures, constantly reorganizing, responsible for movement and transportation within the cell. 17. Microvilli tend to be much shorter and more densely packed than cilia. Although both entail a fold within the plasma membrane of a cell organized by the cytoskeleton, cilia involve a mechanism for movement, whereas microvilli usually serve to increase the surface area of the cell. 18. Transcription is the process by which DNA is converted to mRNA during gene expression. The initiation of transcription is the key regulatory step in determining which genes will be expressed. Elongation involves the extension of the nascent strand by an RNA polymerase through complementary base pairing with the DNA template. Finally, the termination of transcription occurs as the polymerase reaches the terminal region of the gene and releases. Translation occurs within the cytoplasm either by free ribosomes or ribosomes associated with the endoplasmic reticulum. As the mRNA feeds through the ribosome complex, translation begins when the first start codon (AUG) enters the P site. Within the P site the codon on the mRNA is paired with an anticodon on a tRNA molecule carrying the corresponding amino acid, at which time this first codon moves into the A site of the ribosome, bringing the next codon on the mRNA strand into the P site. This second codon is then paired with its corresponding tRNA molecule, which brings its corresponding amino acid, and a peptide bond forms between

the two amino acids. At this point the first amino acid is released and the mRNA molecule shifts once again within the ribosome. The process continues until a stop codon enters the P site, signaling the termination of translation. 19. DNA is responsible for directing the synthesis of all of the proteins in the cell. By regulating gene expression, the presence of metabolic enzymes, receptors, or structural proteins may be affected. 20. During the first growth phase of the cell cycle, the cell carries out its specific metabolic activities and serves its function within the surrounding tissue. At the S phase the cell replicates DNA in preparation for cell division. The second growth phase entails gene expression in preparation for division. The mitosis phase consists of two, possibly overlapping, events. Mitosis is nuclear division whereas cytokinesis is the splitting of the cytoplasm and plasma membrane.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Lysosomes are responsible for digestion of organic molecules. 2. B Feedback: Receptor-mediated endocytosis is required to remove LDL from the blood. 3. C Feedback: Apoptosis removes defective cells before they can replicate and become a tumor. Many cancer cells have mutations affecting their ability to initiate apoptosis. 4. C Feedback: Testosterone is a hormone that requires a receptor to activate downstream events within the cell. 5. A Feedback: Protein synthesis is a two-step process: first transcription, then translation.

Answers to “Can You Synthesize What You’ve Learned?” 1. An inability to produce albumin would affect the osmolality of the blood, decreasing the osmotic pressure. 2. As the oxygen saturation of the blood decreases the concentration gradient will decrease, as will the net diffusion of oxygen out of the blood into tissues. 3. The removal of LDL from the blood into cells is accomplished by receptor-mediated endocytosis, the mechanism dependent upon the presence of receptor proteins. A mutation in the gene coding for the receptor(s) responsible for the endocytosis of LDL would result in an excess of cholesterol in the blood.

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Chapter 5 Answers to “What Did You Learn?” 1. Many epithelial tissues are exposed to damage and abrasion, and therefore need to be replaced frequently. 2. Epithelial cells line all of the membranes where substances may enter the body. They must therefore have the capacity to regulate what may pass through the membranes. 3. Simple epithelium consists of a single layer of cells. Stratified epithelium consists of two or more layers. 4. Simple squamous epithelium lines the air sacs of the lungs. 5. Keratinized stratified squamous epithelium is the correct tissue. 6. Multicellular exocrine glands consist of a duct and either a tubular or an acinar secretory section. 7. The cells of a merocrine gland secrete their products by exocytosis. The cells of a holocrine gland will rupture completely in order to release their contents. 8. Resident cells are fixed in position within the connective tissue. Wandering cells are components of the immune system and move through the tissue, providing for repair and for protection from infection. 9. Glycosaminoglycans (GAG) are large extracellular carbohydrates that absorb water within the ground substance of a connective tissue, thereby regulating the viscosity of the solution. 10. Connective tissues such as bone and cartilage support the entire body and act as sites for muscle attachments. Cartilage maintains the integrity and shape of structures such as the trachea and nasal septum. Outer layers of collagen surround and support nearly all of the organs in the body. 11. Mesenchyme is an embryonic tissue composed of stellate and spindle-shaped cells surrounded by a ground substance. It is the embryonic origin of all adult connective tissues. 12. Loose connective tissue consists predominantly of ground substance with few fibers. Dense connective tissues have very little ground substance, and consist largely of a dense arrangement of fibers. 13. Fibrocartilage may be well suited for resisting compression forces and/or bearing weight. It contains very little ground substance; it does however have numerous collagen fibers. It does not have a perichondrium. 14. Blood is derived from mesenchyme like all other connective tissues. It contains a very fluid ground substance called plasma, numerous dissolved proteins, and formed cellular elements. 15. Cardiac and skeletal muscles are both striated and contain similar arrangements of intracellular contractile proteins. Whereas cardiac muscle consists of individual branching cells, skeletal muscle consists of large multinucleated cells. Cardiac muscle is voluntary; skeletal muscle is involuntary. 16. Neurons are specialized for transmitting nervous impulses. Glial cells do not transmit the nervous impulse; however, they serve numerous critical support functions in the nervous system. 17. The stomach is an organ that contains all four tissue types. It is lined with epithelium, it has numerous layers of smooth muscle, it is highly innervated, and it contains several types of connective tissue. 18. The parietal layer lines the inside of the body wall. The deeper visceral layer lines organs. 19. The three primary germ layers—the ectoderm, endoderm, and mesoderm—form by the third week of embryonic development. 20. Hypertrophy is an increase in the size of cells within the tissue. Hyperplasia is an increase in the number of cells. 21. Epithelial tissues become thinner with age. The amount of collagen also decreases with age, affecting the pliability and resilience of connective tissues.

Answers to “Do You Know the Basics?” 1. D Feedback: Bone connective tissue is composed predominantly of mineralized calcium, which serves as the structural component of bones. 2. C Feedback: Areolar connective tissue is a loose connective tissue. It does not contain tightly packed fibers. 3. A Feedback: Mucous membranes line body cavities that are exposed to the outside of the body, such as in the respiratory, digestive, urinary, and reproductive systems. 4. A Feedback: Because simple squamous epithelium consists of only a single layer of epithelial cells, all of the cells are in direct contact with the basement membrane. 5. D Feedback: Epithelial tissue is avascular. It does not contain blood vessels. 6. C Feedback: All cartilage contains chondrocytes. Hyaline and elastic cartilages are surrounded by perichondrium. 7. C Feedback: Smooth muscle is derived from mesoderm. 8. B Feedback: Striated skeletal muscle cells fuse during embryonic development, and are therefore multinucleated. 9. B Feedback: The trachea is lined with pseudostratified ciliated columnar epithelium. 10. A Feedback: Merocrine glands secrete their products by exocytosis. 11. Epithelial tissues are composed primarily of cells without a lot of extracellular matrix. Because of their role in lining surfaces they posses polarity; they lack blood vessels; they are highly innervated; and they often have a high capacity for regeneration. Epithelial tissue is supported by a basement membrane, an underlying layer of connective tissue. 12. Epithelia are classified according to the number of layers in the tissue. Simple epithelium has only one layer. Stratified epithelium has two or more layers. Epithelium is also categorized based on the shape of cells: squamous, cuboidal, or columnar. 13. The lumen of the stomach is lined with simple columnar epithelium. The oral cavity is lined with stratified squamous epithelium. The urinary bladder is lined with transitional epithelium. The alveoli of the lungs are lined with simple squamous epithelium. 14. The cells of a merocrine gland secrete their products by exocytosis. Apocrine gland cells pinch off the entire apical domain of the plasma membrane. The entire cell of a halocrine gland ruptures in order to release its contents. 15. The skin is the cutaneous membrane. Mucous membranes line body cavities exposed to the outside of the body, whereas serous membranes line body cavities not exposed to the outside of the body. Synovial membranes produce synovial fluid within joints. 16. All connective tissues are derived from mesenchyme and have some proportion of ground substance, an extracellular matrix with various arrangements of large extracellular fibers. 17. Dense regular connective tissues have fibers arranged parallel to each other, whereas the fibers of dense irregular connective tissues are arranged in clumps that extend in various directions. 18. Hyaline cartilage is the most abundant type of cartilage, found at the ends of long bones, within rings of hyaline cartilage in the trachea, costal cartilage, and nasal septum. Elastic cartilage is located within the ear and epiglottis, where recoil and flexibility is

important. Fibrocartilage is optimized at resisting compression forces and is therefore found within intervertebral disks of the spinal column, menisci of the knees, and the pubic symphysis in between the two hip bones. 19. Skeletal muscle is voluntary; smooth and cardiac muscle are involuntary. Skeletal and cardiac muscle are striated, whereas smooth muscle is not. Skeletal muscle is primarily attached to bones, smooth muscle is present within the walls of hollow organs, and cardiac muscle is located only within the walls of the heart. 20. Neurons are specialized for transmitting nervous impulses. Glial cells do not transmit the nervous impulse; however, they serve numerous critical support functions in the nervous system.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Bursae contain synovial membranes. 2. C Feedback: The iris of the eye contains involuntary smooth muscle. 3. B Feedback: The mucous membrane within the cheek is lined with stratified squamous epithelium, which is well adapted for dealing with abrasion. 4. A Feedback: The mucous membrane within the cheek is lined with stratified squamous epithelium. 5. B Feedback: Although the deeper layers of stratified squamous epithelium are cuboidal, the tissue is named after the apical layers.

Answers to “Can You Synthesize What You’ve Learned?” 1. The student is looking at areolar connective tissue. 2. The articular cartilage at the ends of long bones consists of hyaline cartilage. Chondroitin sulfate is a component of the hyaline cartilage matrix. Therefore the supplement may help reduce the effects of arthritis in the joint, if that is indeed the cause of the pain.

Chapter 6 Answers to “What Did You Learn?” 1. The thorn would first penetrate the stratum corneum, the most superficial layer of the epidermis. It would then puncture the stratum lucidum, the stratum granulosum, the stratum spinosum, and finally the stratum basale. 2. Keratinization occurs due to the production of keratin, a hardening agent, within keratinocytes. Within the stratum spinosum, the cells fill up with keratin, and the nucleus and organelles become polymerized within the protein, eventually killing the cell. The cells then rupture, releasing keratin at the stratum granulosum. The subsequent superficial layers of the stratum lucidum and corneum consist of ruptured keratinocytes embedded in keratin. This provides for a hardened waterproof barrier between the external environment and the dermis below. 3. Hemoglobin turns red when bound to oxygen. As blood vessels bring hemoglobin close to the surface within the dermis, the skin takes on a reddish hue. 4. Friction ridges increase friction on contact with the skin. It has been hypothesized that they may also provide for pliability at the surface of the skin. 5. The papillary layer, composed primarily of areolar connective tissue, is the most superficial layer of the dermis. The reticular layer lies deep to the papillary layer, makes up the majority of the thickness of the skin, and is predominantly dense irregular connective tissue. Dermal papillae, the folds within the papillary layer, contain numerous capillaries and tactile receptors. The reticular layer contains most of the structures associated with the dermis, such as the hair follicles, sebaceous and sweat glands, nerves, and blood vessels. 6. Tension lines correspond to the direction of collagen bundles within the dermis of the skin. They are relevant clinically as these represent the optimum direction for an incision through the skin. An incision perpendicular to the tension lines can be easily pulled apart and is more likely to result in scarring. 7. On a cold day, vasoconstriction of dermal blood vessels shunts blood away from the surface of the skin in an effort to retain heat. Deprived of blood supply, the surface of the skin may appear pale. 8. The subcutaneous layer, deep to the skin, consists predominantly of areolar and adipose tissues. 9. The hyponychium is a thick layer of stratum corneum, deep to the free edge of the nail. The eponychium, or cuticle, is a small fold of skin that covers the proximal edge of the body of the nail. 10. The hair bulb, located within either the dermis or hypodermis of the skin, is the deepest and only living portion of the hair. Extending from the bulb toward the surface of the skin is the hair root. The hair shaft then extends beyond the surface of the skin. Neither the root nor the shaft contains living cells. 11. Hair on the scalp protects from exposure to the sun. Hairs within the nostrils, ears, or eyelashes protect the respective openings from debris. The eyebrows help to keep sweat out of the eyes. On a cold day the hair on the scalp also acts as insulation, preventing the loss of body heat. 12. Merocrine sweat glands are distributed throughout the body, whereas apocrine glands are primarily associated with hair follicles in the axillary, genital, and anal regions. Sweat produced by merocrine glands contains over 99% water with salts and trace amounts of metabolic waste. Its primary function is thermoregulation by evaporative cooling. Sweat from apocrine glands, along with water and salts, also contains an abundance of proteins and lipids. 13. Sebaceous glands secret an oily substance called sebum into the hair follicles and onto the hair shaft. 14. Keratinocytes produce vitamin D3, a precursor to vitamin D, when exposed to UV light. Further modification within first the liver and then the kidneys yields the active form of vitamin D. 15. The skin is, for the most part, waterproof. Most fluids leaving the body through the skin must be secreted by sweat glands. A very small amount of fluid may, however, be lost through transpiration—water moving through the epidermis but not through sweat glands. 16. Lipid-soluble molecules can pass through the epidermis. Therefore, lipid-soluble drugs, or water-soluble drugs surrounded by lipid-soluble carrier molecules, can be administered by application directly to the surface of the skin.

17. Vasodilation of arteries within the dermis allows more blood to reach the capillary beds within the papillary layer, facilitating the release of heat. Evaporative cooling of sweat also brings heat from deep inside the body to the surface of the skin. 18. Granular tissue occurs as the wound is actively rebuilding blood supply to the damaged region, prior to formation of new collagen or epithelium. It consists of developing capillaries and fibrocytes. 19. The epidermis is derived from ectoderm, whereas the dermis develops from the deeper mesoderm. 20. Chronic overexposure to UV light can damage the DNA of epidermal stem cells, inhibiting their ability to repair the skin.

Answers to “Do You Know the Basics?” 1. B Feedback: Sebaceous glands are holocrine glands. 2. D Feedback: Within the stratum granulosum of the epidermis, keratinocytes accumulate keratin inside their cytoplasm and eventually die, resulting in keratinization of the skin. 3. B Feedback: Sweat produced from merocrine glands consists primarily of water. In contrast, apocrine gland secretions also contain lipids and proteins, and sebaceous glands produce an oily substance called sebum. 4. B Feedback: Calcium is not stored within the dermis. However, the skin does act as a barrier separating the body from the external environment; it does participate in thermoregulation; and it does contain components of the immune system. 5. A Feedback: Dermal papillae are located within the papillary layer of the dermis and consist primarily of areolar connective tissue with numerous capillaries and tactile receptors. 6. B Feedback: Melanin is produced by melanocytes; it is then deposited into keratinocytes, where it accumulates within the stratum spinosum. 7. B Feedback: Similar to a first-degree burn, a second-degree burn involves the epidermis. However, a second-degree burn also includes damage to part of the dermis. A third-degree burn would include damage through all of the layers of the epidermis and dermis, as well as the deeper subcutaneous layer. 8. B Feedback: Cell division occurs within the matrix of the bulb. These cells are then pushed up, forming the medulla and cortex of the hair. 9. C Feedback: Tactile cell receptors within the dermal papillae detect touch sensations. 10. D Feedback: Granular tissue occurs as the wound is actively rebuilding blood supply to the damaged region, following the formation of a blood clot, but prior to the formation of new collagen or epithelium. 11. The stratum basale, spinosum, and granulosum contain living cells. The stratum lucidum (if present) and stratum corneum are composed of dead keratinocytes. 12. The stratum basale contains adult stem cells responsible for regenerating the tissue, tactile cells called Merkel cells, and melanocytes responsible for production of melanin, a UV absorbing pigment. The stratum spinosum mostly contains keratinocytes which are actively producing keratin, along with a few Langerhan’s cells which fight infection in the epidermis. The stratum corneum contains keratinocytes, impacted with keratin. Finally, the most superficial layers, the stratum lucidum (present only in thick skin) and corneum, contain dead keratinocytes imbedded within keratin.

13. The papillary layer, composed primarily of areolar connective tissue, is the most superficial layer of the dermis. The reticular layer lies deep to the papillary layer, makes up the majority of the thickness of the skin, and is predominantly dense irregular connective tissue. Dermal papillae, the folds within the papillary layer, contain numerous capillaries and tactile receptors. The reticular layer contains most of the structures associated with the dermis, such as the hair follicles, sebaceous and sweat glands, nerves, and blood vessels. 14. The nail body represents the majority of the nail structure, and is composed of highly keratinized epithelium. The living portion of the epidermis, deep to the nail body, is the nail bed. The eponychium, or cuticle, is a small fold of skin that covers the proximal edge of the nail body. The lunula is a whitish portion of the nail body, produced by a thick stratum basale within the underlying epidermis. 15. Lanugo is a fine unpigmented hair produced during the last trimester of fetal development. Vellus hair is the primary hair on humans and is found distributed through the body. Terminal hair is coarser than vellus hair and is located on the scalp, eyebrows, and eyelashes. After puberty it is also present in the axillary and pubic regions. 16. Ceruminous glands are located within the external acoustic meatus, where they secret the waterproof wax that lines the canal. 17. Keratinocytes produce vitamin D3, a precursor to vitamin D, when exposed to UV light. Further modification within first the liver and then the kidneys yields the active form of vitamin D. 18. The initial stages in repair of the integument involve the introduction into the area of clotting proteins, white blood cells, and antibodies from damaged blood vessels. The clotting factors patch the wound together and block the entry of pathogens into the body. As new vessels grow they form a granular tissue, which is followed by the production of new collagen fibers within the dermis. Growth of epithelium is the last step in wound repair. 19. The epidermis is derived from ectoderm, whereas the dermis develops from the deeper mesoderm. 20. With time, stem cells required to regenerate integument become less active, making it more difficult to repair aging tissues. Consequently, the amount of collagen deceases, and elastic fibers lose elasticity, allowing the skin to wrinkle. The activity of hair follicles also decreases, causing thinning of the hair.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Acne is an infection of sebaceous glands by bacteria feeding off of sebum. Sebum production increases during puberty. 2. C Feedback: The stratum corneum of the epidermis is composed of flattened anucleate cells. 3. C Feedback: Since the epidermis is avascular, a wound that involves bleeding must permeate the dermis. Since the wound does not appear deep, it did not damage the entire depth of the dermis.

Answers to “Can You Synthesize What You’ve Learned?” 1. On a cold day, vasoconstriction of dermal blood vessels shunts blood away from the surface of the skin in an effort to retain heat. Deprived of blood supply the surface of the skin may appear pale. When entering back into a warm room, vasodilation allows more blood to reach the surface of the skin, causing a flushed appearance. 2. Acne is an infection of sebaceous glands by bacteria feeding off of sebum. The production of sebum increases during puberty as hormone levels increase. Consequently, adolescents entering puberty often experience an increase in acne due to overactivity of sebaceous glands. 3. The growths on John's face may have been skin cancer. Overexposure of epidermal cells to UV light may damage their DNA allowing them to divide uncontrollably, a hallmark of cancer.

Chapter 7 Answers to “What Did You Learn?” 1. Compact bone consists of a solid, dense mass of bone tissue, whereas spongy bone contains a more porous arrangement of the tissue. 2. Fibrocartilage is located within intervertebral discs, the pubic symphysis, and the menisci of the knee. 3. Bones serve as a reservoir for calcium and phosphate. Calcium is an important component in muscle contraction, nerve conduction, and blood clotting. Phosphate is required for the production of ATP and nucleotides. 4. Most of the bones of the roof of the skull, the scapulae, the sternum, and the ribs are flat bones. 5. The diaphysis is the shaft of a long bone. It consists of a relatively thick cylindrical arrangement of compact bone, lined with spicules of spongy bone, usually surrounding a central medullary cavity. The epiphyses are the knobby ends of long bones. They consist primarily of spongy bone, surrounded by a thin crust of compact bone. 6. The nutrient foramen is an opening within a bone for the nutrient artery and vein as well as innervation. 7. The adult skeleton contains red bone marrow within spongy bone of flat bones in the skull, vertebrae, ribs, sternum, and ossa coxae. 8. Osteoprogenitor cells are the adult stem cells from which produce the remaining cells of bone tissue. Osteoblasts produce osteoid which gives rise to the matrix of bone tissue. Osteocytes are differentiated osteoblast that have become trapped within, and continue to maintain their matrix. Osteoclasts participate in bone resorption, breaking down bone tissue and releasing calcium and phosphate. 9. The matrix of bone tissue consists primarily of organic collagen fibers surrounded by inorganic hydroxyapatite crystals (precipitated calcium phosphate). 10. An osteon consists of several rings of bone tissue, called lamellae, surrounding a central canal. Osteocytes, each surrounded by a small cavity called a lacuna, are located in between the lamellae. Canaliculi run transversely through the lamellae, bridging the lacunae of osteocytes, permitting them to form connections through the crystalline matrix. 11. The matrix of hyaline cartilage does not contain calcium, but does contain a large percentage of water, nearly 80%. Also, unlike bone tissue, mature hyaline cartilage is avascular and does not contain nerves. 12. Appositional growth of cartilage occurs at the periphery of the tissue, along the perichondrium. Interstitial growth occurs from within the matrix. 13. Intramembranous ossification begins during the eighth week of fetal development and produces the flat bones of the skull and face, as well as the clavicles. 14. Endochondral ossification starts with the formation of a periosteal bony collar around embryonic hyaline cartilage. A periosteal bud extends from the periosteum into the cartilage shaft, forming the primary ossification center. Secondary ossification centers then form at the epiphyses of the developing bone. Eventually, bone tissue replaces all of the cartilage except at the epiphyseal growth plates and the articular cartilage. Around the time of puberty the epiphyseal plates are replaced completely by bone tissue. 15. Bones are widened through appositional growth at the periosteum by osteoblasts laying down rings of matrix called circumferential lamellae. 16. Bone remodeling is the removal of old bone tissue and its replacement by new bone tissue. It occurs primarily in response to mechanical stress upon the bone or to stimuli from hormones such as growth hormone, thyroid hormone, or sex hormones. 17. Growth hormone stimulates the growth of epiphyseal plates, thereby causing interstitial growth. Thyroid hormone affects the basal metabolic growth rate of bone cells. 18. UV light absorbed through the skin converts 7-dehydrocholesterol in the blood to vitamin D3. Vitamin D3 is then converted to calcidiol within the liver and then to calcitriol (the active form of vitamin D) in the kidneys.

19. Parathyroid hormone is secreted from the parathyroid glands in response to low levels of calcium in the blood. Parathyroid hormone activates the conversion of calcidiol to calcitriol in the kidneys. Parathyroid hormone and calcitriol act synergistically to increase the release of calcium from bone tissue and to increase the retention of calcium within the kidneys. Calcitriol also facilitates the absorption of calcium from the small intestine. 20. Calcitonin decreases blood calcium levels by decreasing osteoclast activity in the skeleton, thereby inhibiting bone resorption. It also inhibits the reabsorption of calcium from the kidneys, thereby eliminating it in urine. 21. Estrogen is involved in protection of women from osteoporosis. As estrogen levels drop in postmenopausal women, they are more likely to experience osteoporosis. 22. Initially, broken blood vessels in a broken bone form a hematoma. The hematoma is replaced by a fibrocartilaginous callus, which is then replaced by a compact bone, and then finally remodeled. 23. A fibrocartilaginous callus consists of dense irregular connective tissue, although strong, unlike bone tissue it is not capable of bearing weight and can be damaged when pressure is applied.

Answers to “Do You Know the Basics?” 1. D Feedback: Tendons are an extension of muscle tissue and attach muscles to bones. 2. A Feedback: Red bone marrow serves as the site of hemopoiesis. 3. D Feedback: A bone contains dense irregular connective tissue within the periosteum, hyaline cartilage within the articular cartilage, and bone tissue within the matrix of both compact and spongy bone. Therefore it is an organ. 4. C Feedback: The femur, with a diaphysis, medullary cavity, and distinct epiphyses is a long bone. 5. B Feedback: Osteoids are produced by osteoblasts. 6. B Feedback: Lacunae are the small spaces surrounding either osteocytes in bone tissue or chondrocytes in cartilage. 7. C Feedback: Red bone marrow serves as the site of hemopoiesis. 8. A Feedback: The matrix of hyaline cartilage is very similar to that of bone, except it does not contain calcium. 9. B Feedback: Hyaline cartilage 10. A Feedback: Epiphyseal growth plates are replaced by a line of compact bone called the epiphyseal line. 11. The diaphysis is the shaft of a long bone. It consists of a relatively thick cylindrical arrangement of compact bone, lined with spicules of spongy bone, usually surrounding a central medullary cavity. The epiphyses are the knobby ends of long bones. They consist primarily of spongy bone, surrounded by a thin crust of compact bone. A typical long bone consists of a diaphysis separated from one or more epiphyses by either epiphyseal plates of hyaline cartilage, or by epiphyseal lines composed of compact bone. The entire structure is surrounded by dense irregular connective tissue, the periosteum, except at the articular ends where it is covered with hyaline cartilage. 12. Osteoblasts produce osteoid which gives rise to the matrix of bone tissue. They are responsible for the appositional growth of bones. Osteoclasts participate in bone resorption, breaking down bone tissue and releasing calcium and phosphate. Together, osteoblasts and osteoclasts participate in bone remodeling.

13. The osteon is the structural unit of compact bone. It consists of several rings of bone tissue, called lamellae, surrounding a central canal. Osteocytes, each surrounded by a small cavity called a lacuna, are located in between the lamellae. Canaliculi run transversely through the lamellae, bridging the lacunae of osteocytes, permitting them to form connections through the crystalline matrix. 14. Because of the irregular arrangement of tissue within spongy bone, it is able to withstand force from various directions. 15. Appositional growth of cartilage occurs at the periphery of the tissue, along the perichondrium. Interstitial growth occurs from within the matrix. 16. Endochondral ossification starts with the formation of a periosteal bony collar around embryonic hyaline cartilage. A periosteal bud extends from the periosteum into the cartilage shaft, forming the primary ossification center. Secondary ossification centers then form at the epiphyses of the developing bone. Eventually bone tissue replaces all of the cartilage except at the epiphyseal growth plates and the articular cartilage. Around the time of puberty the epiphyseal plates are replaced completely by bone tissue. 17. Growth at epiphyseal plates occurs primarily within the proliferating zone, as chondrocytes divide, and within the hypertrophic zone as the chondrocytes expand. 18. Mechanical stress such as that experienced during weight-bearing exercise induces bone remodeling, consequently contributing to bone mass. 19. Parathyroid hormone is secreted from the parathyroid glands in response to low levels of calcium in the blood. Parathyroid hormone activates the conversion of calcidiol to calcitriol in the kidneys. Parathyroid hormone and calcitriol act synergistically to increase the release of calcium from bone tissue and to increase the retention of calcium within the kidneys. 20. Initially, broken blood vessels in a broken bone form a hematoma. The hematoma is replaced by a fibrocartilaginous callus, which is then replaced by a compact bone, and then finally remodeled.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Red bone marrow contains active hematopoietic cells, which are needed to treat leukemia. In adults, the red marrow is only located within the spongy bone of flat bones, such as the hip. 2. C Feedback: Collagen, a protein, is destroyed with excessive heat, leaving bone tissue dry and brittle. Hypoxyapatite crystals dissolve in acid, leaving behind flexible collagen fibers. 3. B Feedback: Yellow marrow found within the medullary cavity of long bones is rich in adipose tissue. 4. A Feedback: The fusion of the epiphyses to the diaphysis occurs in response to hormones produced at puberty, thus providing an indication as to the age of the skeleton. 5. C Feedback: Chondrocytes form attacks within the zone of proliferation. These then become enlarged within the zone of hypertrophy.

Answers to “Can You Synthesize What You’ve Learned?” 1. Removal of the parathyroid glands would prevent the person from responding to decreases in blood calcium and prevent the release of parathyroid hormone. Maintaining the parathyroid glands after the removal of the thyroid gland would significantly improve the person’s ability to regulate blood calcium levels. 2. Mechanical stress such as that experienced during weight-bearing exercise induces bone growth, consequently contributing to bone mass. When bones are immobilized to facilitate repair they are not experiencing stress. Consequently, the amount of bone resorption exceeds the amount of interstitial and appositional growth, thereby weakening the bone.

3. Elise’s history indicates numerous factors that can contribute to decreased bone mass and subsequent difficulty in bone repair. Due to a lack of activity and physical interactions with other children her developing bones may have experienced less mechanical stress during a formative developmental period, severely affecting bone mass. Spending most of her time indoors, she may have a deficiency in vitamin D, because of her limited exposure to UV light. Consumption of soft drinks also decreases bone density, in concert with the other factors, leaving her susceptible to damage and prolonged repair.

Chapter 8 Answers to “What Did You Learn?” 1. Foramina and fissures are both openings. A foramen is rounded whereas a fissure is elongated. 2. The axial skeleton primarily serves to provide a framework for and protection of internal organs, as well as hemopoiesis. It consists of the skull, vertebral column, and thoracic cage. 3. The cranium of the skull consists of the frontal, parietal, occipital, ethmoid, sphenoid, and temporal bones. The zygomatic, lacrimal, nasal, inferior nasal conchae, maxillae, vomer, mandible, and palatine bones comprise the face. 4. The frontal bones, maxillae, nasal bones, zygomatic bones, and mandible are the predominant bones visible from the anterior of the skull. 5. The sphenoid and temporal bones comprise the middle cranial fossa, which houses the temporal lobes of the brain and the pituitary gland. 6. The lambdoid suture is the articulation between the occipital and parietal bones. It is the last cranial suture to fuse, usually by age 40. 7. The palatine, maxillae, and zygomatic bones form the floor of the orbit of the eye. 8. The maxillary, sphenoid, ethmoid, and frontal bones contain the paranasal sinuses. 9. The malleus, incus, and stapes are auditory ossicles located within the petrous portion of the temporal bone. 10. Generally, male skulls have a more predominant supercilliary arch and a more sloping frontal bone than female skulls. The female skull will likely have a sharper supraorbital margin, a more triangular mental protuberance, a smoother, less prominent occipital protuberance, and a more obtuse mandibular angle. 11. The posterior and anterior are the largest of the fontanelles, closing by 9 and 15 months of age, respectively. 12. The five lumbar vertebrae comprise the “small” of the back. 13. The cervical and lumbar curvatures of the spine are secondary curvatures that appear after birth. 14. Transverse foramina, which contain the vertebral artery and vein, are located in the transverse processes of cervical vertebrae. The vertebral foramen is located posterior to the body of a vertebra and contains the spinal cord and meninges. The intervertebral foramina are located in between the pedicles of consecutive vertebra and allow for passage of spinal nerve roots joining the spinal cord. 15. The atlas lacks a body and elongated superior articular facets for articulation with the occipital condyles of the skull. The axis has a superior projection called the dens which serves as a pivot point for the atlas. 16. The sternal angle is the articulation between the manubrium and the body of the sternum. It is located at the level of the articulation of the second rib with the sternum. 17. The head of the rib articulates with costal facets on the bodies of consecutive vertebrae. The tubercle of the rib articulates with the transverse costal facet of the inferior vertebra. 18. The lower limbs are well suited for supporting weight and propulsion when walking. In contrast, the upper limbs are suited for dexterous activities such as grasping objects and handling tools. 19. The sternal end of the clavicle is pyramidal in shape, whereas the acromial end is broader and flatter. 20. The supraspinous fossa contains the supraspinatus muscle, the infraspinous fossa contains the infraspinatus muscle, and the subscapula fossa contains the subscapularis muscle. 21. The anatomical neck of the humerus is located in between the head and tubercles. The surgical neck is located distal to the anatomical neck at the site of the former epiphyseal plate, at the start of the diaphysis of the bone.

22. The capitulum articulates with the head of the radius and the trochlea articulates with the trochlear notch of the ulna. 23. The radius and ulna both have an interosseous border from which extends the interosseous membrane. 24. When pronated, the distal portion of the radius is crossed over the ulna and the hand faces posteriorly. 25. The carpus is composed of the trapezium, trapezoid, capitate, hamate, scaphoid, lunate, triquetrum, and pisiform bones. The scaphoid is the most common carpal bone to be broken, which may lead to damage of blood vessels and subsequent avascular necrosis of the bone. 26. The ilium, ischium, and pubis fuse to form the os coxae. 27. The ischial tuberosities are located on the posterolateral border of the ischium. They are also called the “sits bone” because they support the weight of the body when sitting. 28. The pelvic inlet is the superior opening into the pelvis, whereas the pelvic outlet is the inferior opening. 29. The female pelvis usually has a longer, more triangular pelvis, a more convex subpubic angle, and a wider and shallower sciatic notch. Generally, the female pelvis is shallower and wider allowing for passing of an infant’s head through the birth canal. 30. The symphysial surface of a young adult is billowed and lacks a well-formed rim. With age, the rim becomes pronounced and the surface concave. With advanced age, however, the rim begins to break down. 31. The greater trochanter is located lateral to the neck and shaft of the femur. The lesser trochanter is located on the femur’s posterolateral surface. Both trochanters serve as sites of attachment of the gluteal muscles. 32. The articular surface of the patella articulates with the patellar surface of the femur. 33. The tibia and fibula both have an interosseous border from which extends the interosseous membrane. 34. The tibia transduces the weight of the body to the foot. It is the only weight-bearing bone of the crural region. 35. The tarsals consist of the calcaneus, talus, navicular, cuboid, medial cuneiform, lateral cuneiform, and intermediate cuneiform bones. 36. The arches of the foot help to support the weight of the body, as well as ensure adequate blood supply and innervation to the foot. 37. Embryonic hand and foot plates develop longitudinal thickenings called digital rays, which are eventually removed by apoptosis leaving behind distinct digits.

Answers to “Do You Know the Basics?” 1. A Feedback: Both the ethmoid bone and the vomer contribute to the bony portion of the nasal septum. 2. C Feedback: The mandibular condyle articulates with the temporal bone at the temporomandibular joint. 3. A Feedback: The coronal suture connects the frontal bone to the paired parietal bones. 4. B Feedback: Fontanelles do not fuse until well after birth, thereby permitting movement of the cranial bones during childbirth, facilitating the process. 5. B Feedback: The bodies of cervical and lumbar vertebrae are kidney shaped. The bodies of thoracic vertebrae are heart shaped. 6. B Feedback: The female subpubic angle is usually greater than 100 degrees.

7. D Feedback: The olecranon fossa is located on the posterior distal portion of the humerus, positioned to receive the olecranon process which is located on the posterior aspect of the ulna. 8. C Feedback: The supraspinous and infraspinous fossae are located on either side of the spine of the scapula. 9. B Feedback: Both the medial and lateral condyles of the femur articulate with the tibia, forming part of the architecture of the knee joint. 10. B Feedback: The ischial tuberosities are located on the posterolateral border of the ischium. They are also called the “sits bone” because they support the weight of the body when sitting. 11. Sutures are immovable joints between the bones of the skull. Because they do not fully fuse until adulthood, they permit growth and expansion of the skull during development. 12. The medial wall of the orbit of the eye is composed of the frontal process of the maxilla, the lacrimal bone, and the orbital plate of the ethmoid bone. The lateral aspect of the orbit of the eye is composed of the zygomatic process of the frontal bone, the greater wing of the sphenoid bone, and the orbital surface of the zygomatic bone. The zygomatic bone, the orbital process of the maxilla, and the orbital process of the palatine bone comprise the floor of the orbit of the eye. 13. Aside from lightening the skull, the paranasal sinuses complement the functions of the nasal cavity by humidifying and warming inspired air. 14. The articulation between the occipital condyles of the skull and the elongated superior articular facets of the atlas permit for a slight amount of flexion and extension at the joint. The articulation of the dens of the axis with the atlas permits for a slight lateral rotation. 15. True ribs (ribs 1–7) articulate with the sternum through individual costal cartilage attachments. The costal cartilage of ribs 8–10 attach to the cartilage of rib 7 and are therefore considered false ribs. Ribs 11 and 12 do not articulate with the sternum. They are also considered false ribs because they lack a direct attachment. Also appropriately, they are referred to as floating ribs. 16. The pelvic girdle consists of the os coxae, articulating with the sternum posteriorly and together at the pubic symphysis anteriorly. The pectoral girdle consists of the scapula and clavicle. Each girdle has a socket for either the head of the humerus or the head of the femur, forming multiaxial ball-and-socket joints. 17. The anatomical neck of the humerus is located in between the head and tubercles. The surgical neck is located distal to the anatomical neck at the site of the former epiphyseal plate, at the start of the diaphysis of the bone. The surgical neck is more likely to be broken than the anatomical neck. 18. The true pelvis lies inferior to the pelvic brim, and is completely enclosed by the bones of the pelvis. The false pelvis is located above the pelvic brim, below the ala of the ilium. 19. The arches of the foot help to support the weight of the body, as well as ensure adequate blood supply and innervation to the foot. 20. The limb buds form from the lateral plate of the mesoderm, and are covered by endoderm. The upper limb buds appear about 4 weeks into fetal development, followed by the lower buds a few days later. Formation of an apical ectodermal ridge signals underlying tissues to develop. At 6 weeks of development hand and foot plates form, and future digits are delineated by digital rays. The tissue in between the digital rays is removed by apoptosis at about 8 weeks of fetal development, leaving behind distinct digits.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Although both the humerus and femur have a rounded head, the femur has an elongated neck but the humerus does not. 2. A Feedback: The clavicle is S-shaped. It is the site of articulation of the arm with the axial skeleton and may be damaged during a fall.

3. B Feedback: Generally, male skulls have a more predominant supercilliary arch and a more sloping frontal bone than female skulls. Whereas the female skull will likely have a sharper supraorbital margin, a more triangular mental protuberance, a smoother, less prominent occipital protuberance, as well as a more obtuse mandibular angle. 4. B Feedback: The female pelvis usually has a longer, more triangular pelvis, a more convex subpubic angle, and a wider and shallower sciatic notch. Generally, the female pelvis is shallower and wider allowing for passing of an infant’s head through the birth canal. 5. C Feedback: From the presence of permanent teeth and fused epiphyseal plates you could predict the victim’s age to be well past puberty. However, the lack of ossified sutures in the skull or of a pronounced rim around the pubic symphysis would indicate that she was a young adult.

Answers to “Can You Synthesize What You’ve Learned?” 1. Passage through the birth canal can often distort the shape of an infant’s head due to the presence of fontanelles which make the cranium slightly more malleable. After birth, the same fontanelles allow the cranial bones to accommodate the quickly growing newborn brain. 2. Thalidomide is a teratogen that interferes with fetal development by inhibiting the expression of numerous genes, including those involved in development of vasculature in the limbs. 3. The shape of the pelvic outlet, the proportions of the greater sciatic notch and the obturator foramen, as well as the shape of the ischial spine may be used as indicators of the sex. Age-related changes to the symphysial surface of the pubis may be used to determine the age; and the extent of osteoporosis may be an indicator of the relative health of the individual.

Chapter 9 Answers to “What Did You Learn?” 1. There is an inverse relationship between the stability of a joint and its range of motion. The more possible movement there is at a joint, the more likely it is to sustain damage. 2. Not all fibrous joints are synarthroses. Synarthrotic joints are by definition immobile, and fibrous joints are simply held together by collagen. These two criteria are not mutually exclusive. Some fibrous joints such as sutures are synarthrotic, others such as the interosseous membrane between the radius and ulna are amphiarthrotic. 3. The periodontal ligaments are the only gomphoses in the body. They are located within the alveolar sockets of the mandible and maxilla, and they are synarthrotic. 4. Sutures are synarthrotic joints between the bones of the skull. They are held together by collagen fibers. 5. Syndesmoses are amphiarthrotic. They permit a limited range of movement. 6. Synchondroses are held together by hyaline cartilage. They may be found within the epiphyseal plates of children or the costal cartilage attaching ribs to the sternum. 7. Symphyses are optimized for absorbing pressure and compression forces, and are primarily synarthrotic. 8. All synovial joints are diarthrotic. They consist of an articular capsule surrounding a joint cavity, which contains synovial fluid. Articular cartilage is also present at the end of each bone involved in the joint, as are numerous ligaments, nerves, and blood vessels. 9. Synovial fluid lubricates and nourishes articular cartilage at a joint. It can also act as a shock absorber distributing forces during compression. 10. Plane joints are capable of uniaxial side-to-side gliding movements. Both hinge and pivot joints are also considered uniaxial since they only move along one plane. Condyloid and saddle joints are biaxial because they permit movement in two dimensions. Lastly, ball-and-socket joints are multiaxial because they are capable of movement in three dimensions. 11. The effort arm is the length of the lever from the fulcrum to the point where force (effort) is applied. The resistance arm is the length of the lever from the fulcrum to the point where resistance is applied. 12. In a first-class lever, the fulcrum is located between the resistance and effort. In a second-class lever, the resistance is between the fulcrum and effort. In a third-class lever, effort is applied between the resistance and the fulcrum. 13. Gliding movements occur within plane joints, such as those in between the carpals or tarsals. 14. Flexion decreases the angle at joint along an anterior-posterior plane, whereas extension increases the angle along an anteriorposterior plane. Circumduction is a sequence of movements in which the proximal end of an appendage remains relatively stationary while the distal end makes a circular motion. 15. Pronation is the medial rotation of the forearm so that the palm of the hand is directed posteriorly, crossing the radius over the ulna. 16. Inversion and eversion occur with the tarsals of the food. The sole of the foot is turned medially during inversion, and laterally during eversion. 17. The temporomandibular joint is both a plane joint, capable of gliding movement, and a hinge joint, capable of elevation and depression of the mandible. 18. The glenohumeral joint consists of a shallow cup with minimal support from ligaments. Most of the stability at the shoulder comes from the muscles of the rotator cuff. This provides for a wide range of motion, but sacrifices stability. 19. The annular ligament holds the head of the radius against the radial notch of the ulna. Subluxation of the elbow occurs more commonly in children because of the loose positioning of the still developing head of the radius, within a thin annular ligament.

20. The glenohumeral joint has a far greater range of motion than the hip. However, the hip is much more stable and less likely to be dislocated. 21. The anterior cruciate ligament prevents hyperextension of the knee, while also preventing the tibia from moving too far anteriorly, relative to the femur. Conversely, the posterior cruciate ligament prevents hyperflexion of the knee, while also preventing posterior movement of the tibia, relative to the femur. 22. The talocrural joint is formed by the articulation of the talus with both the tibia and fibula. The joint permits dorsiflexion and plantar flexion at the ankle. 23. Changes to joints begin early with the closure of epiphyseal plates, and continue well into adulthood with the ossification of the sutures in the skull. Osteoarthritis is also often incurred with age, leading to degradation of the joints.

Answers to “Do You Know the Basics?” 1. C Feedback: The glenohumeral joint is a multiaxial ball-and-socket joint. It is less stable than other ball-and-socket joints, such as the hip; however, it does have a far wider range of motion. 2. C Feedback: The sole of the foot is turned medially during inversion, and laterally during eversion. 3. B Feedback: Synostoses are completely ossified sutures. 4. C Feedback: The anterior cruciate ligament prevents hyperextension of the knee, while also preventing the tibia from moving too far anteriorly, relative to the femur. 5. C Feedback: The glenohumeral joint consists of a shallow cup with minimal support from ligaments. Most of the stability at the shoulder comes from the muscles of the rotator cuff. This provides for a wide range of motion, but sacrifices stability. 6. C Feedback: In a third-class lever such as the knee, effort is applied between the resistance and the fulcrum. 7. A Feedback: The metacarpophalangeal joints are condyloid in shape, in that they possess a shallow cup with an oval articular surface, which permits movement in two axes. 8. D Feedback: The ligament of the head of the femur, the ligamentum teres, contains an artery running to the femur, but does not provide for stability at the hip. 9. D Feedback: Synovial fluid lubricates and nourishes structures within the synovial joint. It can also act as a shock absorber distributing forces during compression. 10. D Feedback: The talocrural joint is formed by the articulation of the talus with both the tibia and fibula. The joint permits dorsiflexion and plantar flexion at the ankle. 11. Stability of a joint is a function of three components: the shape of articular surfaces involved, tension produced by ligaments, and muscle tone. The stability provided by these three components decreases with increased mobility at the joint. 12. Fibrous joints such as sutures and syndesmoses are held together by collagen. Cartilaginous joints such as synchondroses or symphyses, are held together by either hyaline cartilage or fibrocartilage, respectively. 13. Synarthrotic joints are immobile. The gomphosis comprising the periodontal ligament and the sutures of the skull are examples of synarthrotic joints. Synchondroses, such as costal cartilage or epiphyseal plates composed of hyaline cartilage, are also synarthrotic.

14. Both hinge and pivot joints are uniaxial diarthroses. Hinge joints such as the elbow, knee, or the interphalangeal joints consist of the junction of the convex portion of one bone, articulating with the concave portion of another bone. Within pivot joints such as the humeroradial joint or the atlantoaxial joint, a bone with a rounded surface fits into a ring formed by a ligament and another bone. 15. In a first-class lever, the fulcrum is located between the resistance and effort. In a second-class lever, the resistance is between the fulcrum and effort. In a third-class lever, effort is applied between the resistance and the fulcrum. 16. From standard anatomical position, abduction moves a feature away from the axis of the body; adduction brings the feature toward the body, back to standard anatomical position. Pronation involves the rotation of the head of the radius within the annular ligament of the elbow, resulting in the crossing of the radius over the ulna so that the palm faces to the posterior. Supination returns the pronated limb back to standard anatomical position. 17. The ball-and-socket joint of the shoulder consists of the head of the radius articulating at the glenoid fossa of the scapula, which is surrounded along its periphery by the glenoid labrum. Stabilizing the joint superficially are the coracoacromial and coracohumoral ligaments, as well as three thickened portions of the articular capsule of the shoulder, collectively called the glenohumeral ligaments. Although the glenoid labrum and surrounding ligaments provide some stability to the joint, the most important factor to stability at the shoulder are the tendons of the rotator cuff muscles: the infraspinatus, supraspinatus, subscapularis, and teres minor muscle. 18. The radial collateral ligament is responsible for stabilizing the elbow at its lateral surface, the ulnar collateral ligament stabilizes the medial side of the elbow, and the anular ligament surrounds the neck of the radius and binds the proximal head of the radius to the ulna. 19. The tibial collateral ligament stabilizes the medial surface of the knee, preventing the leg from moving laterally, relative to the femur. The fibular collateral ligament stabilizes the lateral surface of the knee, preventing the leg from moving medially, relative to the thigh. Because the tibial collateral ligament prevents excessive medial movement of the tibia, relative to the femur, it experiences the brunt of a lateral force applied to the knee. 20. Osteoarthritis is caused by wear and tear of articular cartilage within a joint. With time, the bony surfaces may start to rub causing inflammation, pain, and further damage.

Answers to “Can You Apply What You’ve Learned?” 1. A Feedback: The anular ligament holds the head of the radius against the radial notch of the ulna, and can be easily subluxated. 2. B Feedback: Subluxation of the elbow occurs more commonly in children because of the loose positioning of the still developing head of the radius, within a thin anular ligament. 3. C Feedback: In this case, subluxation of the elbow allowed the head of the radius to move laterally out of the anular ligament. 4. D Feedback: The lateral ligament prevents overinversion at the ankle. Likewise, overinverting the foot at the ankle can damage the lateral ligament. 5. B Feedback: The posterior cruciate ligament becomes taut on flexion, and prevents hyperflexion of the knee joint.

Answers to “Can You Synthesize What You’ve Learned?” 1. Erin has dislocated her shoulder, possibly tearing the capsule of the glenohumeral joint as the head of the humerus moved inferior, out of the glenoid cavity. 2. The knee is extremely susceptible to damage from a lateral impact. Within the knee, the tibial collateral ligament prevents excessive medial movement of the tibia, relative to the femur. Hence, it will experience the brunt of a lateral force applied to the knee. The tibial collateral ligament is directly attached to the medial meniscus of the knee, and damage to the ligament can also result in damage to the meniscus. 3. The doctor is examining Jackie’s temporomandibular joint. Wear and tear within the joint can cause inflammation, damage to the articular disc, and pain. Dislocation of the articular disc can be perceived as a clicking sound, when the jaw is opened and closed.

Chapter 10 Answers to “What Did You Learn?” 1. Skeletal muscle tissue is responsible for body movement, maintenance of posture, structural support, storage and movement of minerals, and heat production. 2. Contractility implies that muscle tissue has the capacity to decrease in length. Elasticity means the muscle tissue will recoil to its original shape once the contraction stops. Extensibility implies that the muscle can be stretched back to its original shape by the action of an opposing muscle. 3. Endomysium surrounds individual muscle fibers, perimysium surrounds muscle fascicles, and epimysium surrounds the entire muscle. Deep fascia separates individual muscles from each other, whereas superficial fascia separates skeletal muscles from the skin. 4.

5. Muscle > fascicle > muscle fiber > myofibril > myofilament 6. A single motor neuron and the muscle fibers it controls are called a motor unit. The number of muscle fibers in a motor unit determines the degree of precision of control. 7.

8. The binding of Ca2+ to synaptic vesicles triggers the merging of synaptic vesicles with the synaptic knob plasma membrane resulting in exocytosis of acetylcholine into the synaptic cleft. 9. Excitation-contraction coupling refers to the series of events that begins with the excitation of the sarcolemma in response to stimulation by a neurotransmitter, and results in the release of calcium ions from the sarcoplasmic reticulum. 10. Opening of sodium channels along the sarcolemma in response to a neurotransmitter generates an action potential along the surface of the muscle fiber. The action potential is carried deep into the cell along T-tubules. Within the cell the action potential triggers the release of calcium ions from cisternae of the sarcoplasmic reticulum. 11. Ca2+ binds to troponin in muscle thin filaments, causing a conformational change in troponin, which in turn affects shape of the entire troponin-tropomyosin complex, exposing myosin binding sites. 12. Crossbridge cycling begins with crossbridge formation, which is followed by a power stroke and a subsequent release of myosin from actin. The myosin head then undergoes a conformational change and resets, and the cycle repeats. 13. Binding of ATP to the myosin head causes the release of myosin from actin. The hydrolysis of ATP then provides the energy for the conformational change and reset of the myosin head. 14. Acetylcholinesterase degrades acetylcholine in the synaptic cleft, decreasing its effect, and consequently the excitation of the muscle fiber. Without further stimulation, calcium channels within the sarcoplasmic reticulum close. The Ca2+ ATPase is then able to pump calcium ions out of the cytosol, back into the sarcoplasmic reticulum. 15. ATP is generated when creatine kinase transfers Pi from creatine phosphate to ADP, yielding creatine and ATP. 16. The immediate energy required for muscle contraction is provided for by the phosphagen system of preexisting phosphatecontaining molecules, such as existing intracellular stores of ATP and creatine phosphate. Anaerobic respiration then provides a brief supply of ATP, until aerobic respiration is able to generate even more. 17. Oxygen debt is the amount of additional oxygen required following exercise to restore pre-exercise conditions. It is necessary to replace oxygen on hemoglobin molecules in the blood and myoglobin molecules in muscle, to replenish glycogen stored in muscle fibers, to replenish the phosphagen system, and to convert lactic acid back to glucose in the liver. 18. Compared to slow-twitch fibers, fast-twitch fibers have a myosin with a faster ATPase function, faster conduction along their sarcoplasmic reticulum, as well as faster calcium release and reuptake. Oxidative fibers use aerobic cellular respiration to produce ATP; glycolytic fibers are only capable of anaerobic respiration. 19. Slow oxidative fibers produce contractions that are slower and less powerful. However, they can contract over long periods of time without fatigue because ATP is supplied primarily through aerobic cellular respiration. 20. Slow oxidative fibers are predominant in many postural muscles, which are required to contract for prolonged durations. 21. The latent period corresponds to the time from the point of excitation of a muscle fiber, until the point at which the contraction starts. Muscle tension then increases during the contraction period, as sarcomeres shorten. Decreased calcium levels then cause the release of myosin from actin, during the relaxation period. 22. Recruitment is the increase in muscle tension, caused by consecutive stimuli of a motor unit. This permits precise control of force generated by a muscle by regulating the number of motor units involved in a contraction. 23. Summation results from the continuous stimulation of a muscle at a high enough frequency, so that relaxation is not possible in between stimuli. This results in a summation of contractile forces, culminating in a prolonged contraction of maximum strength called tetany. 24. Muscle tone is the resting tension in a muscle generated by involuntary nervous stimulation of the muscle. It is required to maintain tension and the position of a joint, without producing movement. 25. Flexion at the elbow caused by contraction of the biceps brachii would be a concentric isotonic contraction.

26. When lifting objects by bending solely at the waist, muscle contraction begins with overly stretched sarcomeres, with limited overlap between actin and myosin fibers. This results in a weaker contraction. Bending at both the knees and waist permits the muscles of the back to begin the contraction from an optimal position, with well-overlapping actin and myosin fibers, thereby generating greater force. 27. Muscle fatigue may be triggered at the neuromuscular junction due to either insufficient levels of calcium or a low number of synaptic vesicles in the presynaptic neuron. Changes in sodium or potassium ion concentrations may affect excitation-contraction coupling, inhibiting the action potential along the sarcolemma, also causing muscle fatigue. An excess of intracellular Pi may also cause muscle fatigue by interfering with the release of myosin from actin during crossbridge cycling. 28. In hypertrophy, each muscle fiber develops more myofibrils, and each myofibril develops more myofilaments, resulting in increased fiber diameter. 29. With age and decreased use, skeletal muscles begin to lose both myofilaments and muscle fibers. As myoglobin and glycogen stores decrease with age so do muscle strength and resistance to fatigue. Over time elasticity is also lost as muscle tissue is replaced by an accumulation of dense irregular connective tissue. The population of satellite cells within the muscle also decreases. 30. Cardiac muscle is composed of individual cells, whereas skeletal muscle is composed of large, fused, multinucleated cells. Cardiac muscle is not innervated directly by the central nervous system and is therefore involuntary. Lastly, unlike skeletal muscle, individual cells of cardiac muscle are joined together by intercalated discs, containing gap junctions which permit communication between individual cells. 31. Smooth muscle may be found within the walls of hollow organs such as blood vessels, bronchioles, the alimentary canal, the ureters, the uterus, ciliary body of the eye, the iris of the eye, or the arrector pili muscles in the skin. 32. Although smooth muscle fibers have both thick and thin filaments, they are not precisely aligned, so no striations or sarcomeres are visible. Dense bodies are small concentrations of protein scattered throughout the sarcoplasm of the smooth muscle fiber and on the inner face of the sarcolemma. Thin filaments are attached to dense bodies by elements of the cytoskeleton. 33. In smooth muscle, calcium ion binds to calmodulin forming the Ca2+-calmodulin complex, which activates the myosin light-chain kinase, which is then able to phosphorylate the smooth muscle myosin heads. The myosin heads are deactivated through dephosphorylation by myosin light-chain phosphatase. 34. Smooth muscle contraction begins with the release of calcium ions into the sarcoplasm, in response to stimulation, resulting in formation of the Ca2+-calmodulin complex and subsequent activation of the myosin light-chain kinase (MLCK). MLCK phosphorylates the myosin head, allowing it to bind to actin. Hydrolysis of ATP permits the power stroke which slides the actin past the thick filaments. This sliding results in a pull on the attached dense bodies anchored to the intermediate filaments of the cytoskeleton and the dense plaques attached to the sarcolemma. The anchoring filaments move inward and the entire smooth muscle cell shortens. 35. The latchbridge mechanism, found only in smooth muscle, permits smooth muscle cells to remain contracted after calcium has been removed, without further hydrolysis of ATP. This results in a prolonged duration of contraction with low energy requirements. Thus smooth muscle is relatively resistant to fatigue. It also exhibits a broader length-tension curve than skeletal muscle. Because of the positioning of myosin heads along the entire length of the thick filaments in smooth muscle, it is capable of generating a forceful contraction regardless of whether it is compressed or stretched out. 36. Smooth muscle may be stimulated by the autonomic nervous system, through the stress-relaxation response elicited by stretching of the muscle, or by endocrine hormones. It may also be stimulated by local factors within the tissue, such as decreased pH, low oxygen levels, or high levels of carbon dioxide. Smooth muscle may also be stimulated by pacemaker cells from within the tissue. 37. The stress-relaxation response occurs when smooth muscle is “stressed” by being stretched. It responds by contracting, but after a given period of time, it relaxes. 38. Single-unit smooth muscle usually consists of several sheets of cells, linked together by gap junctions so that they may contract as one unit. This is a useful arrangement for the walls of hollow organs where the entire organ must contract in unison. Multiunit smooth muscle consists of individual muscle cells innervated by neurons, and permits more precise control over muscle contractions, such as in muscles within the eye.

Answers to “Do You Know the Basics?” 1. D Feedback: A muscle fiber is an individual cell. It contains contractile organelles called myofibrils and is surrounded by a connective tissue covering called the endomysium. 2. B Feedback: The plasma membrane of a skeletal muscle fiber is called the sarcolemma. 3. C Feedback: In skeletal muscle fibers, Ca2+ is stored within the cisternae of the sarcoplasmic reticulum. 4. A Feedback: Tendons consist of dense regular connective tissue, and connect muscles to bones. 5. A Feedback: The action potential, traveling along the sarcolemma of a muscle fiber, is carried deep into the cell along T-tubules. Within the cell the action potential then triggers the release of calcium ions from cisternae of the sarcoplasmic reticulum. 6. B Feedback: The I band represents the region where actin is present, but does not overlap with myosin. As the sarcomeres contract, the extent of overlap between actin and myosin increases, and consequently the I band shortens. 7. D Feedback: During a concentric contraction, myofibrils contract, resulting in contraction of muscle fibers, and the subsequent contraction of the muscle. 8. C Feedback: Troponin undergoes a conformational change in response to Ca2+, sequestering calcium ions from the sarcoplasm back into the sarcoplasmic reticulum, then permitting the rearrangement of troponin back to its resting state. 9. C Feedback: In skeletal muscle some of the energy required for muscle contraction is provided for by the phosphagen system of preexisting phosphate-containing molecules, such as creatine phosphate. This mechanism is unique to muscle tissue. 10. D Feedback: With age, skeletal muscles begin to lose both myofilaments and muscle fibers. As myoglobin and glycogen stores decrease with age so do muscle strength and resistance to fatigue. Over time elasticity is also lost as muscle tissue is replaced by an accumulation of dense irregular connective tissue. The population of satellite cells within the muscle also decreases. 11. A muscle fiber is an individual cell. Myofibrils are the contractile organelles within the muscle fiber and consist of myofilaments, actin and myosin. The myofilaments within the myofibril are arranged in a series of repeating contractile units called sarcomeres. 12.

13. The ratio of motor neurons to muscle fibers in a motor unit corresponds to the type of movement the muscle is capable of performing. This ratio is greater in muscles that require precise control over fine movements, such as those that control the movement of the eye. Conversely, postural muscles possess much larger motor units, with numerous muscle fibers stimulated by fewer neurons. 14. c. An action potential is propagated along the sarcolemma and transverse tubules. b. Calcium ions are released from the sarcoplasmic reticulum and bind to troponin. f. Tropomyosin molecules are moved off active sites on actin. d. Myosin binds to actin, forming crossbridges. a The myosin head pivots toward the center of the sarcomere. e. Myosin heads bind ATP molecules and detach from actin. g. ATPase splits ATP, providing energy to reset the myosin head.

15. The immediate energy required for muscle contraction is provided for by the phosphagen system of preexisting phosphatecontaining molecules, such as existing intracellular stores of ATP, creatine phosphate which is able to donate a phosphate to ADP to yield ATP, or myokinase which is capable of transferring a phosphate to one ADP molecule to another to produce ATP. Anaerobic respiration then provides a brief supply of ATP through the hydrolysis of glucose, until aerobic respiration is able to generate even more. 16. Athletes who perform quick bursts of movement require muscles with a larger proportion of fast-twitch fibers rather than slowtwitch fibers. Fast-twitch fibers initiate a contraction more quickly upon stimulation, and produce a stronger contraction with a shorter duration. Slow-twitch fibers would be optimum for slow prolonged or repetitive movements. 17. A skeletal muscle fiber stimulated when it is at a normal resting length generates a maximum contractile force because there is optimal overlap of thick and thin filaments. Weaker contractions in muscles that are already contracted occur because the thick filaments are close to the Z discs, and sliding filaments are limited in their movement. Weaker contractions occur in muscles that are overly stretched because there is minimal thick and thin filament overlap for crossbridge formation. 18. The myosin heads of smooth muscle have modifications that allow them to “latch on” to the actin of thin filaments. This latchbridge mechanism provides the means of maintaining muscle contraction without use of additional ATP. Inactivation by the myosin light-chain phosphatase is required for relaxation of smooth muscle. 19. The stress-relaxation response occurs when smooth muscle is “stressed” by being stretched. It responds by contracting, but after a given period of time, it relaxes even if the stimulus is still present. 20. Single-unit smooth muscle usually consists of several sheets of cells, linked together by gap junctions so that they may contract as one unit. This is a useful arrangement for the walls of hollow organs where the entire organ must contract in unison, such as the organs of the digestive, urinary, or reproductive systems. Multiunit smooth muscle consists of individual muscle cells innervated by neurons, and permits more precise control over muscle contractions. It is present in the muscles of the iris and ciliary bodies of the eye, as well as within the arrector pili muscles of the skin.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Blocking the release of neurotransmitter from the presynaptic vesicle would inhibit stimulation of the muscle fiber. Since no neurotransmitter would be released, no subsequent action potential would be elicited along the muscle fiber. 2. D Feedback: Athletes who perform quick bursts of movement require muscles with a larger proportion of fast-twitch fibers rather than slow-twitch fibers. Fast-twitch fibers initiate a contraction more quickly upon stimulation, and produce a stronger contraction with a shorter duration. 3. A Feedback: K+ and Na+ are important components in generating the action potential along the skeletal muscle fiber. Ca2+ is required to stimulate the release of neurotransmitters at the neuromuscular junction. Calcium is also required to induce the conformational change in troponin, which allows the attachment of myosin to actin. F- is not a critical component in muscle contraction or neuron function.

4. B Feedback: The release of myosin from actin requires ATP. Upon death, when ATP is no longer available, skeletal muscles become fixed in a contracted state called rigor mortis. 5. C Feedback: At the start of exercise, muscles are initially powered by ATP from the phosphogen system and anaerobic respiration. Prolonged exercise, however, requires aerobic respiration. Increased cardiovascular health allows a person to exercise more vigorously for longer durations.

Answers to “Can You Synthesize What You’ve Learned?” 1. The immediate energy required for muscle contraction is provided for by the phosphagen system of preexisting phosphatecontaining molecules, such as existing intracellular stores of ATP and creatine phosphate. Anaerobic respiration then provides a brief supply of ATP, until aerobic respiration is able to generate even more. When running a short 400-meter race, most of the energy is therefore provided by the phosphagen system and anaerobic respiration. For a longer 1-mile run, aerobic respiration eventually ramps up and provides ATP. 2. Repetitive exercise causes muscle hypertrophy due to an increase in the amounts of myofilaments and myofibrils present within muscle fibers, which results in increased muscle tone. 3. Muscle atrophy results from a lack of muscle use, resulting in a decrease in muscle fiber size and tone.

Chapter 11 Answers to “What Did You Learn?” 1. The less moveable attachment of a muscle is called its origin. The more moveable attachment of the muscle is its insertion. Usually, the insertion is pulled toward the origin. 2. Parallel muscles have a lot of endurance but are relatively weaker than pennate muscles. 3. The agonist is the prime mover for an action and generates the majority of the force. The synergist facilitates the movement produced by the agonist by either contributing tension or stabilizing the bones involved. 4. A description of the shape of a muscle may be incorporated into its name: A deltoid muscle is triangular in shape, orbicularis implies that the muscle has fibers arranged in a circle, a rhomboid muscle has the shape of a rhomboid, and the trapezius muscle is shaped like a trapezoid. The length of the muscle may also be incorporated into the nomenclature: The terms longus and longissimus refer to relatively long muscles and brevis refers to short muscles. 5. The gluteus maximus gets its name from (1) the gluteal region of the body (buttocks) = gluteus, and (2) the size of the muscle = maximus (largest). 6. The levator anguli oris, zygomaticus major, zygomaticus minor, and risorius muscles all contribute to smiling. 7. The depressor anguli oris contracts to pull the corners of the mouth inferiorly when frowning. 8. The lateral rectus muscle abducts the eye. 9. The pterygoid muscles are responsible for protraction and side-to-side movement of the mandible. The medial pterygoid muscle may also elevate the mandible. 10. The extrinsic tongue muscles are used in various combinations to accomplish the precise, complex, and delicate tongue movements required for proper speech and manipulating food within the mouth. 11. The digastric, geniohyoid, mylohyoid, and stylohyoid muscles are suprahyoid muscles. All four are capable of elevating the hyoid bone. 12. The sternocleidomastoid and scalene muscles flex the neck. Extension at the neck may be accomplished by the splenius capitis, splenius cervicis, longissimus capitis, rectus capitis posterior major, or rectus capitis posterior minor muscles. 13. The erector spinae is the largest muscle mass in the back. The muscles of the erector spinae consist of three groups of muscles: iliocostalis (located laterally), longissimus (located intermedially), and spinalis (located medially). The muscles of the erector spinae are used to maintain posture and help us stand erect. 14. The external intercostal muscles elevate the ribs during inspiration. The internal intercostals depress the ribs, but only during a forced expiration; a normal exhalation takes no active muscular effort. 15. Contraction of the diaphragm moves the entire muscle inferiorly, which expands the thoracic cavity, thus decreasing pressure in the thoracic cavity and increasing pressure in abdominopelvic cavity. 16. All four abdominal muscles compress the abdominal wall. The rectus abdominis flexes the vertebral column. The external and internal obliques and the transverse abdominis muscles produce lateral flexion when contracted unilaterally, or contribute to flexion of the vertebral column when both sides contract simultaneously. The oblique muscles are also capable of rotating the vertebral column. 17. The pelvic floor muscles form the pelvic diaphragm across the pelvic outlet, and support the viscera of the pelvic cavity. 18. The levator scapulae elevates and rotates the scapula inferiorly. The rhomboid major and minor elevates, adducts, and rotates the scapula inferiorly. The trapezius may elevate, depress, retract, or rotate the scapula superiorly. 19. In general, all posterior thoracic muscles either adduct or extend the arm at the shoulder.

20. The subscapularis rotates the arm medially, the supraspinatus abducts the arm, the infraspinatus adducts and rotates the arm laterally, and the teres minor muscle adducts and rotates the arm laterally. 21. The anterior compartment of the arm contains the three flexors of the elbow: the biceps brachii, brachialis, and brachioradialis muscles. Along with flexion at the elbow, the biceps brachii participates in flexion at the shoulder and supination of the elbow. The two pronators, pronator teres and pronator quadratus, are also located within the anterior compartment. 22. The pronator teres and pronator quadratus pronate the arm. Their antagonists, the biceps brachii and supinator muscles, supinate the arm. 23. Muscles in the anterior compartment of the forearm are all flexors of the wrist. 24. The abductor pollicis longus abducts the thumb, whereas the extensor pollicis longus and brevis extend the metacarpophalangeal joint of the thumb. 25. The abductor pollicis brevis abducts the thumb. The dorsal interossei muscle abducts fingers 2–5 because the abductor digiti minimi muscle abducts finger 5. 26. Thigh flexors are located within the anterior compartment of the thigh, adductors are located within the medial compartment, and abductors are located within the lateral compartment. There is also a posteriorly located gluteal group and hamstring group responsible for extension. 27. The biceps femoris, semitendinosus, and semimembranosus, collectively called the hamstring group, are the primary flexors of the leg. The sartorius, gracilis, and gastrocnemius muscles also facilitate in flexion of the leg. 28. The anterior compartment of the leg contains dorsiflexors of the foot and extensors of the toes. The lateral compartment contains evertors and plantar flexors of the foot. The posterior compartment of the leg contains plantar flexors and flexors of the leg and toes. 29. The extensor hallicus longus muscle extends the metacarpophalangeal joint of the great toe. The extensor digitorum brevis muscle extends both the metacarpophalangeal and proximal interphalangeal joints of toes 2–5. The deeper lumbrical muscle extends the proximal and distal interphalangeal joints of toes 2–5.

Answers to “Do You Know the Basics?” 1. A Feedback: The agonist is the prime mover at a joint. A synergist muscle may contribute force to the movement or help stabilize the joint during the movement, but it is the agonist that generates the majority of the force. 2. A Feedback: Contraction of the sternocleidomastoid muscles in unison flexes the cervical vertebrae, which is flexion of the head at the neck. 3. C Feedback: The diaphragm depresses as it contracts, simultaneously increasing the volume of the thoracic cavity and decreasing the volume of the abdominal cavity. 4. B Feedback: The inferior oblique muscle both depresses and adducts the eye. 5. C Feedback: The spinalis group of muscles participates in flexion of the vertebral column. 6. B Feedback: The dorsal interossei muscles of the hand are capable of flexion of metacarpophalangeal joints 2–5, extension of the proximal and distal interphalangeal joints of fingers 2–5, or abducting fingers 2–5. 7. B Feedback: All of the muscles within the anterior compartment of the leg are capable of dorsiflexion of the foot. The extensor digitorum longus and extensor halluces longus also extend the toes.

8. D Feedback: The brachialis, biceps brachii, and brachioradialis muscles all flex the arm at the elbow. The anconeus muscle is located within the posterior compartment of the arm and participates in extension. 9. C Feedback: The muscles of the hamstring group—the semitendinosus, semimembranosus, and biceps femoris—all originate at the ischial tuberosity and can extend the thigh at the hip, or flex the leg at the knee. 10. B Feedback: The gastrocnemius, located within the posterior compartment of the leg, is a primary mover for plantar flexion of the foot. 11. Muscles can be named according to (1) orientation of muscle fibers, (2) muscle attachments, (3) specific body regions, (4) muscle shape, (5) muscle size, (6) muscle heads/tendons of origin, (7) muscle function/movement, and (8) muscle position at body surface. 12. Closing of the eyes is accomplished by the orbicularis oculi muscle. Smiling requires contraction of the levator anguli oris, zygomaticus major, and zygomaticus minor to elevate the corners of the mouth. The risorius also contracts when you make a closedmouth smile. Closing or pursing of the lips is performed by the orbicularis oris, whereas closing the mouth is accomplished by the masseter and temporalis muscles, which elevate the mandible. 13. The suprahyoid muscles are located superior to the hyoid bone, and the infrahyoid muscles are located inferior to the hyoid bone. The suprahyoid muscles are associated with the floor of the mouth. In general, these muscles elevate the hyoid bone during swallowing and speaking. Contraction of the infrahyoid muscles will either depress the hyoid bone or depress the thyroid cartilage of the larynx. 14. The external and internal oblique muscles laterally flex the vertebral column (bend the body laterally) and rotate the vertebral column to the opposite side, if they contract unilaterally. If these muscles bilaterally contract, they compress the abdominal wall and flex the vertebral column. 15. Movements possible at the glenohumeral joint are (1) abduction by the deltoid muscle, (2) adduction by the latissimus dorsi and pectoralis major, (3) extension by the latissismus dorsi and deltoid, (4) flexion by the pectoralis major and deltoid, (5) lateral rotation by the infraspinatus and teres minor, and (6) medial rotation by the subscapularis. 16. The anterior compartment of the brachium primarily contains elbow flexors: the biceps brachii, brachialis, and brachioradialis. The posterior compartment contains extensors of the elbow: the triceps brachii and the anconeus. Because the biceps and triceps brachii also have attachments on the scapula, they also participate in extension and flexion, respectively, of the glenohumeral joint. 17. The flexor digitorum profundus lies deep to the flexor digitorum superficialis. Both muscles insert by way of four separate tendons into phalanges 2–5. The tendons of flexor digitorum profundus insert at the distal phalanges of digits 2–5, whereas the tendons of flexor digitorum superficialis only insert at the middle phalanges. Therefore, although both muscles are capable of flexing the wrist, the metacarpophalangeal joints, and the proximal interphalangeal joints, only the flexor digitorum profundus is capable of flexing the distal interphalangeal joints of digits 2–5. 18. The gluteus maximus is the primary mover for extension at the hip. The adductor magnus, biceps femoris, semitendinosus, and semimembranosus muscles act as synergists. 19. Balancing on the toes involves plantar flexion of the foot, which is accomplished primarily by the gastrocnemius and soleus muscles. 20. Inversion of the foot is accomplished by the tibialis anterior and tibialis posterior muscles.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: The orbicularis oculi muscle is responsible for closing of the eye, such as blinking or squinting. 2. C Feedback: The medial rectus muscle adducts the eye.

3. D Feedback: The extensors of the forearm are located in the posterior compartment of the brachium. The flexors are located in the anterior compartment. 4. A Feedback: The four heads of the quadriceps femoris muscle are located within the anterior compartment of the thigh. They are the primary movers for extension at the knee. 5. C Feedback: The fibularis tertius, longus, and brevis muscles originate at the fibula. All three are involved in eversion of the foot.

Answers to “Can You Synthesize What You’ve Learned?” 1. The inguinal region is one of the weakest areas of the abdominal wall. Within this region is the inguinal canal that allows the passage of the spermatic cord into the testis. This is the most common site of a rupture or separation of the abdominal wall in males. It is possible for rising pressure in the abdominal cavity, as might develop while straining to lift a heavy object, to push a segment of the small intestine into the canal causing a hernia. Since exercise can increase abdominal muscle tone, it can also help prevent an inguinal hernia. 2. The external urethral sphincter is located amongst the muscles of the pelvic floor. These muscles may have been damaged upon impact, which may have caused her to have difficulty controlling the release of urine from the bladder. 3. Exercises that involve flexion of the elbow, such as biceps curls, would help to strengthen the biceps brachii, brachialis, and brachioradialis muscles. Extension exercises such as bench dips or close-grip bench presses would help to strengthen the triceps brachii as well as the anconeus muscles. Pronation/supination exercise such as pronating and supinating the arm while holding a weight, with the elbow held at a 90 degree angle, would help strengthen the pronator teres and pronator quadratus, as well as the supinator muscles. 4. Flexion of the elbow when the arm is prone decreases the contribution of the brachioradialis muscle to the force of contraction, thereby relying primarily on the brachialis and biceps brachii.

Chapter 12 Answers to “What Did You Learn?” 1. Receptors monitor changes in both the internal and external environment of the body. Effectors include all three types of muscle tissue and glands. 2. The nervous system can be subdivided functionally into the sensory and motor subdivisions. The sensory subdivision is responsible for receiving sensory information from receptors. The motor subdivision is responsible for stimulating effector organs such as muscles or glands. 3. Excitability implies that a neuron is responsive to stimulation. Conduction refers to a neuron's ability to propagate electrical charge differences along its plasma membrane. Secretion describes the neuron's ability to release neurotransmitters in response to conductivity changes. 4. Dendrites are relatively short projections off of the cell body that direct electrical signals toward the cell body. An axon is a relatively longer projection that conducts the impulses away from the body. Synaptic vesicles contain neurotransmitters within synaptic bulbs, distal to the axon. Neurofibrils are aggregated bundles of intermediate filaments which provide tensile strength within the neuron. 5. Anterograde transport is the movement of materials from the cell body to synaptic knobs, and retrograde transport is the movement of materials from synaptic knobs to the cell body. Fast axonal transport is both anterograde and retrograde; it can move in either direction. Vesicles required at the distal end of the neuron are moved by anterograde transport, whereas waste products and potentially harmful products are moved by retrograde mechanisms back to the cell body. 6. The four structural types of neurons are classified based on the number of processes emanating directly from the cell body: Multipolar neurons have one axon and multiple dendrites, whereas bipolar neurons have one axon and only one dendrite. A unipolar neuron consists of only one axon that branches into two distinct ends. Anaxonic neurons possess only dendrites and no axon. 7. Interneurons are located entirely within the central nervous system. They receive stimulation from many other neurons and carry out the integrative function of the nervous system. In other words, they are responsible of processing information within the CNS. 8. Individual axons in the PNS are surrounded by neurolemmocytes and then wrapped in a delicate layer of loose connective tissue called the endoneurium. Groups of axons are wrapped into bundles, called nerve fascicles, by a cellular dense irregular connective tissue layer called the perineurium. All of the fascicles are bundled together by a superficial dense irregular connective tissue covering termed the epineurium. 9. A synapse is the specific location where a neuron is functionally connected to either another neuron or an effector. Most synapses within the nervous system are chemical synapses. Transmission at a chemical synapse occurs when neurotransmitter molecules stored in synaptic vesicles are released from the synaptic knob of a presynaptic neuron into the synaptic cleft. Some of the neurotransmitter diffuses across the cleft to bind to receptors within the postsynaptic plasma membrane to initiate another electrical signal. 10. Glial cells are significantly more numerous than neurons in the central nervous system. They also have higher metabolic and mitotic rates. This leaves them far more susceptible to free radical stress, DNA damage, and possibly unrestricted growth. Therefore, they are more likely to be the source of a brain tumor than neurons. 11. Microglial cells replicate in response to an infection within the brain. 12. Neurolemmocytes form myelin sheaths around axons in the peripheral nervous system. 13. Neurolemmocytes form myelin sheaths around axons in the peripheral nervous system, thereby increasing the velocity at which action potentials are propagated along the membrane of the neuron. Within the peripheral nervous system the process of myelination begins with a neurolemmocyte wrapping around a portion of the axon of a neuron. Multiple layers of myelination are formed as the neurolemmocyte wraps itself in consecutive layers around the axon. The plasma membranes of these multiple layers form the myelin sheath associated with myelinated neurons. 14. The success of PNS axon regeneration depends upon two primary factors: (1) the amount of damage, and (2) the distance between the site of the damaged axon and the structure it innervates. 15. A nerve cell may repair itself through a process called Wallerian degeneration. After an axon in the PNS is severed, the proximal portion of the severed end seals and begins to swell. The distal severed region degenerates and is phagocytized. The

neurolemmocytes in the distal region survive and together with the remaining endoneurium form a regeneration tube. The axon regenerates and remyelination occurs. The regeneration tube guides the axon sprout as it grows under the influence of nerve growth factor released by the neurolemmocytes. Innervation is restored as the growing axon contacts the original effector. 16. Both types of channels are normally closed. Chemically gated channels open in response to binding of a neurotransmitter. Voltage-gated channels open in response to changes in electrical charge (potential) across the plasma membrane. 17. The receptive segment of a neuron (dendrites and cell body), and the initial segment (the axon hillock), contain chemically gated ion channels. The conductive segment (axon and telodendria) and transmissive segment (synaptic knobs) contain only voltage-gated ion channels. 18. An electrical gradient is a difference in electrical charge between two areas. A chemical gradient reflects an unequal distribution of a substance between two areas. 19. Usually, the inside of the plasma membrane of a cell is relatively negative, and the outside is relatively positive. This difference of charge across the membrane is called the membrane potential. 20. Voltage is a measure of the amount of difference in charge across the phospholipid bilayer. The extent of the movement of ions (charged particles) across the bilayer is called current. Resistance is the sum of the forces that oppose current. Within a neuron, the integrity of the plasma membrane provides the resistance. Opening or closing of channels within the membrane can therefore change resistance and permit current, which is the flow of ions through the membrane. 21. The Na+/K+ pumps reestablish the gradients of both K+ and Na+ after an action potential. 22. Depolarization occurs in neurons when gated channels open, allowing positively charged Na+ to move into the cell, causing the inside of the neuron to become less negative. Hyperpolarization results through either the opening of gated K+ channels, that allow positively charged K+ to move out of the neuron, or the opening of gated Cl– channels, permitting negatively charged Cl– to move into the cell. Either the loss of a positively charged ion (K+) or the gain of a negatively charged ion (Cl–) causes the inside of the neuron to become more negative. 23. A graded potential occurs within the receptive segment of a neuron in response to opening of chemically gated channels. Action potential is generated at the initial segment of a neuron and is propagated along the axon, through the opening of voltage-gated channels. 24. An excitatory postsynaptic potential decreases the voltage across a membrane by allowing positively charged Na+ to enter the cell. An inhibitory postsynaptic potential hyperpolarizes the neuron by either allowing positively charged K+ to leave the cell or negatively charged Cl– to enter the cell. 25. The threshold membrane potential is the voltage difference that must be achieved in order to generate an action potential within the initial segment of a neuron. Typically this is at −55 mV, +15 mV above the resting membrane potential. If the ratio of IPSPs and EPSPs reaches the threshold membrane potential, only then will an action potential be generated and propagated along the neuron. 26. Depolarization occurs when the threshold voltage of −55 mV is reached; voltage-gated Na+ channels open and Na+ rapidly enters the cell, reversing the polarity from negative to positive. Repolarization occurs due to closure of the voltage-gated Na+ channels and opening of voltage-gated K+ channels. K+ moves out of the cell and polarity is reversed from positive to negative. 27. Depolarization resulting from the arrival of the action potential at the synaptic bulb triggers the opening of voltage-gated Ca2+ channels. Calcium enters the bulb and binds to receptors on the surface of vesicles containing neurotransmitters, signaling the vesicles to fuse with the plasma membrane, releasing their contents into the synaptic cleft. 28. Conduction along a myelinated neuron (saltatory conduction) is significantly faster than in an unmyelinated neuron because an action potential is generated only in unmyelinated nodes. 29. Group A fibers have conduction velocities that may be as fast as 150 meters per second; these fibers have both a large diameter and are myelinated. Most somatic sensory neurons that extend from receptors to the CNS, and all somatic motor neurons that extend from the CNS to skeletal muscles, are included in this group. 30. Neurotransmitters can be amino acids (glutamine, glycine, or aspartate), monoamines (epinephrine, norepinephrine, or dopamine), neuropeptides (enkephalins or somatostatin), or acetylcholine.

31. Neuromodulators are not neurotransmitters; however, they do regulate or alter the response of neurons to neurotransmitters. Thus, neuromodulators participate in the processing that occurs during the transmission of information. 32. In a converging circuit, a single postsynaptic neuron receives input from several presynaptic neurons. 33. Reverberating circuits utilize feedback to produce a repeated, cyclical stimulation of the same circuit. In a parallel after-discharge circuit, several neurons or neuronal pools process the same information at one time. A single presynaptic neuron stimulates different groups of neurons, each of which passes the nerve impulse along a pathway that ultimately synapses with a common postsynaptic cell.

Answers to “Do You Know the Basics?” 1. A Feedback: Neurotransmitters are released from the synaptic bulbs, distal to both the cell body and the axon. 2. B Feedback: Bipolar neurons have one axon and only one dendrite attached to the cell body. 3. D Feedback: Interneurons form circuits for integration and processing of stimuli, only within the central nervous system. 4. B Feedback: As Na+ enters a cell, down its concentration gradient, it causes a slight depolarization, which is the excitatory postsynaptic potential. 5. C Feedback: Mature ependymal cells are located within the lining of ventricles in the CNS. They contain small tufts of cilia, and participate in the production of cerebrospinal fluid in the choroid plexus. 6. D Feedback: Neurolemmocytes are responsible for myelination of neurons in the peripheral nervous system. 7. B Feedback: Voltage-gated Na+channels open at −55 mV, which is the threshold of an action potential. 8. C Feedback: Reverberating circuits utilize feedback to produce a repeated, cyclical stimulation of the same circuit. 9. B Feedback: An electrical synapse is composed of a presynaptic neuron and a postsynaptic neuron physically bound together. Gap junctions are present in the plasma membranes of both neurons and facilitate the flow of ions between the cells. 10. A Feedback: Myelination significantly increases the velocity of conduction along a neuron. 11. Structurally, neurons are classified based on the number of processes emanating directly from the cell body: Multipolar neurons have one axon and multiple dendrites, whereas bipolar neurons have one axon and only one dendrite. A unipolar neuron consists of only one axon that branches into two distinct ends. Anaxonic neurons possess only dendrites and no axon. Most sensory neurons are unipolar, with a few exceptions that are bipolar, located within olfactory mucosa of the nose and retina of the eye. In contrast, all motor neurons and most interneurons are multipolar. 12. Within the central nervous system, astrocytes carry out numerous important functions including formation of the blood-brain barrier, structural support, maintaining fluid composition, and assisting with the development of neurons. Ependymal cells assist with the production and circulation of the cerebrospinal fluid, microglial cells fight infection, and oligodendrocytes provide myelination. Within the peripheral nervous system, neurolemmocytes provide myelination and satellite cells protect and support cell bodies within ganglia. 13. Myelination is completed by neurolemmocytes in the PNS and by oligodendrocytes in the CNS. A neurolemmocyte can myelinate only a single portion of one axon in the PNS, whereas an oligodendrocyte can myelinate numerous axons at the same time within the CNS.

14. A nerve cell may repair itself through a process called Wallerian degeneration. After an axon in the PNS is severed, the proximal portion of the severed end seals and begins to swell. The distal severed region degenerates and is phagocytized. The neurolemmocytes in the distal region survive and together with the remaining endoneurium form a regeneration tube. The axon regenerates and remyelination occurs. The regeneration tube guides the axon sprout as it grows under the influence of nerve growth factor released by the neurolemmocytes. Innervation is restored as the growing axon contacts the original effector. 15. The resting membrane potential is established primarily through the efflux of K+ through leak channels. This movement follows the concentration gradient K+ out of the cell, but is in part opposed by the negative charge outside of the cell. Conversely, sodium ions diffuse into the neuron through leak channels, down their concentration gradient. The plasma membrane of the neuron is far more permeable to K+ than Na+. Therefore, a net decrease in positive charge occurs within the cell. At the same time, electrogenic Na+/K+ pumps move three sodium ions out of the cell for every two potassium ions that they bring in, also contributing to the difference of charge across the membrane. 16. A graded potential occurs locally within the receptive segment of a neuron in response to opening of chemically gated channels. Action potential is generated at the initial segment of a neuron and is propagated along the axon, through the opening of voltage-gated channels. Graded potentials may occur due to an influx of either positive or negative ions, and their strength is directly proportional to the amount of ions that enter the cell. On the other hand, action potentials are elicited only through the influx of positive ions, and can only occur once a minimal threshold voltage has been reached. 17. An excitatory postsynaptic potential decreases the voltage across a membrane by allowing positively charged Na+ to enter the cell. An inhibitory postsynaptic potential hyperpolarizes the neuron by either allowing positively charged K+ to leave the cell or negatively charged Cl– to enter the cell. If the ratio of IPSPs and EPSPs reaches the threshold membrane potential, only then will an action potential be generated and propagated along the neuron. 18.

19. Depolarization resulting as the arrival of the action potential at the synaptic bulb triggers the opening of voltage-gated Ca2+ channels. Calcium enters the bulb and binds to receptors on the surface of vesicles containing neurotransmitters, signaling the vesicles to fuse with the plasma membrane, releasing their contents into the synaptic cleft. 20. Neurotransmitters can be individual amino acids (glutamine, glycine, or aspartate), monoamines (epinephrine, norepinephrine, or dopamine), short polypeptides called neuropeptides (enkephalins or somatostatin), or acetylcholine which consists of an acetate molecule attached to a choline moiety.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Fast axonal transport is a form of retrograde movement from the synaptic knob to the cell body.

2. C Feedback: Astrocytoma is the most common type of tumor, affecting astrocytes in the brain. 3. C Feedback: Extracellular calcium is required to signal vesicles containing neurotransmitter in the synaptic bulb to fuse with the plasma membrane, releasing neurotransmitter into the synaptic bulb. 4. A Feedback: The receptive segment contains voltage-gated channels that respond to the presence of neurotransmitter in the synaptic cleft. Preventing the reuptake of serotonin will increase the duration of the graded potential that the neurotransmitter is able to generate in the postsynaptic neuron. 5. A Feedback: A reverberating circuit is associated with repetitive processing.

Answers to “Can You Synthesize What You’ve Learned?” 1. As the immune system destroys neurolemmocytes in the peripheral nervous system, saltatory conduction is prevented, and velocities of conduction in motor and/or sensory neurons are greatly diminished, possibly affecting vision and motor control. 2. Repair of damaged neurons is possible only if the amount of damage or the distance of the damage to the target is minimal. Regeneration requires formation of a regeneration tube from the remnants of the neurilemma and endoneurium of the original neuron. Growth of the new axon within the tube then occurs at approximately 2–5 mm per day. 3. Depolarization of the axon requires the opening of voltage-gated sodium channels. Neurotoxins that affect the opening of these channels would inhibit depolarization, and subsequently the action potential, along the axon.

Chapter 13 Answers to “What Did You Learn?” 1. The brain is composed of four major regions: the cerebrum, diencephalon, brainstem, and cerebellum. 2. A neural groove is formed as the cells on the periphery of the neural plate divide and produce neural crests. As the crests continue to expand, they merge, surrounding the neural groove, which now becomes the neural tube. 3. The five secondary brain vesicles are the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. In the adult brain, the telencephalon forms the cerebrum; the diencephalon forms the thalamus, hypothalamus, subthalamus, and epithalamus; the mesencephalon forms the rostral end of the brainstem; the metencephalon forms the pons and cerebellum; and the myelencephalon forms the medulla oblongata. 4. Gray matter of the cerebrum is located within the outer cerebral cortex, as well as within deeper cerebral nuclei. Within the spinal cord, gray matter is limited to one large central portion, surrounded by columns of white matter. 5. The dura mater is composed of two portions: the periosteal layer, lining superficial bones, and the deeper meningeal layer. Deep to the dura mater is the spacious arachnoid mater, and an even deeper pia mater covers the actual surface of the neural tissue. Cerebrospinal fluid is found within the subarachnoid space, in between the pia mater and dura mater. Although normally there is no spacing on either side of the dura mater, the epidural space is a potential cavity in between the meningeal and periosteal layers of the dura mater, and the subdural space may occur between the dura mater and arachnoid mater. 6. The falx cerebri is a large fold of dura mater located along the midsagittal plane within the longitudinal fissure, separating the left and right hemispheres of the brain. It is attached anteriorly to the crista galli and posteriorly to the internal occipital crest, stabilizing the brain within the cranium. 7. The fourth ventricle is located between the pons and cerebellum. It opens to the subarachnoid space via a single median aperture and paired lateral apertures. 8. The CSF provides the brain with buoyancy. Allowing the brain to float within a surrounding fluid distributes its weight within the cranium, protecting it from damage. CSF also provides a liquid cushion to protect delicate neural structures from sudden movements. Lastly, the CSF provides for environmental stability; it transports nutrients and chemical messengers to the brain, and removes waste products. 9. CSF is produced by the choroid plexus within the ventricles. It flows from the lateral ventricles and third ventricle into the cerebral aqueduct and then into the fourth ventricle. Additionally, a relatively small amount of CSF from the central canal of the spinal cord travels to the fourth ventricle as well. Most of the CSF in the fourth ventricle flows into the subarachnoid space by passing through openings in its membranous roof, either the paired lateral apertures or the single median aperture. CSF flows through the subarachnoid space surrounding the brain, spinal cord, and nerve fibers. As additional CSF is incorporated into the subarachnoid space, one-way flaps in the arachnoid villi open into the dural venous sinuses, allowing excess CSF to be released into the venous bloodstream. These flaps allow the CSF to be released into the blood, without allowing any venous blood to enter the subarachnoid space. 10. The blood-brain barrier strictly regulates which substances can and cannot enter the interstitial fluid of the brain from capillaries. 11. In most people, the left hemisphere is called the categorical hemisphere. It is specialized for language, and performing sequential or analytical reasoning. The opposite hemisphere then takes on the role of representational functions such as visiospatial relationships and analyses. 12. The corpus callosum provides the main method of communication between the hemispheres of the brain. 13. The five lobes are the frontal lobe, parietal lobe, temporal lobe, occipital lobe, and insula. The frontal lobe is primarily concerned with voluntary motor functions, concentration, verbal communication, decision making, planning, and personality. The parietal lobe is concerned with sensory reception as well as understanding speech and formulating words. The temporal lobe is involved with hearing, interpreting speech and language, and smell. The occipital lobe receives and processes incoming visual information and compares it to past visual experiences. The insula is involved in memory and the interpretation of taste. 14. The primary motor cortex is responsible for the control of voluntary skeletal muscle activity, and is located within the precentral gyrus of the frontal lobe. The motor speech area regulates patterns of breathing and controls the muscular movements necessary for

vocalization. It is located within the lateral portion of the left frontal lobe. The frontal eye field is on the superior surface of the middle frontal gyrus, and regulates eye movements necessary for binocular vision. 15. The five association areas of the cerebrum are the premotor cortex, the somatosensory association area, the visual association area, the auditory association area, and the functional regions such as the Wernicke area and gnostic area. 16. Association areas process incoming data or outgoing motor commands, as well as integrate sensory information into memory. 17. Commissural tracts serve as connections between the two cerebral hemispheres. Association tracts connect various regions within the same hemisphere. Projection fibers connect the cerebral hemisphere with inferior brain regions and the spinal cord. 18. Higher-order centers in the cerebral hemispheres tend to have different but complementary functions. Cerebral lateralization refers to this specialization of the two cerebral hemispheres. 19. In most people, the left hemisphere is specialized for language abilities, and is important in performing sequential and analytical reasoning tasks, such as those required in science and mathematics. The right hemisphere is usually the seat of imagination and insight, musical and artistic skill, perception of patterns and spatial relationships, and comparison of sights, sounds, smells, and tastes. 20. Cerebral nuclei are paired irregular masses of gray matter deep within the central white matter in the basal region of the cerebral hemispheres inferior to the floor of the lateral ventricle. The nuclei include the caudate nucleus (produce a pattern and rhythm of arm and leg movements while walking); amygdala (behavioral activities, moods, expression of emotions); putamen (subconscious level of muscular movement control); globus pallidus (both excites and inhibits thalamus activities and adjusts muscle tone); and claustrum (subconscious processing of visual information). 21. The pineal gland is located in the posterior portion of the epithalamus, just superior to the corpora quadragemina. It releases the hormone melatonin and is responsible for setting circadian rhythms. 22. The thalamus is the gateway to the cerebrum. It not only routes sensory information to the correct region of the cortex, but it may also attenuate the signal, preventing the cortex from having to process extraneous signals. 23. The ventromedial nucleus of the hypothalamus monitors levels of nutrients such as glucose and amino acids in the blood and produces sensations of hunger, whereas the anterior nucleus monitors the osmolality of the blood and produces the sensation of thirst. 24. The substantia nigra produces the neurotransmitter dopamine, which affects brain processes to control movement, emotional response, and ability to experience pleasure and pain. Degeneration of neurons within the substantia nigra is part of the etiology of Parkinson’s disease. 25. The tectal plate contains paired sensory nuclei responsible for processing auditory stimuli (the inferior colliculi) and visual stimuli (the superior colliculi). 26. The pontine respiratory center is the autonomic respiratory center of the pons. It regulates skeletal muscles involved in respiration. 27. The pyramids are located on the superior, anterior surface of the medulla oblongata. They contain the corticospinal tracts of motor projection fibers, which decussate within the pyramids to provide for contralateral communication from the cerebrum to skeletal muscles. 28. Three important autonomic centers are located in the medulla oblongata: The cardiac center regulates heart rate and strength of contraction of the heart, the vasoconstriction center regulates the diameter of blood vessels and subsequently blood pressure, and the medullary respiratory center sets the basal respiratory rate. 29. The cerebellum consists of two discrete hemispheres. Each hemisphere is separated into anterior and posterior lobes by the primary fissure. The cerebellar cortex consists of folds called folia, which consist of a cerebellar cortex of gray matter, with tracts of white matter called the arbor vitae underneath. 30. The middle cerebellar peduncles connect the cerebellum to the pons.

31. The cerebellum integrates somatic motor output from the cerebrum with proprioception and other sensory stimuli, in order to coordinate and fine-tune skeletal muscle movements. It can also store memories of previously learned movement patterns. 32. The limbic system is composed of the cingulate gyrus, parahippocampal gyrus, hippocampus, amygdaloid body, olfactory bulbs and tracts and cortex, fornix, septal nuclei, mammillary bodies, and some thalamic nuclei. 33. The limbic system is composed of multiple cerebral and diencephalic structures that collectively process and experience emotions. The hippocampus and parahippocampal gyrus are involved in long-term memory formation, and the amygdaloid body is involved in emotions such as fear. The olfactory pathways, such as the olfactory bulb, tracts, and cortex, are also associated closely with emotions, and are therefore also considered part of the limbic system. 34. The reticular activating center is the sensory component of the reticular formation of the midbrain. It processes sensory information and adjusts the cerebral state of arousal. It is therefore associated with states of consciousness. 35. Some CNS axons remain unmyelinated and are not completely mature until the teenage years. Since a person’s ability to carry out higher-order mental functions is a direct result of the level of nervous system maturation, some forms of cortical processing are limited until after puberty. 36. The association areas of the cerebrum are responsible for cognition. For example, the frontal association area (prefrontal cortex) integrates information from the sensory, motor, and association areas to enable an individual to think, plan, and execute appropriate behavior. 37. Agnosia is an inability either to recognize or to understand the meaning of various stimuli. For example, a lesion in the temporal lobe may result in an inability to recognize or understand the meaning of sounds or words. 38. Study methods that involve multiple repetition and assessment of the knowledge are optimum for forming long-term memories. 39. The amygdaloid body and hippocampus are responsible for developing emotional states. The prefrontal cortex, however, may override the presentation of these emotions. 40. Wernicke area is responsible for recognition of written and spoken language. 41. The olfactory, optic, and vestibulocochlear nerves only carry sensory information.

Answers to “Do You Know the Basics?” 1. D Feedback: The hypoglossal nerve is responsible for movement of the tongue. 2. C Feedback: The cerebellum integrates sensory information with somatic motor commands from the cerebrum, adjusting the motor commands to fine-tune movement. 3. C Feedback: The auditory association cortex is not as strongly involved in formation of long-term memories as are emotional states, repetition, or the cerebral nuclei of the limbic system. 4. D Feedback: The hypothalamus controls the autonomic nervous system, oversees the functions of the endocrine system, regulates body temperature, controls emotional behavior, controls food intake, controls water intake, and regulates the sleep/wake rhythms. It is not involved in somatic motor function. 5. C Feedback: The choroid plexus produces cerebrospinal fluid. It does not process stimuli. 6. A Feedback: The pyramids are located on the posterior of the medulla oblongata. The tegmenta are located deep within the midbrain, and the inferior colliculi are located on the posterior of the midbrain. The cerebral peduncles are located on the anterior surface of the midbrain.

7. B Feedback: The parietal lobe is located posterior to the central sulcus, and superior to the lateral sulcus. 8. A Feedback: The precentral gyrus contains the primary motor cortex. 9. B Feedback: Cerebral nuclei are clusters of unmyelinated cells deep within the white matter of the cerebrum. 10. A Feedback: The pons contains pontine respiratory centers, responsible for adjusting the respiratory rate. 11. The five secondary brain vesicles are the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. In the adult brain, the telencephalon forms the cerebrum; the diencephalon forms the thalamus, hypothalamus, subthalamus, and epithalamus; the mesencephalon forms the rostral end of the brainstem; the metencephalon forms the pons and cerebellum; and the myelencephalon forms the medulla oblongata. 12. CSF is produced by the choroid plexus within the ventricles. It flows from the lateral ventricles and third ventricle into the cerebral aqueduct and then into the fourth ventricle. Additionally, a relatively small amount of CSF from the central canal of the spinal cord travels to the fourth ventricle as well. Most of the CSF in the fourth ventricle flows into the subarachnoid space by passing through openings in its membranous roof, either the paired lateral apertures or the single median aperture. CSF flows through the subarachnoid space surrounding the brain spinal cord and nerve fibers. As additional CSF is incorporated into the subarachnoid space, one-way flaps in the arachnoid villi open into the dural venous sinuses, allowing excess CSF to be released into the venous bloodstream. These flaps allow the CSF to be released into the blood, without allowing any venous blood to enter the subarachnoid space. 13. The primary somatosensory association area interprets information received by the primary somatosensory cortex. 14. The visual association area processes information by analyzing movement, color, and form in order to identify what is seen. 15. Both the cerebellum and the cerebral nuclei participate in subconscious control of somatic motor movements. The cerebral nuclei, in general, remove unwanted movement from somatic motor commands, and the cerebellum integrates the motor commands with proprioception and other sensory stimuli. 16. The hypothalamus controls the autonomic nervous system, oversees the functions of the endocrine system, regulates body temperature, controls emotional behavior, controls food intake, controls water intake, and regulates the sleep/wake rhythms. It is not involved in somatic motor function. 17. The patient likely incurred injury to the hypothalamus. Along with regulating perception of thirst, and thereby regulating water intake, the hypothalamus is also considered as part of the limbic system, because of its role in the regulation of emotional states. 18. Stimuli resulting from pressure on the hand will enter the spinal cord where they will decussate and travel toward the brainstem, through projection tracts of white matter. In route through the medulla oblongata, the stimuli will trigger neurons in the inferior olivary nucleus, which will communicate the stimulus to the cerebellum. Continuing on through the pons, the stimulus will reach the ventral posterior nucleus of the thalamus, from where it will be routed to the primary somatosensory cortex of the left parietal lobe. 19. The limbic system is composed of the cingulate gyrus, parahippocampal gyrus, hippocampus, amygdaloid body, olfactory bulbs and tracts and cortex, fornix, septal nuclei, mammillary bodies, and some thalamic nuclei. 20. The surgeon must cut through the skin, the external periosteum, occipital bone of the cranium, dura mater (first the periosteal layer and then the meningeal layer), the arachnoid, the pia mater, then a glial cell covering before reaching the cerebral cortex.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: The trigeminal nerve carries sensory information from the mandible and maxilla. 2. D Feedback: The trigeminal nerve also innervates the lips.

3. A Feedback: The epidural space is located between the periosteal layer of the dura mater and the skull. 4. A Feedback: The left precentral gyrus contains the primary motor cortex responsible for movement of the right arm. 5. D Feedback: The abducens nerve innervates the lateral rectus muscle which turns the eye laterally.

Answers to “Can You Synthesize What You’ve Learned?” 1. Loss of somatic motor function may be caused by damage to the primary motor cortex along the precental gyrus of the frontal lobe. The slurred speech may indicate that the affected area also encompasses a portion anterior to the precentral gyrus, possibly including Broca area. Because of contralateral processing, loss of function on the right side of the body would indicate that the affected area is in the left hemisphere of the brain. 2. The blood-brain barrier would prevent the supplemented dopamine from entering the nervous system. Nervous tissue is isolated from the general circulation by the blood-brain barrier, which strictly regulates which substances can enter the brain. The advantage of the blood-brain barrier is that it helps prevent exposure of neurons in the brain to drugs, waste products in the blood, and variations in levels of normal substances such as hormones. 3. Dustin is more likely to survive damage to the cerebrum than the medulla oblongata. The cerebral cortex manages memories as well as somatic sensory and motor processing, some of which, although important, are not deadly if damaged. The medulla oblongata, however, controls multiple autonomic functions necessary for maintaining homeostasis, which cannot be interrupted.

Chapter 14 Answers to “What Did You Learn?” 1. There are 31 pairs of spinal nerves: 8 cervical (C1–C8), 12 thoracic (T1–T12), 5 lumbar (L1–L5), 5 sacral (S1–S5), and 1 coccygeal (Co) nerve. 2. The cervical enlargement contains the motor neurons that innervate the upper limbs. The lumbosacral enlargement contains the motor neurons that innervate the lower limbs. 3. The epidural space lies between the dura mater and the inner walls of the vertebrae. The subdural space is a potential space between the dura mater and arachnoid mater. The subarachnoid space lies between the arachnoid mater and pia mater, and contains the cerebrospinal fluid. 4. The anterior horn of gray matter contains the cell bodies of somatic motor neurons, whereas the lateral horn houses cell bodies of autonomic motor neurons. The posterior horn contains axons of sensory neurons as well as interneurons. 5. The anterior, posterior, and lateral funiculi are columns of white matter located on the respective sides of the gray matter of the spinal cord. Each folliculus contains tracts of ascending and descending association fibers. 6. Most neural pathways decussate to provide for contralateral processing. All neural pathways have a complimentary tract on the opposite side of the CNS. Most pathways are composed of two or more neurons. 7. Primary neurons compose part of the sensory receptor that detects a particular stimulus. Secondary neurons are located within the posterior horn of the spinal cord or brainstem, and conduct the stimulus to the thalamus. Tertiary neurons are also interneurons; they are also located within the hypothalamus, and conduct the stimulus to the primary somatosensory cortex. 8. The posterior funiculus-medial lemniscal pathway conducts sensory information about limb position, fine touch, precise pressure, and vibration. 9. Upper motor neurons originate in the cerebral cortex or the brainstem, and synapse with lower neurons in the brainstem or spinal cord. The lower neurons then conduct the commands out of the CNS. The upper motor neurons may be either stimulatory or inhibitory, whereas the lower neurons are only excitatory. 10. The corticobulbar and corticospinal tracts form direct pathways for somatic motor commands from the primary motor cortex to either the cranial or spinal nerves. Indirect pathways originate in the brainstem and conduct subconscious or reflexive motor commands. 11. A spinal nerve is composed of thousands of motor and sensory axons and is enveloped in the three successive connective tissue wrappings: endoneurium covering individual neurons, perineurium covering fascicles of neurons, and epineurium covering the entire nerve. 12. Spinal nerves are named after the vertebrae forming the inferior portion of the intervertebral canal through which they pass. For example, the nerve passing in between vertebrae C2 and C3 would be C3, the third cervical spinal nerve. The nerve exiting the spinal cord in between C7 and T1 is an exception, as it is called C8. 13. The posterior ramus of a spinal nerve is usually smaller than the anterior ramus and innervates the muscles of the posterior trunk. The anterior ramus splits into multiple other branches, innervating numerous structures, and in some cases forming nerve plexuses. 14. A dermatome is a specific section of skin innervated by a specific spinal nerve. Loss of sensation in a dermatome may indicate damage to its specific spinal nerve. 15. A typical nerve plexus consists of a network of interwoven anterior rami from several spinal nerves. The neurons from one ramus may contribute to multiple nerves, and a single named nerve may consist of neurons originating at numerous levels along the spinal cord. 16. Intercostal nerves, primarily, innervate intercostal muscles, as well as dermatomes of the thorax, axilla, and the medial aspect of the arm. 17. The phrenic nerve innervates the diaphragm.

18. The axillary nerve carries somatic motor commands to the deltoid muscle, as well as somatic sensory information from the superolateral aspect of the arm. 19. The radial nerve innervates the posterior muscles of the arm and forearm. It receives sensory nerve signals from the posterior arm and forearm surface and the dorsolateral side of the hand. The ulnar nerve innervates some of the anterior forearm muscles and most of the intrinsic hand muscles. It receives sensory nerve signals from the skin of the dorsal and palmar aspects of the pinky finger and the medial half of the ring finger. 20. The femoral nerve innervates the quadriceps femoris. Damage to the nerve may cause difficulty with extension at the knee. 21. The sacral plexus is formed from the anterior rami of L4–S4, and innervates the gluteal region, pelvis, perineum, posterior thigh, and almost all of the leg and foot. 22. All reflexes have four common properties: (1) A stimulus is required to initiate a response to sensory input; (2) a rapid response requires that few neurons are involved and synaptic delay is minimal; (3) a preprogrammed response occurs the same way every time; and (4) an involuntary response requires no conscious intent or preawareness of the reflex activity. 23. The five steps in a reflex arc are as follows: (1) A stimulus activates a receptor; (2) the nerve impulse travels through a sensory neuron to the spinal cord; (3) the nerve impulse is processed in the integration center by neurons; (4) a motor neuron transmits a nerve impulse to an effector; and (5) the effector responds to the nerve impulse from the motor neuron. 24. In a monosynaptic reflex, the sensory axons synapse directly on the motor neurons, whose axons then project to the effector. Interneurons do not function in this type of reflex. More complex neural pathways are observed in polysynaptic reflexes, which have a number of synapses involving interneurons within the reflex arc. 25. The four common spinal reflexes are the stretch reflex, Golgi tendon reflex, withdrawal reflex, and crossed-extensor reflex. 26. A hypoactive reflex may indicate damage to a segment of the spinal cord, or it may suggest muscle disease or damage to the neuromuscular junction. 27. The basal plates develop into the anterior and lateral horns, motor structures of the gray matter, and the anterior part of the gray commissure of the spinal cord. The alar plates develop into posterior horns, sensory structures of the gray matter, and the posterior part of the gray commissure.

Answers to “Do You Know the Basics?” 1. A Feedback: The arachnoid mater lies just deep to the subdural space. 2. D Feedback: The anterior root of a nerve contains only motor neurons. The posterior root contains only sensory neurons. 3. C Feedback: Tertiary neurons are interneurons; they are also located within the hypothalamus, and conduct the stimulus to the primary somatosensory cortex. Primary neurons compose part of the sensory receptor that detects a particular stimulus. Secondary neurons are located within the posterior horn of the spinal cord or brainstem, and conduct the stimulus to the thalamus. 4. B Feedback: The spinocerebellar tract carries sensory information to the cerebellum. 5. B Feedback: The radial, ulnar, axillary, median, and musculocutaneous nerves originate from the brachial plexus. 6. B Feedback: The posterior ramus provides innervation to the muscles of the back and dorsal dermatomes. 7. C Feedback: Intercostal nerves originate from between thoracic vertebrae, and innervate intercostal muscles, as well as dermatomes of the thorax, axilla, and the medial aspect of the arm.

8. A Feedback: The femoral nerve innervates the anterior of the thigh, whereas the sciatic nerve provides innervations to the posterior of the thigh. 9. D Feedback: A stretch reflex is a monosynaptic response to stretching of a muscle which adjusts muscle tone. 10. B Feedback: A hypoactive reflex may indicate damage to a segment of the spinal cord, or it may suggest muscle disease or damage to the neuromuscular junction. 11. The spinal nerves are named after the vertebrae forming the inferior portion of the intervertebral canal through which they pass. For example, the nerve passing in between vertebrae C2 and C3 would be C3, the third cervical spinal nerve. The nerve exiting the spinal cord in between C7 and T1 is an exception, as it is called C8. Nerves C1 through C8 originate at the cervical level of the spinal cord, T1 through T12 originate at the thoracic level, L1 through L5 originate at the lumbar level, S1 through S5 originate at the sacral level, and the coccygeal nerve originates at the coccygeal level of the spinal cord. 12. The anterior horn of gray matter contains the cell bodies of somatic motor neurons, whereas the lateral horn houses cell bodies of autonomic motor neurons. The posterior horn contains axons of sensory neurons as well as interneurons. 13. The posterior funiculus-medial lemniscal pathway conducts sensory information about limb position, fine touch, precise pressure, and vibration, through the posterior funiculi of the spinal cord. The anterolateral pathway conducts sensory information through the anterior and lateral funiculi about touch, pressure, pain, and temperature, to the primary somatosensory cortex. 14. Upper motor neurons originate in the cerebral cortex or the brainstem, and synapse with lower neurons in the brainstem or spinal cord. The lower neurons then conduct the commands out of the CNS. The upper motor neurons may be either stimulatory or inhibitory, whereas the lower neurons are only excitatory. 15. The axillary nerve innervates the deltoid and teres minor muscles, and the superolateral dermatome of the arm. The median nerve innervates most of the anterior muscles of the forearm, and the palmar aspects and dorsal tips of the lateral 3½ digits. The musculocutaneous nerve innervates the coracobrachialis, biceps brachii, and brachialis muscles, as well as dermatomes on the lateral region of the forearm. The radial nerve innervates the posterior arm and forearm muscles, and the brachioradialis muscle. It also innervates dermatomes in the posterior region of the arm and forearm, and the dorsal aspect of the lateral 3 digits, except their tips. The ulnar nerve innervates the anterior forearm muscles and the intrinsic hand muscles. The ulnar nerve also innervates dermatomes on the dorsal and palmar aspects of the medial 1½ digits. 16. The lumbar plexuses are formed from the anterior rami of spinal nerves L1–L4, and innervate muscles and dermatomes of the anterior and superomedial aspects of the thigh, lower anterior leg, and medial foot. 17. The tibial nerve innervates posterior thigh and leg muscles, and plantar foot muscles. The common fibular nerve innervates the short head of the biceps femoris. 18. The five steps in a reflex arc are (1) a stimulus activates a receptor; (2) the nerve impulse travels through a sensory neuron to the spinal cord; (3) the nerve impulse is processed in the integration center by neurons; (4) a motor neuron transmits a nerve impulse to an effector; and (5) the effector responds to the nerve impulse from the motor neuron. 19. A stretch reflex is a monosynaptic response that contracts a muscle in response to stretching or distention. A Golgi tendon reflex is a polysynaptic process that lengthens and/or relaxes muscles to prevent tensing or overcontracting. 20. The alar plates are located on the anterior aspect of the neural tube, whereas the basal plates are located on the posterior aspect. The basal plates develop into the anterior and lateral horns, motor structures of the gray matter, and the anterior part of the gray commissure of the spinal cord. The alar plates develop into posterior horns, sensory structures of the gray matter, and the posterior part of the gray commissure.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: The ulnar nerve descends along the medial side of the arm. It travels posterior to the medial epicondyle of the humerus and then runs along the ulnar side of the forearm.

2. C Feedback: The ulnar nerve innervates the anterior forearm muscles and the intrinsic hand muscles. 3. A Feedback: The ulnar nerve innervates the anterior forearm muscles and the intrinsic hand muscles, including the adductor pollicis. 4. A Feedback: The sacral plexus consists of anterior roots from spinal nerves L4–S4. A herniated disk in the lumbar region could put pressure on the roots contributing to the sciatic nerve which innervates the posterior aspect of the leg, thereby causing pain. 5. D Feedback: The superficial fibular nerve innervates the dorsal portion of the foot.

Answers to “Can You Synthesize What You’ve Learned?” 1. Arthur injured his spinal column at the cervical level. Although he may regain partial function of nerves originating at this level once the inflammation associated with the injury subsides, he is unlikely to regain complete function if the spinal cord was permanently injured. 2. The common fibular nerve may have been injured by the break of the fibula or because of too much pressure from the cast. The anterior and lateral leg muscles would have been paralyzed, leaving her unable to dorsiflex or evert the foot. 3. The piece of glass elicited a withdrawal reflex of her foot, which was accompanied by a cross-extensor reflex to help her maintain balance. The withdrawal reflex causes the one lower limb to flex at the knee, due to contraction of hamstring muscles. In contrast, the crossed-extensor reflex stimulates the quadriceps femoris muscle to contract on the other limb, so that it remains extended and supports her body weight.

Chapter 15 Answers to “What Did You Learn?” 1. The somatic nervous system carries stimuli that a person is consciously aware of, from or to the CNS. The somatic sensory portion includes detection of stimuli from the special senses, skin, and proprioceptors. The somatic motor portion involves the control of skeletal muscles by the CNS. The autonomic nervous system involves stimuli processed below the conscious level. The visceral sensory components include receptors that detect stimuli associated with blood vessels and internal organs or viscera. The autonomic motor components transmit nerve signals from the CNS to cardiac muscle, smooth muscle, and glands. 2. A single lower motor neuron extends from the CNS to skeletal muscle fibers in the somatic nervous system. In comparison, a chain of two lower motor neurons extends from the CNS to innervate cardiac muscle, smooth muscle, and glands in the ANS. Somatic motor neurons have large-diameter myelinated neurons that always release the neurotransmitter acetylcholine. Preganglionic autonomic motor neurons are also myelinated, but do not have a large diameter. The postganglionic neurons have axons with even smaller diameters, and are unmyelinated. 3. The parasympathetic division functions to conserve and replenish nutrients when at rest. 4. Sympathetic pathways have short, myelinated preganglionic fibers, with numerous branchings. Parasympathetic preganglionic fibers are also myelinated, but are relatively longer, with fewer branchings. Sympathetic postganglionic fibers are shorter and are unmyelinated, whereas parasympathetic postganglionic fibers are relatively longer and myelinated. Parasympathetic pathways originate at the brainstem and S2–S4 regions of the spinal cord. The sympathetic branches originate at the T1–L1 levels of the spinal cord. 5. The short preganglionic fibers of the sympathetic division, along with their extensive branching early in the pathway, facilitate the dispersal necessary for mass activation. 6. The occulomotor nerve (CN III) provides for autonomic motor functions of the eye such as the cilliary muscle and papillary constrictor muscles. The facial nerve (CN VII) innervates the lacrimal gland, as well as the sublingual and submandibular salivary glands, and several other small glands of the oral and nasal cavities. Branches off of the glossopharyngeal nerve (CN IX) innervate the parotid salivary gland. Lastly, the vagus nerve (CN X) innervates the viscera of the thoracic cavity (heart, lungs, and trachea), and the abdominal cavity (liver, gallbladder, stomach, spleen, pancreas, kidneys, ureters, small intestine, and the proximal portion of the large intestine). 7. The splanchnic nerves innervate organs of the pelvic cavity (distal colon, rectum, urinary bladder, gonads, and penis or vagina, and uterus). 8. Sympathetic trunk ganglia are part of the sympathetic trunks, which are located lateral to the vertebral column. Prevertebral ganglia are located anterior to the vertebral column and cluster around the origins of major abdominal organs. 9. White rami communicantes carry myelinated preganglionic axons to the sympathetic trunk. White rami communicantes are found only on the T1–L2 spinal nerves. In contrast, gray rami communicantes carry postganglionic axons and extend from the sympathetic trunk to all spinal nerves. 10. Splanchnic nerves are preganglionic axons that leave the sympathetic trunk ganglia without synapsing, and extend to prevertebral ganglia. Within the prevertebral ganglia, the preganglionic axon will synapse with a ganglionic neuron, and the postganglionic axon will travel to the effector organs. Most abdominal organs and some pelvic organs receive their sympathetic innervation via this pathway. 11. In a spinal nerve pathway, pre- and postsynaptic neurons synapse at a sympathetic trunk ganglion. Spinal nerve pathways innervate the skin of the neck, torso, and limbs. Preganglionic neurons of the splanchnic nerve pathway synapse at prevertebral ganglia, rather than at the sympathetic chain ganglia, and innervate viscera of the abdominal and pelvic cavities. 12. The adrenal medulla releases the neurotransmitter epinephrine and norepinephrine into the blood where they circulate as endocrine hormones and prolong the effects of sympathetic stimulation. 13. Cholinergic neurons include all sympathetic and parasympathetic preganglionic neurons, all parasympathetic ganglionic neurons, and specific sympathetic ganglionic neurons that innervate sweat glands of the skin and blood vessels in skeletal muscle tissue. All other sympathetic ganglionic neurons are adrenergic.

14. Nicotinic receptors are located on the cell bodies of ganglionic neurons and cells of the adrenal medulla. Muscarinic receptors are located on plasma membranes of target cells in the parasympathetic division as well as some sympathetic pathways, such as those that innervate sweat glands and blood vessels in the skeletal muscle. 15. Binding of neurotransmitters to nicotinic receptors opens sodium ion channels, allowing more positive ions to enter the cell, generating an excitatory postsynaptic potential. 16. Dopamine, epinephrine, and norepinepherine are catecholamines. 17. Activation of α1 adrenergic receptors stimulates smooth muscles, causing vasoconstriction. Stimulation of β2 adrenergic receptors causes relaxation of smooth muscle, causing vasodilation. 18. A decrease in stimulation below the sympathetic tone causes vessel dilation, whereas an increase above sympathetic tone causes vessel constriction. 19. Sympathetic stimulation increases heart rate, parasympathetic stimulation decreases heart rate. 20. The male penis becomes erect as a result of parasympathetic innervation, and ejaculation of semen from the penis occurs as a result of sympathetic innervations. 21. The smooth muscle of blood vessels, sweat glands, arrector pili muscles of the skin, and neurosecretory cells of the adrenal medulla are only stimulated by sympathetic pathways. 22. Autonomic plexuses are collections of sympathetic postganglionic axons and parasympathetic preganglionic axons, as well as some visceral sensory axons. 23. An increase in blood pressure stimulates baroreceptors in large blood vessels, which transmit the signal by visceral sensory fibers to the cardiac center of the medulla oblongata. The signals then interfere with sympathetic output, decreasing heart rate and consequently blood pressure. 24. The hypothalamus is the integration and command center for autonomic functions.

Answers to “Do You Know the Basics?” 1. C Feedback: Splanchnic nerves are preganglionic axons that leave the sympathetic trunk ganglia, without synapsing, and extend to prevertebral ganglia. 2. B Feedback: Parasympathetic pathways originate at the brainstem and S2–S4 regions of the spinal cord. 3. C Feedback: The parasympathetic division of the ANS increases gastric motility and digestion. 4. A Feedback: Autonomic tone is maintained by constant stimulation by the ANS. 5. D Feedback: White rami communicantes carry myelinated preganglionic axons to the sympathetic trunk. 6. C Feedback: Acetylcholine is released by all parasympathetic axons, all preganglionic sympathetic axons, and a few postganglionic sympathetic axons. 7. C Feedback: The hypogastric plexus innervates pelvic organs. 8. C Feedback: Sympathetic pathways have short, myleinated preganglionic fibers. Parasympathetic preganglionic fibers are also myelinated, but are relatively longer.

9. A Feedback: Nicotinic receptors are located on the cell bodies of ganglionic neurons and cells of the adrenal medulla. 10. D Feedback: β receptors are adrenergic and bind epinephrine or norepinepherine. β1 receptors are stimulatory, whereas β2 cells are inhibitory, and cause either vasodilation or vasoconstriction. 11. The four CNS regions that control the autonomic function are the hypothalamus, brainstem, spinal cord, and cerebrum. 12. The sympathetic trunk ganglia are immediately lateral to the vertebral column (on both sides) and are a part of the sympathetic trunks. The prevertebral ganglia are clusters of sympathetic division neuron cell bodies of ganglionic neurons located anterior to the vertebral column on the anterolateral wall of the abdominal aorta at the base of major abdominal arteries. The terminal ganglia are a collection of parasympathetic division neuron cell bodies of ganglionic neurons located very close to the target organ, while intramural ganglia contain parasympathetic ganglionic cell bodies within the wall of a target organ. 13. Sympathetic postganglionic fibers are relatively shorter, unmyelinated, and release the neurotransmitters epinephrine and norepinepherine. Parasympathetic postganglionic fibers are relatively longer, myelinated, and release acetylcholine. 14. The parasympathetic branch of the ANS stimulates gastric motility, secretion along the alimentary tract, salivary gland secretion, and glycogenesis in the liver. Conversely, the sympathetic branch decreases gastric motility, decreases secretions, and stimulates glycogenolysis from the liver. 15. Acetylcholine opens ion channels within nicotinic receptors, always generating EPSPs. Acetylcholine affects cells possessing muscarinic receptors through second messengers, either stimulating or at times inhibiting the target cells. 16. Cooperative effects are seen when both parasympathetic and sympathetic stimulation cause different effects that together produce a single, distinct result. Antagonistic interactions are seen when the two branches of the ANS have opposing effects on the same target. 17. The general functions of the sympathetic division are concerned with fight or flight, such as preparing the body for emergencies (e.g., increased blood pressure and rate of heart beat, increased release of stored nutrients, increased respiration rate, dilation of pupils). The parasympathetic division is primarily involved with maintaining the body’s internal environment (homeostasis) and has been nicknamed the “resting and digesting” system, because it concerns itself with those activities. 18. Mass activation of the sympathetic branch of the autonomic nervous system may cause a dangerous rise in blood pressure, possibly damaging blood vessels. 19. Upon filling, baroreceptors in the bladder wall are stretched and nerve signals are transmitted along sensory neurons to interneurons within the CNS. Nerve signals are then transmitted along motor neurons to stimulate the contraction of the urinary bladder. 20. A decrease in stimulation below the sympathetic tone causes vessel dilation, whereas an increase above sympathetic tone causes vessel constriction.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: A sympathetic response would stimulate vasodilation. 2. A Feedback: Release of epinephrine and norepinephrine from the adrenal medulla are part of the sympathetic response to possible danger. 3. A Feedback: A beta blocker would inhibit sympathetic stimulation to the heart, thus decreasing heart rate. 4. D Feedback: Albuterol would bind to β2 adrenergic receptors, causing a decrease in stimulation of smooth muscle.

5. C Feedback: Decreased parasympathetic stimulation would decrease secretion of HCl from gastric glands.

Answers to “Can You Synthesize What You’ve Learned?” 1. The sympathetic nervous system provides a capacity to quickly respond to a dangerous situation, quickly adjusting physiological functions. 2. Decreased blood flow to skeletal muscles may occur because the body is also routing increased blood flow to the digestive system. 3. The parasympathetic pathways activated, in response to the need for digestion, may also lower blood pressure and heart rate.

Chapter 16 Answers to “What Did You Learn?” 1. A sensation is our conscious awareness of incoming sensory information. A stimulus is a change in the environment that is detected by a receptor. Only a stimulus leading to an impulse that reaches the cerebral cortex results in a sensation. 2. Receptors possess channels that open in response to extracellular stimuli and generate an action potential, thereby transducing the stimulus into an action potential. 3. Tonic receptors respond continuously to stimuli at a constant rate. Phasic receptors detect a new stimulus or a change in a stimulus that has already been applied, but over time their sensitivity decreases. 4. Hearing is one of the special senses that utilize mechanoreceptors to detect external stimuli (externoceptors). Taste is also one of the special senses. It also utilizes chemoreceptors to detect external stimuli (externoceptors). Stretch receptors in the urinary bladder are baroreceptors that respond to internal stimuli (enteroceptors). 5. Free nerve endings are located in the papillary layer of the dermis. Root hair plexuses are located within the reticular layer of the dermis, and tactile disks are located within the stratum basale of the epidermis. 6. Pain associated with a myocardial infarction may be referred to the skin dermatomes innervated by the T1–T5 spinal nerves, which lie along the pectoral region and the medial side of the arm. 7. Odorant molecules must first dissolve in the mucus lining the olfactory mucosa, before binding to chemoreceptors. 8. Secondary neurons often transmit olfactory stimuli to the amygdala, which is involved in emotional states. 9. Taste buds are located on the foliate, vallate, and fungiform papillae. They consist of a bundle of gustatory cells clustered around a central pore and are surrounded by support cells. 10. Sweet tastes are generated by sugars, salty tastes are elicited by sodium or potassium ions, sour tastes are generated by acids, bitter tastes are primarily produced by alkaloids, and the umami taste is generated by amino acids such as aspartate and glutamate. 11. The conjunctiva coverts the external, anterior surface of the eye and the inside of the eyelid. It lubricates, nourishes, and protects the eye. 12. A lacrimal gland continuously produces lacrimal fluid (tears). Excretory ducts conduct the tears into the conjunctival sac of the superior eyelid. There, the blinking motion of the eyelids "washes" the tears over the eyes. The tears drain through the lacrimal puncta into the lacrimal canaliculi. A lacrimal sac temporarily stores the tears. The nasolacrimal duct receives the tears and delivers it into the nasal cavity. 13. The fibrous tunic, the external layer of the eye wall, is composed of the anterior cornea and the posterior sclera. The cornea refracts incoming light rays into the interior of the eye, while the sclera provides for eye shape and protects its delicate internal components. The vascular tunic, the middle layer of the eye wall, is composed of three distinct regions: the choroid, the ciliary body, and the iris (from posterior to the anterior). The choroid houses a vast network of capillaries that supply both nutrients and oxygen to the retina. The ciliary body is composed of four bands of smooth muscle organized into a ring and collectively called the ciliary muscle, which functions in lens shape change for near and far vision. The most anterior region of the middle layer of the eye is the iris. It is readily visible anteriorly with a central black hole, called the pupil. The iris is composed of two layers of pigment-forming cells (anterior and posterior layers), and two groups of smooth muscle fibers, whose contractions adjust the diameter of the pupil to regulate light entry. The internal tunic is called the retina. It is composed of an outer pigmented layer and an inner neural layer. The outer pigmented layer absorbs light rays that pass through the inner layer. The inner neural layer houses all of the photoreceptors and their associated neurons. This inner neural layer is responsible for receiving light rays and converting them into nerve impulses that are transmitted to the brain. 14. The ciliary muscles in the ciliary body contract to produce the tension in the suspensory ligaments. When the ciliary muscles relax, the ciliary body moves posteriorly, away from the lens, and so the tension on the suspensory ligaments increases. Constant tension applied to the suspensory ligaments causes the lens to flatten so that distant objects may be observed. The process of making the lens more spherical in order to view close-up objects is called accommodation. It is controlled by the parasympathetic division of the ANS. Stimulation of the ciliary muscle by parasympathetic axons causes the muscle to contract. When the ciliary muscle contracts, the entire ciliary body moves anteriorly and thus moves closer to the lens itself. This process allows for a reduction in the suspensory ligament tension and a release in some of their "pull" on the lens, so the lens can become more spherical.

15. The aqueous humor provides nutrients and oxygen to the lens and cornea, and helps maintain the chemical environment within the anterior cavity of the eye. The vitreous humor helps maintain eye shape, supports the retina to keep it flush against the back of the eye, and transmits light from the lens to the retina. 16. Both rods and cones contain an inner segment containing most of the cellular machinery, and an outer segment containing multiple photoreceptor-containing disks, which are embedded within the epithelium of the pigmented layer. Structurally, rods are narrower than cones and contain the photopigment rhodopsin, which is optimized for detecting low levels of light at a wavelength of approximately 500 nm. Thus, cones are specialized for vision with low light such as night vision. Cones contain one of either three photopigments called photopsins, which are specialized for transducing colors under bright light. 17. Dark adaptation occurs as rods are bleached from exposure to bright light, and require time to regenerate rhodopsin. Light adaptation is the converse, resulting from sudden exposure to bright light after a period of low light, at which point cones that have been bleached during exposure to light require time to regenerate photopsins. 18. In the absence of light, active cis-retinol stimulates the production of cGMP, which in turn maintains the dark current—a graded potential caused by the opening of ligand-gated sodium channels in response to cGMP. The graded potential causes the opening of voltage-gated calcium channels, resulting in the release of the neurotransmitter glutamate from the receptor cell. Glutamate causes an IPSP in the downstream bipolar cell, inhibiting it. Upon exposure to light, cis-retinol is converted to the trans isoform of the photopigment, decreasing the production of cGMP. A decrease in cGMP causes closing of sodium channels, loss of the graded potential, closing of calcium channels, and a subsequent inhibition of glutamate release. Without glutamate, the IPSP is no longer maintained in the bipolar cell, which depolarizes and subsequently stimulates ganglion cells, which conduct the action potential to the brain. 19. Axons from each cranial nerve cross over, thereby ensuring that each hemisphere of the brain receives visual information from both eyes. 20. A deer sacrifices depth perception for a wider field of vision. 21. The external acoustic meatus conducts sound waves to the tympanic membrane, while preventing entry of foreign objects. 22. Auditory ossicles are located in the middle ear, in between the tympanic membrane and the oval window. They amplify vibrations from the tympanic membrane as they transduce them to the inner ear. 23. Membranous labyrinths are membrane-lined, fluid-filled tubes and spaces within bone. The membranous labyrinth is housed within a cavernous space in dense bone, called the bony labyrinth, which is located within the petrous part of the temporal bone. The bony labyrinth consists of three regions: the cochlea, vestibule, and semicircular canals. The cochlear duct lines the cochlea, the utricle and saccule form the membranous labyrinth of the vestibule, and the semicircular ducts line the semicircular canals. 24. Steps for detecting sounds are as follows: (1) Sound waves are collected by the auricle and funneled through the external auditory canal to make the tympanic membrane vibrate. (2) The vibration of the tympanic membrane causes movement in the auditory ossicles. (3) The foot of the stapes vibrates moves like a piston in the oval window, causing pressure waves in the perilymph fluid of the inner ear. (4) Pressure waves travel through the perilymph in the scala vestibuli. (5) Pressure waves cause the vestibular membrane to vibrate, resulting in pressure wave formation in the endolymph of the cochlear duct. (6) Pressure waves in the cochlear duct displace a specific region of the basilar membrane causing distortion of stereocilia on hair cells of the spiral organ. This distortion causes a stimulus in the cochlear nerve. Remaining pressure waves are transferred to the perilymph of the scala tympani. 25. Frequency is the pitch of a sound, and corresponds to the number of waves that move past a point during a specific amount of time. Intensity refers to a sound’s loudness. Louder sounds increase the rate of nerve signals relayed to the brain. 26. Auditory stimuli from the cochlear nerve terminate in the cochlear nucleus of the brainstem. Secondary neurons then conduct the information simultaneously to the inferior colliculus of the midbrain and to the superior olivary nuclei of the pons. Immediately, output from the pons, back to the middle ear, adjusts tension of the stapedius and tensor tympani muscles, adjusting the intensity with which the ossicles vibrate. Within the inferior colliculus, startle reflexes may be initiated, prior to transmitting the nerve signals to the medial geniculate nucleus of the thalamus. After attenuation of the signal within the thalamus, tertiary neurons conduct the signal to the primary auditory cortex within the temporal lobe, where perception of sound occurs. 27. Tilting of the head causes the otolithic membrane to shift its position on the macula surface, thus distorting the stereocilia.

28. The utricle and saccule detect linear acceleration of the head and the position of the head relative to gravity during static equilibrium. When a linear force is applied upon the otolithic membrane, its position shifts, and a force is applied to the stereocilia, distorting them. Bending of the stereocilia results in a change in the amount of neurotransmitter released from the hair cells, and a simultaneous change occurs in the stimulation of the sensory neurons of the vestibular branch of the vestibulocochlear nerve. 29. The ampullae associated with the semicircular canals detect rotational acceleration. As the head accelerates, endolymph within the corresponding canal lags behind, putting pressure on the cupula. Bending of the cupula causes a deflection of stereocilia, which in turn results in a change in the amount of neurotransmitter released from the hair cells, and a simultaneous change occurs in the stimulation of the sensory neurons of the vestibular branch of the vestibulocochlear nerve.

Answers to “Do You Know the Basics?” 1. B Feedback: Free nerve endings are unencapsulated. Lamellated corpuscles, bulbous corpuscles, and end bulbs are all encapsulated. 2. D Feedback: Thermoreceptors detect changes in temperature. 3. C Feedback: The maculae are components of the vestibular apparatus, which detect linear acceleration and the position of the head. They are located within the utricle and saccule. 4. D Feedback: Accommodation in order to focus on a nearby object involves contraction of the ciliary body, changing the shape of the lens to better refract light. The shape of the pupil does not change to accommodate near vision. 5. B Feedback: The conjunctiva does not cover the cornea. 6. A Feedback: The outermost covering of the eye is the fibrous tunic. The deepest layer is the retina. 7. B Feedback: The external acoustic meatus directs sound waves through the outer ear to the tympanic membrane. 8. A Feedback: Olfaction is the only sense not integrated within the thalamus. 9. C Feedback: Lacrimal fluid moistens the surface of the eye; it does not humidify the entire orbit. 10. C Feedback: The cochlear duct contains stereocilia which transduce sound waves into action potential. 11. Chemoreceptors respond to the binding of ligands to receptors, and occur in taste buds and the olfactory mucosa of the nose. Thermoreceptors detect temperature changes, and are present in the skin and hypothalamus. Photoreceptors transduce light into action potentials in the eye. Mechanoreceptors respond to touch, pressure, vibration, and stretch. They are present within the skin, joints, vestibular apparatus, and cochlea. Baroreceptors detect pressure changes within the walls of blood vessels. Lastly, nociceptors detect painful stimuli throughout the body. 12. Visceral nociceptors transduce painful stimuli from deep within the body. Somatic nociceptors communicate damage at the surface of the body. Because visceral nociceptors often share neural pathways to the CNS with somatic nociceptors, visceral pain may at times trigger somatic pathways, resulting in referred pain. 13. Gustatory cells trigger primary neurons of the facial and glossopharyngeal nerves, which synapse with secondary neurons within the medulla oblongata. From the medulla, secondary neurons transmit the signal to the thalamus, where the impulse travels to the primary gustatory cortex within the insula of the cerebral cortex.

14. Odorant molecules bind to hairs on receptor cells and generate action potentials. The receptor cells then synapse with second order neurons, either mitral or tufted cells, within the olfactory bulb. Axons of the secondary neurons form the olfactory tracts, which project posteriorly to the primary olfactory cortex of the temporal lobe. 15. The sphincter pupillae and dilator pupillae muscles form the majority of the iris which adjusts the diameter of the pupil, regulating the amount of light entering the eye. 16. The lens is capable of accommodation, changing the shape lens to refract light on to the retina. Tension applied on the sensory ligaments supporting the lens flattens out the lens, allowing viewing of distant objects. Cessation of tension on the ligaments allows the lens to assume a more spherical shape, refracting the light and focusing the image on the retina. 17. Aqueous humor is secreted by the ciliary processes into the posterior chamber of the anterior cavity of the eye. It then moves from the posterior chamber, through the pupil, to the anterior chamber, where it is eventually resorbed via the scleral venous sinus. 18. The bony labyrinth consists of a series of chambers within the petrous portion of the temporal bone. The bony labyrinth is lined with a series of membranes which form the membranous labyrinth. 19. Sound waves are collected by the auricle and enter the external acoustic meatus, before striking the external surface of the tympanic membrane. Vibration of the tympanic membrane causes movement by the auditory ossicles in the middle ear. This movement results in the generation of pressure waves within the inner ear that travel through the perilymph in the scala vestibule. Pressure waves in the scala vestibule cause the vestibular membrane to vibrate, ultimately resulting in pressure wave formation in the endolymph of the cochlear duct. A region of the basilar membrane is displaced resulting in the distortion of spiral organ hair cells against the tectorial membrane, which generates an action potential. Remaining pressure waves are transferred to the scala tympani and exit the inner ear via the round window. 20. The maculae of the utricle and saccule detect linear acceleration of the head and the position of the head relative to gravity during static equilibrium. When a linear force is applied upon the otolithic membrane, its position shifts, and a force is applied to the stereocilia, distorting them. Bending of the stereocilia results in a change in the amount of neurotransmitter released from the hair cells, and a simultaneous change occurs in the stimulation of the sensory neurons of the vestibular branch of the vestibulocochlear nerve. The ampullae within the cristae ampularis of semicircular canals detect rotational acceleration. As the head accelerates, endolymph within the corresponding canal lags behind, putting pressure on the cupula. Bending of the cupula causes a deflection of stereocilia, which in turn results in a change in the amount of neurotransmitter released from the hair cells, and a simultaneous change occurs in the stimulation of the sensory neurons of the vestibular branch of the vestibulocochlear nerve.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: The sensation of taste is complemented by olfaction. Odorant molecules from the food modify the perception of its taste. 2. B Feedback: Dilation of pupils requires sympathetic stimulation from the autonomic nervous system. 3. A Feedback: Hair cells responsible for transduction of high-frequency sounds are located close to the oval window. 4. D Feedback: Macular degeneration results from physical distortion of the macula lutea, affecting the fovea centralis. 5. B Feedback: Angina pectoris often presents as pain on the left side of the body. This is referred pain from the heart projecting to the dermatomes of the left side of the chest, shoulder, or arms.

Answers to “Can You Synthesize What You’ve Learned?” 1. A middle ear infection (otis media) can often present as an ear ache, a reddened and/or bulging tympanic membrane, and possible irritation of the pharynx. This situation is common in small children, whose auditory tubes are still short and sit along a relatively horizontal plane, allowing for infection from the pharynx. 2. Smoking can lead to decreased taste sensitivity. Nicotine affects the shape of taste buds and decreases their blood supply.

3. Hyperopia, or farsightedness, results from an inability to focus light onto the retina, because the eyeball is too short. An inability to see things at a distance (myopia, or nearsightedness) also results because of an inability to focus light onto the retina, in this case, because the eyeball is too long. Corrective lens placed in front of the retina can adjust the focal plane for either condition. Convex lenses are used to correct hyperopia, bringing the focal plane anteriorly; and concave lenses are used for myopia, pushing the focal plane back posteriorly. Bifocal lenses incorporate both types to address both scenarios.

Chapter 17 Answers to “What Did You Learn?” 1. The nervous system targets specific neurons, muscles, or glands. The endocrine system targets all cells in the body that have a specific receptor. 2. Maintaining the homeostasis of blood composition, specifically blood glucose levels, is affected during diabetes mellitus. 3. The pituitary, thyroid, adrenal, pineal, and parathyroid glands are endocrine organs. The hypothalamus, skin, thymus, heart, stomach, pancreas, liver, small intestine, kidneys, testes, and ovaries have other function along with endocrine function. 4. Insulin and glucagon regulate blood glucose levels. Vitamin D, calcitonin, and parathyroid hormone affect blood calcium levels. Atrial natriuretic hormone and aldosterone regulate blood sodium levels. 5. This is an example of (a) hormonal stimulation. 6. Reproductive hormones produced in the gonads, adrenal cortex hormones, and thyroid hormones are all lipid-soluble. 7. This difference in solubility influences both the transport of the hormone in the blood and how it interacts with its target cells. 8. Paracrine secretions stimulate neighboring cells. 9. Lipid-soluble hormones do not readily dissolve within the aqueous environment of the blood. Thus, their transport in the blood requires carrier molecules. 10. As the rate of synthesis and release increases, the concentration of the hormone within the blood increases. 11. Lipid-soluble hormone receptors are usually located within the cytosol or nucleus. When formed, the hormone-receptor complex usually binds to DNA to initiate transcription. 12. Protein kinases phosphorylate molecules, either activating or deactivating them. 13. The number of receptor molecules available for hormone binding directly influences the degree of cellular response. A cell may decrease its number of receptors and reduce its sensitivity to a hormone through down-regulation. 14. Synergistic interaction occurs when the activity of one hormone reinforces the activity of another hormone. 15. Glycogenolysis and gluconeogenesis result in increased blood glucose, lypolysis introduces fatty acids and glycerol into the blood, and protein catabolism results in increased amino acids in the blood. 16. The posterior pituitary is attached to the hypothalamus by the infundibulum. 17. Neurosecretory cells within the supraoptic nucleus of the hypothalamus produce ADH, and transport the hormone in secretory vesicles along axons to terminal buds in the posterior pituitary gland, from where they can be released. 18. Thyroid-stimulating hormone is released in response to thyrotropin-stimulating hormone. Prolactin is released in response to prolactin-releasing hormone. Follicle-stimulating hormone and leutinizing hormone are released in response to gonadotropinreleasing hormone. Adrenocorticotropic hormone is released in response to corticotropin-releasing hormone. Finally, growth hormone is released in response to growth hormone–releasing hormone. 19. Growth hormone is released from the anterior pituitary in response to growth hormone–releasing hormone from the hypothalamus. Growth hormone stimulates the release of insulin-like growth factor from the liver, with both hormones having a synergistic effect on target cells. As levels of growth hormone and insulin-like growth factor increase in the blood, they provide for negative feedback by inhibiting further release of growth hormone–releasing hormone from the pituitary gland. 20. Growth hormone and insulin-like hormone increased protein synthesis, mitosis, and cell differentiation—especially in cartilage, bone, and muscle. They also increased glycogenolysis and gluconeogenesis in the liver and lipolysis in adipose tissue. 21. Thyrotropin-releasing hormone (TRH) is produced within the hypothalamus and released into the hypothalamo-hypophyseal portal system. TRH causes the release of thyroid-stimulating hormone (TSH) from the anterior pituitary gland. TSH binds to the

surface of follicular cells within the thyroid gland, permitting the release of thyroid hormone into the blood. Thyroid hormone inhibits the further release of TRH and TSH, providing for negative feedback. 22. Thyroid hormone increases protein synthesis and glucose uptake in all cells, especially neurons where it stimulates the production of the sodium-potassium pump. They also increased glycogenolysis and gluconeogenesis in the liver and lipolysis in adipose tissue. 23. In response to stress, corticotropin-releasing hormone (CRH) is released from the hypothalamus into the hypothalamohypophyseal portal system. CRH causes the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary. ACTH causes the release of cortisol from the zona fasciculata of the adrenal cortex. Increasing levels of cortisol inhibit the release of CRH and ACTH. 24. Cortisol stimulates gluconeogenesis in the liver, and lipolysis in adipocytes. Subsequently, it causes the catabolism of proteins and release of amino acids from all other tissues. 25. Pancreatic acini produce pancreatic juice as an exocrine secretion into the digestive tract. Islets of Langerhans in the pancreas produce the endocrine hormones insulin and glucagon. 26. The stimulus is humoral. 27. Beta cells in the pancreas detect increased levels of blood glucose, and respond by releasing insulin. Insulin causes the uptake of glucose by tissues of the body, thereby lowering the levels of glucose in the blood. As blood glucose levels decrease, beta cells stop the release of insulin. In this scenario, blood glucose levels are the stimulus, pancreatic beta cells are both the receptor and the control center, and insulin is the effector. 28. Glucagon causes the release of glucose into the blood. 29. Aging reduces the efficiency of endocrine system functions, and often normal levels of hormones decrease.

Answers to “Do You Know the Basics?” 1. D Feedback: The endocrine system is not directly involved in programmed cell death. 2. B Feedback: Thyroid hormone regulates the basal metabolic rate of the body. 3. D Feedback: G protein–coupled receptors, cAMP, and protein kinases are all involved in second messenger systems. 4. B Feedback: Glucagon is released from the pancreas, melatonin from the pineal gland, and epinephrine from the adrenal medulla. Growth hormone is released from the anterior pituitary gland. 5. B Feedback: Hydrophobic, not hydrophilic, hormones form complexes with intracellular receptors. 6. C Feedback: Glycogenesis is the synthesis of glycogen from glucose monomers. 7. A Feedback: Pancreatic acini produce pancreatic juice as an exocrine secretion into the digestive tract. Islets of Langerhans in the pancreas produce the endocrine hormones insulin and glucagon. 8. D Feedback: Glucocorticoids regulate the uptake of glucose from the blood. 9. C Feedback: Thyroid-stimulating hormone binds to receptors on follicular cells within the thyroid gland, stimulating the release of thyroid hormone.

10. B Feedback: Antidiuretic hormone is produced in the hypothalamus, and released from the posterior pituitary. 11. The nervous system targets specific neurons, muscles, or glands. The endocrine system targets all cells in the body that have a specific receptor. Both systems release chemical messengers to stimulate target cells. Neurons of the nervous system release neurotransmitters at specific target cells, whereas endocrine glands release their hormones into the blood. 12. The endocrine system maintains homeostasis of blood composition and volume, controls reproductive and digestive processes, and regulates development, growth, and metabolism. 13. Hormone release may be stimulated through stimulation by the nervous system (nervous), by other hormones (hormonal), or in response to levels of molecules in the blood (humoral). 14. Hormones may be steroids such as cortisol, proteins such as parathyroid hormone, or biogenic amines such as norepinephrine. Steroid hormones are the most common. 15. Local hormones do not enter the circulatory or lymphatic systems, and only affect the surrounding tissue. Circulating hormones enter circulation and travel through the body. 16. Lipid-soluble hormones do not readily dissolve within the aqueous environment of the blood, and are transported by carrier molecules. Hormone molecules continuously bind to the carrier molecule, detach from the carrier, and float free within the blood. Carrier proteins also protect hormone molecules from early destruction. 17. Water-soluble hormones cannot enter the cell. They must bind to a receptor on the extracellular surface of the membrane, which will transduce the stimulus into the cell, and activate a second messenger system. 18. Oxytocin and antidiuretic hormones are produced by neurons within the hypothalamus, transported through axons of the hypothalamo-hypophyseal tract to the posterior pituitary gland, where they are stored and eventually released as endocrine secretions. 19. Hormones produced in the endocrine tissue of the hypothalamus travel through the hypothalamo-hypophyseal portal system to the anterior pituitary gland, where they stimulate the release of trophic hormones. 20. Beta cells in the pancreas detect increased levels of blood glucose, and respond by releasing insulin. Insulin causes the uptake of glucose by tissues of the body, thereby lowering the levels of glucose in the blood. As blood glucose levels decrease, beta cells stop the release of insulin.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Hyperthyroidism can result in an enlarged thyroid gland. Increased thyroid hormone levels can cause weight loss and hyperactivity. 2. A Feedback: The thyroid gland incorporates iodine into the thyroid hormone, and stores it in follicles. 3. B Feedback: Epinephrine and cortisol are released in response to stress. Epinephrine prolongs the effects of the sympathetic nervous system, and cortisol increases the uptake and availability of nutrients. 4. C Feedback: Insulin is released in response to increased blood glucose, and causes the uptake of glucose by tissues. 5. D Feedback: Cortisol stimulates gluconeogenesis in the liver, and lipolysis in adipocytes. Subsequently, it causes the catabolism of proteins and release of amino acids from all other tissues.

Answers to “Can You Synthesize What You’ve Learned?” 1. Type I diabetes results in diminished insulin release from beta cells of the pancreas. Insulin is required to stimulate cells of the body to take up glucose, thereby lowering blood glucose levels.

2. The posterior pituitary gland releases oxytocin and antidiuretic hormone. The posterior pituitary releases the trophic hormones: thyroid-stimulating hormone, adrenocorticotropic hormone, growth hormone, luteinizing hormone, follicle-stimulating hormone, and prolactin. 3. Thyrotropin-releasing hormone (TRH) is produced within the hypothalamus and released into the hypothalamo-hypophyseal portal system. TRH causes the release of thyroid-stimulating hormone (TSH) from the anterior pituitary gland. TSH binds to the surface of follicular cells within the thyroid gland, permitting the release of thyroid hormone into the blood. Thyroid hormone inhibits the further release of TRH and TSH, providing for negative feedback.

Chapter 18 Answers to “What Did You Learn?” 1. Blood transports dissolved molecules, ions, and formed elements such as erythrocytes, leukocytes, and platelets throughout the body. 2. Blood plasma absorbs and distributes heat throughout the body. Blood vessels in the dermis can dilate and dissipate heat. Blood is capable of exchanging water with interstitial fluid and of picking up additional fluids and water from the alimentary canal. This is possible because of plasma proteins in the blood producing an oncotic gradient, regulating the movement of fluids into or out of the blood. 3. If the pH of blood is altered from the normal range, plasma proteins become denatured and are unable to carry out their functions. 4. The three layers of centrifuged blood are erythrocytes, plasma, and the buffy coat. 5. Hematocrit values vary somewhat and are dependent upon the age and sex of the individual. Adult males tend to have a hematocrit ranging between 42% and 56%, whereas adult females’ hematocrits range from 38% to 46%. 6. Plasma proteins exert osmotic pressure and prevent the loss of fluid from the blood as it moves through the capillaries. This osmotic force is responsible for drawing fluids into the blood and preventing excess fluid loss between blood capillaries and the interstitial fluid, thus maintaining blood volume and pressure. 7. Albumins are the most abundant of the blood proteins. They serve as transport vehicles for lipid-soluble molecules, and contribute to the oncotic gradient. 8. Blood contains numerous dissolved substances including electrolytes, nutrients, gases, and waste products. 9. Multi-colony-stimulating factor increases the formation of erythrocytes, as well as all classes of granulocytes, monocytes, and platelets. Granulocyte-macrophage colony-stimulating factor accelerates the formation of granulocytes and monocytes. Granulocyte colony-stimulating factor stimulates the formation of granulocytes. Macrophage colony-stimulating factor stimulates the production of monocytes. Thrombopoietin stimulates the production of megakaryocytes in the bone marrow and the subsequent formation of platelets. Erythropoietin increases the rate of production and maturation of erythrocyte progenitor and erythroblast cells. 10. Hemocytoblasts give rise to myeloid and lymphoid stem cells. Myeloid stem cells differentiate into granulocytes and monocytes. Lymphoid stem cells give rise to lymphocytes. 11. Erythrocytes are optimized for the transport of oxygen and carbon dioxide. They lack nuclei or organelles, but contain over 280 million hemoglobin molecules in their cytoplasm. They also have a biconcave shape which allows them to stack into columns rouleau as they pass through narrow vessels. Spectrin proteins in the plasma membrane allow them to flex as they enter narrow capillaries. 12. Transferrin and ferritin participate in recycling the iron ion of hemoglobin. Transferrin removes and transports the ion to the liver, where it is passed to ferritin, which stores it until it is needed and transported to the red bone marrow. 13. A person with type A blood will have A antigens on the surface of his cells and anti-B antibodies in the blood plasma. 14. Neutrophilia, an increased number of neutrophils, results in response to acute infections such as strep throat. 15. The person is healthy in terms of the white blood cell differential count. The normal range for leukocytes in the blood is 4,500 to 11,000 circulating cells per microliter, where 50–70% of the cells are neutrophils. 16. Platelets serve an important function in hemostasis (blood clotting). They circulate in the blood for 8 to 10 days. 17. During a vascular spasm a blood vessel constricts suddenly and, in so doing, limits the amount of blood that can leak from the damaged vessel. The vascular spasm phase usually lasts for several minutes. 18. Prostacyclins on the surface endothelial cells initiate pathways that prevent platelets from forming plugs in undamaged vessels. In damaged tissues, platelets adhere to exposed collagen fibers with the help of von Willebrand factor.

19. The intrinsic pathway is initiated by damage to the inside of the vessel wall and is initiated by platelets. This pathway typically takes approximately 3 to 6 minutes. In contrast, the extrinsic pathway is initiated by damage to the tissue that is outside of the vessel, and this pathway usually takes approximately 15 seconds. 20. Activated factor X combines with factors II and V, Ca2+, and platelet factor 3 to form prothrombin activator. Prothrombin activator then converts prothrombin to thrombin, which in turn converts soluble fibrinogen into insoluble fibrin. Factor XIII crosslinks and stabilizes the fibrin monomers into a fibrin polymer that serves as the “framework” of a clot. 21. The autonomic nervous system is activated once 10% of the blood volume is lost from blood vessels, causing vasoconstriction, increased heart rate, and overall increased cardiac output. 22. Fibrinolysis is the degradation of fibrin by plasmin, resulting in the destruction of fibrin framework of a clot. 23. Hemopoiesis occurs in most bones in young children, but as an individual reaches adulthood, hemopoiesis is restricted to selected bones in the axial skeleton. Fetal hemopoiesis begins in the liver and then migrates to bone marrow. 24. With age, red bone marrow is replaced by fat.

Answers to “Do You Know the Basics?” 1. B Feedback: All adult stem cells, for blood, reside within red bone marrow. 2. B Feedback: Eosinophils phagocytize antigen-antibody complexes and allergens, and also release chemical mediators to destroy parasitic worms. 3. B Feedback: Platelets are derived from megakaryocytes. 4. D Feedback: Hormones are produced by glands and tissues that have endocrine function. Endocrine hormones are transported by the blood, but are not produced in blood. 5. A Feedback: A person with type A blood only has type A antigens, and therefore has type B antibodies. 6. B Feedback: The hematocrit corresponds to the percentage of whole blood that is composed of erythrocytes. 7. C Feedback: Iron ions are required for hemoglobin to bind oxygen. 8. A Feedback: Globin proteins and erythrocyte membrane proteins are broken down into free amino acids, which may then be used to produce new proteins. 9. D Feedback: The extrinsic pathway is initiated by damage to the tissue that is outside of the vessel, compared to the intrinsic pathway which is initiated by damage to the inside of the vessel wall. 10. B Feedback: A clot starts as a network of fibrin which then traps numerous formed elements. 11. Blood plasma absorbs and distributes heat throughout the body. Blood vessels in the dermis can dilate and dissipate heat. 12. Alpha and beta globulins are integral structural components of hemoglobin. They form a heterotetramer molecule bound to four heme groups. The four iron ions within the heme groups bind oxygen to form oxyhemoglobin. The globulin molecules can also bind carbon dioxide, forming carbaminohemoglobin.

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13. The buffy coat contains leukocytes and platelets. 14. Erythrocytes have a unique biconcave disk structure that allows respiratory gases to be loaded and unloaded rapidly and efficiently. Additionally, their structure facilitates both a single-line stacking of these cells, termed a rouleau, as they pass through small blood vessels, and some flexibility of the cells to permit their passage through the smallest vessels. 15. Oxygen is transported through the blood as oxyhemoglobin, bound to the iron-containing heme groups of hemoglobin. Carbon dioxide can be transported in one of three ways: dissolved in blood plasma as carbonic acid (spontaneously disassociating into bicarbonate ions and protons), as CO2 dissolved in plasma, or bound directly to hemoglobin as carbaminohemoglobin. 16. Neutrophils have a multilobed nucleus (as many as five lobes) and cytoplasm with pale-colored granules. Eosinophils have a bilobed nucleus and cytoplasm with pink-orange to reddish granules. Basophils have a bilobed or S-shaped nucleus and cytoplasm with deep-purple granules. Lymphocytes have a round or slightly indented nucleus that fills the cell. The nucleus is darkly stained and surrounded by a thin rim of cytoplasm. These four leukocytes are about one and a half times the diameter of an erythrocyte. Monocytes have a kidney or U-shaped pale-staining nucleus with abundant cytoplasm. They are almost three times the diameter of an erythrocyte. 17. Basophils are involved in the release of histamine and heparin during anti-inflammatory or allergic reactions. Lymphocytes attack pathogens, destroy cancer cells, coordinate immune cell activity, and produce antibodies. 18. Platelets are continually produced in the red bone marrow by cells called megakaryocytes. Megakaryocytes extend long processes (proplatelets) through the blood vessel wall. These proplatelets are sliced by the force of the blood flow against the platelets. They help produce clots to prevent blood loss. 19. Formed elements in the blood are formed by hemopoiesis. Hemocytoblasts are the hemopoietic stem cells from which formed elements are derived. There are two lines of blood cell development: the myeloid line that gives rise to erythrocytes, megakaryocytes, and all leukocytes except lymphocytes, and the lymphoid line that forms the lymphocytes. 20. The three phases of hemostasis are vascular spasm, platelet plug formation, and coagulation. The vascular spasm involves constriction of the damaged blood vessel, limiting blood loss. Platelet plug formation begins with adhesion of platelets to exposed collagen fibers at the site of the damage, forming the initial plug. The subsequent coagulation phase is characterized by the production of an insoluble fibrin mesh, formed from plasma fibrinogen and numerous formed elements within the blood.

Answers to “Can You Apply What You’ve Learned?” 1. D Feedback: Taylor cannot receive blood containing the B antigen or the Rh D (Rh+) antigen. O− blood does not contain any antigens; it is the universal donor blood type. 2. A Feedback: Ibuprofen, if taken in high enough doses, can interfere with blood coagulation. 3. C Feedback: Trauma leading to the rupture of vessels will trigger the extrinsic hemostatic pathway, which will initiate the common pathway, and finally clotting. 4. C Feedback: Neutrophils defend against bacterial infections. A high neutrophil count, accompanied by a fever, would indicate a bacterial infection. 5. B Feedback: Because Taylor is Rh− and her baby is Rh+, once she was exposed to her baby’s anti-D antibodies, her body would attack any subsequent conception that was Rh+.

Answers to “Can You Synthesize What You’ve Learned?” 1. Eosinophils are granulated and readily take up eosin, a stain that makes them a pinkish-orange color. Normally, eosinophils are found within 1–4% of a differential blood count. Increased levels of eosinophils in the blood may indicate an allergic reaction, or a parasitic infection.

2. The patient would be given O− blood. O− blood does not contain any antigens of the ABO blood group, nor the Rh D antigen. It is therefore the universal donor blood type. It has no surface antigens to trigger agglutination in a recipient, regardless of blood type. 3. An athlete involved in blood doping is trying to get a competitive advantage, by artificially increasing the number of red blood cells available to the body, thereby improving cardiovascular function. This can be accomplished in one of two ways. An athlete can remove a volume of his own blood, forcing his body to produce new blood cells, and then reintroduce the original blood back into his body, thereby increasing the number of red blood cells. Another option is to inject EPO, a synthetic hormone that stimulates red blood cell production. However, there is an inherent danger in increasing the number of formed elements in the blood, thereby increasing its viscosity. This increases total peripheral resistance that may result in blood vessels forcing the heart to work harder.

Chapter 19 Answers to “What Did You Learn?” 1. A failing cardiovascular system will result in tissues that are deprived of needed oxygen and nutrients, waste product accumulation, and possible cell death. 2. All arteries carry blood away from the heart. All veins carry blood toward the heart. 3. Blood returning from the systemic circuit enters the right atrium from the superior vena cava, inferior vena cava, and the coronary sinus. It flows into the right ventricle through the right atrioventricular valve and then into the left ventricle. From the left ventricle, blood flows through the pulmonary semilunar valve and into the pulmonary trunk, which is the start of the pulmonary circuit. Blood returns to the heart from the pulmonary circuit through the pulmonary veins, and enters the left atrium. From the left atrium blood will flow through the left atrioventricular valve, into the left ventricle. From the left ventricle blood will leave the heart, through the aortic semilunar valve, into the aorta, which is the start of the systemic circuit. 4. Sustained pumping of unequal amounts of blood from the ventricles may result in edema. 5. The heart is rotated such that its right side (right atrium and ventricle) is located more anteriorly, while its left side (left atrium and ventricle) is located more posteriorly. 6. The pericardium is composed of two layers: a fibrous pericardium attached to both the sternum and the diaphragm, and an inner serous pericardium. The serous pericardium has two layers: a parietal layer that lines the inner surface of the fibrous pericardium, and a visceral layer that covers the outside of the heart. The space between the parietal and visceral layers is the pericardial cavity. 7. A relatively deep coronary sulcus extends around the circumference of the heart and separates the atria from the ventricles externally. 8. The scalpel would first pass through the fibrous pericardium, followed by the parietal layer of the pericardium, the visceral layer of the pericardium, the myocardium, and finally the endocardium. 9. The interventricular septum separates the left and right ventricles. The septum lies just deep to the interventricular sulcus, which is visible on the superficial surface of the heart. 10. Chordae tendineae are thin strands of collagen fibers that anchor into papillary muscles and attach to the cusp of the atrioventricular valves, to prevent the valve from prolapsing (inverting and flipping into the atrium) when the ventricle is contracting. 11. Cardiac muscle has features that support its great demand for energy, including an extensive blood supply, numerous mitochondria, and other structures such as myoglobin and creatine kinase It is also versatile in being able to use numerous different molecules as fuel for aerobic respiration including fatty acids, glucose, lactic acid, amino acids, and ketone bodies. 12. The fibrous skeleton of the heart acts as an electric insulator because it does not conduct action potentials and thus prevents the atrial chambers from contracting at the same time as the ventricular chambers. 13. The posterior interventricular artery provides blood to the posterior surfaces of the right and left ventricles. Blockage of the posterior interventricular artery would deprive these regions of blood. 14. The coronary sinus collects venous blood and drains deoxygenated blood from the heart wall directly into the right atrium of the heart. 15. The cells of the sinoatrial node initiate the heartbeat, and are therefore commonly referred to as the “pacemaker” of the heart. 16. The cardioacceleratory center is the origin of sympathetic innervations for the heart. Stimulation by the sympathetic division increases both heart rate and the force of heart contraction. 17. Nodal cells have a resting membrane potential of –60 mV. 18. Autorhythmicity refers to a nodal cell’s capacity to depolarize and generate an action potential without any external influence. This process involves an initial influx of Na+ into the cell through slow voltage-gated channels, open from the previous action potential. The cell depolarizes from a resting membrane potential of –60 mV to a threshold of –40mV, triggering the opening of fast voltage-gated Ca2+ channels, allowing the cell to depolarize to just above 0 mV. As Ca2+ channels close, voltage-gated K+ channels

open, allowing an influx of K+ into the nodal cell, resetting the resting membrane potential, and once again triggering the opening of slow voltage-gated Na+ channels. 19. Starting with the sinoatrial node the action potential will travel through the myocardium of the atria. It will trigger the atrioventricular node, which will in turn pass the action potential to the AV bundle, the left and right bundle branches, Purkinje fibers, and finally the myocardium of the ventricles. 20. AV nodal cells have both smaller fiber diameters and fewer numbers of gap junctions, which serve to slow down the conduction of the action potential from the atria to the ventricles. 21. Voltage-gated Ca2+ channels allow calcium to enter cardiac muscle cells. 22. (1) Depolarization of cardiac muscle cells occurs as a result of fast voltage-gated Na+ channels opening. (2) Even though slow voltage-gated K+ channels open to depolarize the cell, Ca2+ channels open, allowing an influx of Ca2+ to prolong the depolarization, producing the plateau phase of the action potential. (3) Finally, Ca2+ channels close, allowing repolarization of the cell through the continued influx of K+. 23. The plateau phase of a cardiac muscle cell contraction allows for a prolonged refractory period. This delay does not allow the summation of muscle contractions in the heart, preventing tetany. 24. The P wave reflects electrical changes of atrial depolarization. The QRS complex represents the electrical changes associated with ventricular depolarization. The T wave is the electrical change associated with ventricular repolarization. The P-Q and S-T segments represent the atrial and ventricular plateau phases, respectively. 25. Pressure changes that occur during the cardiac cycle produce the unidirectional movement of blood through the heart chambers, as well as opening and closing of heart valves to ensure that blood continues to move in a “forward” direction without backflow. 26. During late ventricular systole, semilunar valves open and ventricular ejection occurs as blood leaves the heart and enters the trunks of the aorta and pulmonary artery. 27. Increased ventricular pressure during ventricular systole causes both the closing of the atrioventricular valves and opening of the semilunar valves. 28. The end-diastolic volume is the amount of blood in a relaxed ventricle, after atrial systole. Stroke volume is the amount of blood ejected from the heart during ventricular systole. Since not all of the blood is ejected from the heart during a ventricular contraction, the volume of blood remaining in ventricles after a contraction is the end-systolic volume. 29. Cardiac output is a function of stroke volume and heart rate. 30. The resting cardiac output would be (75 beats/min × 70 mL/beat) 5.25 L/min. The cardiac output during exercise would be (150 beats/min × 100 mL/beat) 15.0 L/min. The cardiac reserve would be (15.0 L/min – 5.25 L/min) 9.75 L/min. 31. A positive chronotropic agent such as caffeine or cocaine will increase heart rate. A negative chronotropic agent such as β-blocker will decrease heart rate. 32. Entry of calcium ions into a cell brings it closer to threshold, whereas the efflux of potassium ions from a cell will hyperpolarize the cell, making it more difficult for the cell to reach threshold. 33. Increased venous return causes stretching of the heart walls, causing an increased preload, which increases the force of the subsequent contraction, and therefore increases stroke volume. Increased calcium in the sarcoplasm increases the number of ions available to bind to troponin, also increasing the force of contraction. 34. Stroke volume and heart rate have a direct relationship; therefore, as both variables increase, so does cardiac output. 35. Blood from the systemic circuit would flow from the right atrium to the left atrium through the foramen ovale, from where it would again enter into the systemic circuit, bypassing the pulmonary circuit.

Answers to “Do You Know the Basics?” 1. B Feedback: Blood returning from the systemic circuit enters the right atrium from the superior vena cava, inferior vena cava, and the coronary sinus. It flows into the right ventricle through the right atrioventricular valve and then into the left ventricle. From the left ventricle, blood flows through the pulmonary semilunar valve and into the pulmonary trunk, which is the start of the pulmonary circuit. 2. B Feedback: The pericardium is composed of two layers: a fibrous pericardium attached to both the sternum and the diaphragm, and an inner serous pericardium. The serous pericardium has two layers: a parietal layer that lines the inner surface of the fibrous pericardium, and a visceral layer, which covers the outside of the heart. The space between the parietal and visceral layers is the pericardial cavity. 3. D Feedback: The pulmonary semilunar valves prevent the backflow of blood from the pulmonary trunk, back into the right ventricle. 4. A Feedback: Blood returning from the systemic circuit enters the right atrium from the superior vena cava, inferior vena cava. Blood returning from the coronary blood supply drains to the right atrium through the coronary sinus. 5. A Feedback: An influx of calcium ions into a nodal cell causes depolarization. 6. B Feedback: Gap junctions within intercalated discs allow calcium to flow across to adjacent cardiac muscle cells, thereby propagating the action potential. 7. B Feedback: Contraction of the papillary muscles puts tension on the AV valve flaps through the chordae tendineae, thereby preventing prolapse of the valves and the subsequent backflow of blood into the atria. 8. A Feedback: The preload is a function of the end-diastolic volume, and depends upon the amount of venous return of blood to the heart. 9. D Feedback: Blood from the pulmonary trunk travels to the lungs through the pulmonary arteries. Pulmonary veins then bring blood back to the left atrium. 10. D Feedback: During the atrial reflex, increased venous return to the atria triggers sympathetic pathways that increase both the heart rate and force of contraction. 11. The pulmonary circuit carries blood from the right ventricle to the lungs and then back to the left atrium. The systemic circuit carries blood from the left ventricle through systemic arteries to all regions of the body, and then back to the left atrium through systemic veins. 12. The parietal layer of serous pericardium is a serous membrane that lines the inner surface of the fibrous pericardium, which supports the heart in the mediastinum. The visceral layer of serous pericardium (also called the epicardium) is a serous membrane that covers the outside of the heart. Together, both layers produce serous fluid in the pericardial cavity to reduce friction as the heart moves during beating. 13. Chordae tendineae are thin strands of collagen fibers that anchor into papillary muscles and attach to the cusp of the atrioventricular valves to prevent the valve from prolapsing (inverting and flipping into the atrium) when the ventricle is contracting. 14. The atria are thin walled because they do not need to generate high pressure to push blood into the ventricles. Most of the filling of the ventricles is passive, and the ventricles are inferior to the atria so moving blood into the ventricles from the atria is relatively easy. The right ventricle wall is relatively thin with respect to the left ventricle wall because the right ventricle only has to pump blood through the pulmonary circuit to the lungs immediately lateral to the heart, whereas the left ventricle must generate enough pressure to drive blood through the entire systemic circuit.

15. Intercalated discs attach adjacent cardiac muscle cells. They also contain numerous gap junctions, which allow an action potential to move continuously along the sarcolemma of adjacent cells, resulting in synchronous contraction of the muscle. 16. The right coronary artery typically branches into a marginal artery (which supplies the right border of the heart) and the posterior interventricular artery (which supplies both left and right ventricles). The left coronary artery typically branches into the anterior interventricular artery (also called the left anterior descending artery), which supplies the anterior surface of both ventricles, most of the interventricular septum, and the circumflex artery (supplies left atrium and ventricle). 17. Sympathetic innervation increases heart rate and increases the force of the heart contractions. Parasympathetic innervation will decrease the heart rate. Parasympathetic innervation tends to have no effect on the force of contractions, except in special circumstances. 18. Spontaneous depolarization of cells within the sinoatrial node initiates an action potential that is propagated through gap junction across the cells of the left and right atria, causing atrial systole. As the atria are contracting, the action potential stimulates the atrioventricular node at the base of the right atrium, from where it travels along the AV bundle, the bundle branches, and finally the Purkinje fibers. The slow conduction through the AV node ensures that the signal does not reach the ventricles until atrial diastole, at which point the Purkinje fibers generate an action potential within the myocardium of the ventricles, causing ventricular systole. 19. The phases of the cardiac cycle are atrial systole, ventricular systole (early and late), and ventricular diastole (early and late). (1) During atrial systole, the atria contract to pump blood into the ventricles to finish their filling. The AV valves remain open and the ventricles are still in diastole from the previous cycle. The semilunar valves remain closed. (2) During early ventricular systole, the atria are now in diastole, the ventricles begin to contract, and the AV valves close. The semilunar valves remain closed for a short period of time and then they are forced open. (3) During late ventricular systole, the atria remain in diastole, the ventricles continue contracting, the AV valves remain closed, and the semilunar valves remain open. (4) During early ventricular diastole, the atria remain in diastole, the ventricles enter diastole, the semilunar valves close, and the AV valves remain closed for a short period of time and then they open. (5) During late ventricular diastole, the atria remain in diastole, the AV valves remain open, the ventricles passively fill with blood, and the semilunar valves remain closed. 20. Cardiac output is the amount of blood ejected from the heart in 1 minute. It is a function of the amount of blood ejected with each contraction (stroke volume) and the number of times that the heart contracts per minute (heart rate).

Answers to “Can You Apply What You’ve Learned?” 1. D Feedback: Tachycardia may result in inefficient cardiac output because of a decreased ejection fraction, resulting in an increased endsystolic volume. 2. B Feedback: Blood pressure monitoring would give an indication of the state of the circulatory system, which although influenced by the heart, is not a good indicator of heart health. 3. C Feedback: Calcium channel blockers cause a negative ionotropic effect, decreasing the contractility of the heart, and subsequently decreasing cardiac output. 4. D Feedback: Decreased blood volume will cause decreased end-diastolic volume. Low end-diastolic volume will result in decreased stroke volume, and subsequent decreased cardiac output. The body will try to maintain cardiac output by increasing the heart rate. 5. B Feedback: Severing the vagus nerve will result in loss of vagal tone, allowing the SA node to increase the rate of contraction to either its own inherent pace or the pace set by any sympathetic stimulation.

Answers to “Can You Synthesize What You’ve Learned?” 1. Under normal conditions, in a fully developed heart, deoxygenated blood returning from the systemic circuit enters the right atrium from the superior vena cava, inferior vena cava, and the coronary sinus. It flows into the right ventricle through the right atrioventricular valve and then into the left ventricle. From the left ventricle, blood flows through the pulmonary semilunar valve and into the pulmonary trunk, which the start of the pulmonary circuit. Oxygenated blood returns to the heart from the pulmonary circuit through the pulmonary veins, and enters the left atrium. From the left atrium blood will flow through the left atrioventricular valve, into the left ventricle. From the left ventricle blood will leave the heart, through the aortic semilunar valve, into the aorta, which is the

start of the systemic circuit. With the foramen ovale open, deoxygenated blood from the systemic circuit would flow from the right atrium to the left atrium through the foramen ovale, from where it would again enter into the systemic circuit, bypassing the pulmonary circuit. 2. Angina pectoris results from diminished blood supply to the myocardium, usually caused by occlusion of blood flow through coronary arteries. It presents as pain on the left side of the body, usually the arm, jaw, or shoulder. This is an example of referred pain, which results from the merging of sensory stimuli originating due to lactic acid accumulation in the myocardium, with somatosensory stimuli from the left side of the body. 3. If the SA node is not functioning, the atria do not contract; fortunately, they only contribute a small fraction to the total enddiastolic volume. The ventricles would continue to contract because the AV node becomes the “default” pacemaker, and establishes the heart rate.

Chapter 20 Answers to “What Did You Learn?” 1. Arteries are usually thicker than companion veins. Arteries also have a predominant tunica media. Without a predominant layer of smooth muscle, by default, veins have a predominant tunica externa. Finally, veins have one-way valves, whereas arteries do not. 2. As arteries branch on to progressively smaller vessels their luminal diameter decreases. The composition of the tunics also changes, with a decrease in the amount of elastic fibers, and an increase in the amount of smooth muscle present in the walls of the arteries. 3. Sinusoids are the most permeable capillaries. They are located within bone marrow, liver, spleen, anterior pituitary gland, adrenal gland, and parathyroid glands. 4. Because veins contain over 55% of all of the blood within the body, they serve as reservoirs for blood. 5. There are four alternatives to a simple pathway of blood flow. The simple pattern involves blood flowing through an arteriole to a capillary bed, and out of the capillaries through a venule. An arterial anastomosis includes two or more arteries converging to supply the same body region. Similarly, a venous anastomosis includes two or more veins draining the same body region. An arteriovenous anastomosis is a shunt, bypassing a capillary bed by connecting an arteriole directly to a vein. Portal system blood flows through two capillary beds, with the two capillary beds separated by a portal vein. 6. Water-soluble substances such as carbon dioxide, oxygen, waste products, hormones, and nutrients enter or leave capillaries by diffusion. Lipid-soluble hormones and other molecules such as fatty acids utilize vesicular transport to enter or leave capillaries. 7. Hydrostatic pressure is the physical force exerted by a fluid on a structure. In contrast, osmotic pressure is the pull of water into an area by osmosis due to the higher relative concentration of solutes. 8. Blood hydrostatic pressure is greater at the arterial end of the capillary (35 mm Hg) and less at the venous end (16 mm Hg). In contrast, the net colloid osmotic pressures remain relatively constant (21 mm Hg). 9. The blood hydrostatic pressure is the greatest force at the arterial end of the capillary. This results in positive net filtration pressure, forcing fluids out of the capillary. At the venous end, the greatest force is due to the blood colloid osmotic pressure, resulting in a negative net filtration pressure, forcing fluids into the capillary. 10. Without functional lymphatic vessels, the excess 15% of fluid not reabsorbed by capillaries would accumulate within the tissue, causing edema. 11. Angiogenesis is stimulated in skeletal muscle in response to aerobic training, in adipose tissue. Angiogenesis occurs when an individual gains weight in the form of fat deposits. 12. Carbon dioxide, H+, K+, and lactic acids are by-products of cellular metabolism. As the metabolic rate increases, so do the levels of these by-products, which in turn act as local signals causing vasodilation, and increased blood flow to the tissue. 13. Total blood flow is a function of cardiac output. As total blood flow increases, so does the local blood flow to a tissue. 14. The pulse pressure is (155 mm Hg – 95 mm Hg) 60 mm Hg. The mean arterial pressure is (95 mm Hg + [1/3 × 60 mm Hg]) 115 mm Hg. 15. Capillary blood pressure must be sufficient for exchange of substances between the blood and surrounding tissue, but not be so high that it would damage the fragile vessels. 16. The relatively small pressure gradient (20 mm Hg) of veins is overcome by the respiratory pump and the skeletal muscle pump. The skeletal muscle pump entails movement of limbs, which compresses vessels in propelling blood. This movement is restricted to only one direction by one-way venous check valves. The respiratory pump carries out a similar role in the thoracic cavity, fluctuating intrathoracic pressure with each breath, and thereby compressing blood vessels. 17. The pressure gradient of systemic circulation is calculated by subtracting the mean arterial pressure in the vena cava from that of arteries near the aorta. This blood pressure gradient is the driving force to move blood through the vasculature. Changes in the blood pressure gradient are directly correlated with changes in total blood flow.

18. Resistance is defined as the amount of friction the blood experiences as it travels through the blood vessels. 19. There is a direct relationship between the viscosity of blood and resistance. As viscosity increases, so does resistance. A similar relationship exists between vessel length and resistance. There is an inverse relationship between the diameter of blood vessels and resistance. As diameter decreases, resistance increases. 20. Individuals with sustained increased resistance generally exhibit elevated arterial blood pressure readings. This condition occurs because a greater pressure gradient must be produced to overcome the higher resistance and ensure normal blood flow and adequate perfusion of all tissues. 21. Short-term mechanisms for regulating blood pressure are important when a person arises from a sitting to a standing position. 22. As a person arises to a standing position her blood pressure will initially drop, but then be quickly reestablished to normal levels through the following mechanism: (1) Decreased stretch in the blood vessel wall is detected by baroreceptors in aortic arch baroreceptors and carotid sinuses. (2) The baroreceptors decrease their firing rate along the vagus and glossopharyngeal nerves, signaling the cardiovascular center in the medulla oblongata. (3) The cardioacceleratory center of the cardiac center increases stimulation to the SA and AV nodes, increasing cardiac output, while at the same time the cardioinhibitory center decreases parasympathetic stimulation. (4) Simultaneously, the vasomotor center stimulates vasoconstriction and an increase in peripheral resistance, along with shifting of blood from venous reservoirs. The resulting increase in cardiac output, increase in resistance, and larger circulating blood volume quickly elevate blood pressure. 23. Renin produced by the kidneys converts angiotensinogen into angiotensin I. Angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme, found primarily within the endothelium of capillaries in the lungs. Angiotensin II raises blood pressure by causing vasoconstriction, causes a sensation of thirst, and induces the release of aldosterone and antidiuretic hormone. Since both of these hormones cause fluid retention in the kidneys, they increase blood volume and therefore raise blood pressure. 24. Atrial natriuretic peptide causes vasodilation, which lowers the total peripheral resistance, increases urine production, and ultimately decreases blood pressure. 25. Blood flow velocity decreases significantly in capillaries that have a decreased total cross-sectional area, a measurement that takes into consideration the total length of capillaries in the body, along with their diameters. 26. During exercise blood is diverted from the kidneys and digestive system to the coronary arteries, skeletal muscles, and skin. 27. All of the blood returning from the systemic circuit must eventually be pumped to the pulmonary circuit (accounting for endsystolic volume of the right ventricle). 28. Blood pressure is lower throughout the pulmonary circulation in comparison to the systemic circulation. 29. The brachiocephalic trunk supplies blood to the right arm, the right side of the face, and the brain. The left coronary artery supplies blood to the left side of the face and the brain, and the left subclavian artery provides blood to the left arm. 30. The superior vena cava drains the head, neck, upper limbs, and thoracic cavity. The inferior vena cava carries blood toward the heart from the lower limbs, pelvis, perineum, and abdomen. 31. The vertebral artery, thyrocervical trunk, and costocervical trunk branch off of the subclavian artery to provide blood supply to the head and neck. These regions are then drained by the vertebral, internal jugular, and external jugular veins. 32. Most of the venous blood of the cranium drains through the dural venous sinuses into the internal jugular veins. 33. The azygous system drains into the superior vena cava. 34. The bronchi, bronchioles, and connective tissue of the lungs are supplied with oxygenated blood by the bronchial arteries. 35. The celiac trunk branches into the common hepatic, left gastric, and splenic arteries. The common hepatic artery supplies blood to the liver, gallbladder, duodenum, as well as parts of the pancreas and stomach. The left gastric artery supplies blood to parts of the stomach and esophagus. The splenic artery supplies blood to the spleen, and part of the pancreas and stomach.

36. The splenic, inferior mesenteric, and superior mesenteric veins drain into the hepatic portal system. The hepatic portal system passes blood from organs of digestion and the spleen through the liver before entering the systemic circuit. 37. The kidneys receive blood through the renal arteries. The adrenal glands receive blood from the renal, middle suprarenal, and inferior phrenic arteries. The female uterus receives blood through the uterine artery. 38. From the subclavian artery blood will flow through the axillary artery, the brachial artery, then through either the ulnar or radial arteries, to the deep palmar arch, and finally to the digital arteries of the thumb. 39. The primary superficial veins of the upper limbs include the basilic, cephalic, and median cubital veins. 40. From the external iliac artery blood will flow into the femoral artery, through the popliteal artery, the anterior tibial artery, the dorsal pedis artery, the plantar arterial arch, and finally the digital arteries of the foot. 41. The great saphenous vein runs the length of the leg, and is significantly longer than the small saphenous vein, which joins the femoral vein within the popliteal region. 42. The umbilical vein delivers oxygenated blood from the placenta to the fetus. The ductus venosus shunts blood from the umbilical vein to the inferior vena cava, bypassing the fetal liver. Blood is shunted from the right atrium to the left atrium of the fetal heart through the foramen ovale, bypassing the pulmonary circuit. Any blood that does enter the fetal pulmonary circuit is shunted from the pulmonary trunk to the aorta by the ductus arteriosus. Blood returns to the placenta from the fetus through the umbilical arteries. 43. The ductus arteriosus and foramen ovale must close after birth in order to completely engage the pulmonary circuit of the neonate.

Answers to “Do You Know the Basics?” 1. B Feedback: Sinusoids are very unselective, and are not found in the brain. 2. C Feedback: Without a predominant layer of smooth muscle, by default, veins have a predominant tunica externa. 3. C Feedback: Vasa vasorum provide arterial blood to the tunica externa of a large vessel. 4. A Feedback: Decreased blood flow will decrease the amount of blood reaching a region, decreasing perfusion. Increased carbon dioxide, H+, or decreased O2 levels cause vasodilation, which ultimately improves perfusion of a tissue. Angiogenesis also provides more blood flow to a region, increasing perfusion. 5. B Feedback: The relatively small pressure gradient of veins is overcome by the respiratory pump and the skeletal muscle pump. 6. B Feedback: Increasing diameter will decrease resistance, increasing blood flow. 7. D Feedback: Total blood flow is important for maintaining adequate perfusion of a tissue. It increases with increasing pressure, but decreases against increasing resistance. 8. B Feedback: Blood flow velocity decreases significantly in capillaries which have a decreased total cross-sectional area, a measurement that takes into consideration the total length of capillaries in the body, along with their diameters. 9. D Feedback: Blood pressure is regulated by the cardiovascular center of the medulla oblongata, through the autonomic nervous system. It can also be adjusted by hormones such as epinephrine, antidiuretic hormone, aldosterone, atrial natriuretic peptide, or angiotensin.

10. D Feedback: From the subclavian artery blood will flow through the axillary artery, the brachial artery, then through either the ulnar or radial arteries. 11. The tunica intima consists of an endothelium of simple squamous connective tissue, lined by a subendothelial layer of areolar connective tissue. The tunica media is composed predominantly of layers of smooth muscle. The tunica externa consists primarily of dense irregular connective tissue. 12. Arteries transport blood away from the heart. Veins return blood to the heart. Relative to veins, arteries have smaller luminal diameters and experience greater pressures. The tunica media is the predominant layer in arteries. Without a predominant layer of smooth muscle, by default, veins have a predominant tunica externa. 13. Hydrostatic pressure is the physical force exerted by a fluid on a structure. In contrast, osmotic pressure is the pull of water into an area by osmosis due to the higher relative concentration of solutes. Blood hydrostatic pressure is greater at the arterial end of the capillary (35 mm Hg) and less at the venous end (16 mm Hg). In contrast, the net colloid osmotic pressures remain relatively constant (21 mm Hg). 14. NFP = (HPb − HPif) − (COPb − COPif) 15. Blood flow decreases in longer vessels and increases in smaller vessels. However, since there are more smaller vessels than larger vessels, as the total cross-sectional area decreases so does blood flow. The viscosity of blood has inverse relationship with blood pressure. Increased blood viscosity decreases blood flow. Conversely, increased blood pressure increases blood flow. 16. Blood vessels containing α-adrenergic receptors contract in response to sympathetic stimulation, resulting in vasoconstriction; these include most vessels of the body. In contrast, blood vessels with β receptors relax in response to epinephrine, resulting in vasodilation; these include blood vessels in skeletal muscle and the coronary vessels. 17. Increased blood volume, increased cardiac output, and increased resistance will all raise blood pressure. 18. The cardiac center increases stroke volume and heart rate, thereby increasing cardiac output, and consequently raising blood pressure and blood flow. The vasomotor center regulates the degree of vasoconstriction, adjusting resistance in blood vessels, and subsequently adjusting blood pressure and blood flow. 19. In the systemic circuit arteries carry oxygenated blood away from the heart, to various parts of the body, and veins return deoxygenated blood back to the heart. In the pulmonary circuit arteries carry deoxygenated blood to the lungs, and pulmonary veins bring oxygenated blood back to the heart. 20. Postnatal changes to the circulatory system include constriction of the umbilical veins, umbilical arteries, and ductus venosus, so that they are no longer functional, and closure of the foramen ovale and ductus arteriosus. These changes are necessary in order to completely engage the neonate’s pulmonary circulation.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Albumin is the main plasma protein required for establishing the colloid osmotic pressure. Insufficient colloid osmotic pressure will not affect hydrostatic pressure, so blood will still leave capillaries, but it will not be drawn back in sufficiently, resulting in edema. 2. B Feedback: Exercise will cause an increase in blood pressure. Atrial natriuretic peptide lowers blood pressure by causing vasodilation. 3. D Feedback: Decreased blood supply to the brain can cause dizziness and possibly syncope (fainting). The carotid sinus detects changes in blood pressure en route to the brain and then signals the cardiovascular center in the medulla oblongata. The cardiovascular center adjusts cardiac output and vasoconstriction accordingly, to maintain adequate blood flow to the brain. 4. A Feedback: Storage of excess fat requires angiogenesis, increasing the overall length of the blood supply. Increasing length lowers blood flow, which must be compensated for by increasing other factors such as cardiac output, in order to restore blood flow. Losing fat reduces the blood flow necessary to maintain the adipose tissue, and therefore lowers blood pressure.

5. D Feedback: The popliteal artery is the origin of three collateral channels—the anterior tibial, posterior tibial and fibular arteries— which all anastamose at the foot.

Answers to “Can You Synthesize What You’ve Learned?” 1. Hypertension may cause damage to the endothelium of blood vessels. An inflammatory response to the damaged endothelium leads to a buildup of plaque within the walls of the artery. Low-density lipoproteins and very-low-density lipoproteins infiltrate and get trapped within the damaged tissue and become oxidized. These oxidized proteins, along with invading monocytes, turn lipids in the tunica intima into foam cells, which are then replaced by muscle tissue. This expanding mass of oxidized lipids and smooth muscle tissue is called an atheroma. As it expands, it can occlude the lumen of the artery, a condition called atherosclerosis. 2. Flexion at a joint can occlude blood flow through arteries in the region. Anastomoses at joints provide for alternative blood flow when vessels are occluded due to flexion. 3. Increased deposits of adipose tissue due to weight gain require angiogenesis to provide blood flow to the new tissue. This increases the total length of the vasculature, and subsequently increases resistance to cardiac output from the heart. As resistance increases, cardiac output must be increased, which raises blood pressure.

Chapter 21 Answers to “What Did You Learn?” 1. Lymphatic capillaries typically absorb water, dissolved solutes, and small amounts of protein. 2. The hydrostatic pressure of interstitial fluid separates the endothelial cells that form the lymphatic capillaries, allowing the interstitial fluid to enter the capillary. Once inside, the fluid exerts pressure on the endothelial cells, closing the gaps, and trapping the fluid in the vessel. 3. The lymphatic trunks drain lymph from various regions of the body. The trunks merge into one of two distinct lymphatic ducts. Each duct then returns the fluid back to the systemic circuit of the circulatory system. 4. The right lymphatic duct receives lymph from (1) the right side of the head and neck, (2) the right upper limb, and (3) the right side of the thorax. 5. Primary lymphatic structures, such as bone marrow and thymus, are involved in the formation and maturation of lymphocytes. Secondary lymphatic structures' immune cells follow their formation and provide the site where an immune response is initiated. The major secondary lymphatic structures include the lymph nodes, spleen, tonsils, lymphatic nodules, and MALT. 6. Red bone marrow is the site of production of all formed elements in the blood, including all lymphocytes; hence it is a primary lymphatic structure. 7. The cortex of the thymus contains immature T-lymphocytes (pre-T-lymphocytes), and the medulla contains mature T-lymphocytes. 8. Numerous lymphatic vessels will deliver lymphatic fluid to a lymph node. As the materials within the fluid percolate through the sinuses located in the medulla of the lymph node, they will be exposed to macrophages and lymphocytes. Macrophages will remove foreign particles from the lymphatic fluid. Lymphocytes will initiate an immune response upon exposure to the foreign particles. 9. The spleen is responsible for the filtration of blood. The white pulp of the spleen contains lymphocytes which monitor the blood for pathogens, and are capable of initiating an immune response. The red pulp within the sinusoids of the spleen contains macrophages, which remove foreign substances, pathogens, and either old or defective erythrocytes and platelets. 10. Lymph nodes filter lymph, whereas the spleen filters blood. 11. The three sets of tonsils are the pharyngeal, palatine, and lingual tonsils. Tonsils help protect against foreign substances that may be either inhaled or ingested. 12. The lymphatic cells in the MALT help defend against foreign substances that come in contact with mucosal membranes.

Answers to “Do You Know the Basics?” 1. B Feedback: The lymphatic system provides for an alternative route for the return of fluid toward the heart in the systemic circuit. It also provides an opportunity for lymphocytes and macrophages to filter and process body fluids. 2. A Feedback: The thoracic duct drains lymph from the right side of the head, neck, right arm, and the right side the thoracic cavity. 3. C Feedback: Lymphatic structures have an opening within their connective tissue coverings, which permit either lymphatic vessels or blood vessels to enter and leave the organs. 4. A Feedback: Although immature T-lymphocytes originate within red bone marrow, they complete maturation within the thymus. 5. B Feedback: Lymphatic capillaries are homologous with blood capillaries, in that they consist of a simple endothelial layer. Unlike blood capillaries, they also possess one-way flaps that allow interstitial fluid to enter the lymphatic system.

6. C Feedback: Numerous lymphatic vessels will deliver lymphatic fluid to a lymph node. As the materials within the fluid percolate through the sinuses located in the medulla of the lymph node, they will be exposed to macrophages and lymphocytes. Division of lymphocyte in response to an infection may cause the lymph node to swell and become tender. 7. B Feedback: The spleen filters pathogens if they are in the circulatory system. 8. C Feedback: The spleen is not involved in hemopoiesis. On the contrary, it is responsible for removing old or defective formed elements such as erythrocytes and platelets from the blood. 9. D Feedback: The spleen is responsible for removing old or defective formed elements such as erythrocytes and platelets from the blood. 10. D Feedback: Numerous lymphatic vessels will deliver lymphatic fluid to a lymph node. As the materials within the fluid percolate through the sinuses of the lymph node, they will be exposed to macrophages and lymphocytes. 11. The lymphatic vessels include lymphatic capillaries, lymphatic trunks, and lymphatic ducts. Red bone marrow and the thymus are considered as primary lymphatic structures. Secondary lymphatic structures include tonsils, MALT, lymph nodes, and the spleen. 12. Primary lymphatic structures, such as bone marrow and thymus, are involved in the formation and maturation of lymphocytes. Secondary lymphatic structures' immune cells follow their formation and provide the site where an immune response is initiated. The major secondary lymphatic structures include the lymph nodes, spleen, tonsils, lymphatic nodules, and MALT. 13. Interstitial fluid enters lymphatic capillaries and becomes lymph.

14. The thoracic duct drains lymph from the right side of the head and neck, right arm, and the right side of the thoracic cavity. 15. The thymus continues to grow until puberty, when it reaches a maximum weight of 30 to 50 grams. Cells within the thymus begin to regress after it reaches this size. Thereafter, much of the thymic tissue is replaced by adipose connective tissue. 16. Numerous lymphatic vessels will deliver lymphatic fluid to a lymph node. As the materials within the fluid percolate through the sinuses located in the medulla of the lymph node, they will be exposed to macrophages and lymphocytes. Macrophages will remove foreign particles from the lymphatic fluid. Lymphocytes will initiate an immune response upon exposure to the foreign particles. 17. The white pulp of the spleen contains lymphocytes which monitor the blood for pathogens, and are capable of initiating an immune response. The red pulp within the sinusoids of the spleen contains macrophages, which remove foreign substances, pathogens, and either old or defective erythrocytes and platelets. 18. A pharyngeal tonsil is found in the posterior wall of the nasopharynx, palatine tonsils are located in the posterolateral region of the oral cavity, and the lingual tonsils are located along the posterior one third of the tongue. 19. Lymphatic nodules are small clusters of lymphatic cells with some extracellular matrix that are not completely surrounded by a connective tissue capsule. They are located within every organ of the body. They may also aggregate into larger structures such as MALT, which is found in mucous membranes of the digestive and respiratory systems. 20. The lymphatic system provides for an alternative route for the return of fluid toward the heart in the systemic circuit. It also provides an opportunity for lymphocytes and macrophages to filter and process body fluids.

Answers to “Can You Apply What You’ve Learned?” 1. A Feedback: Lymph from the head must drain through lymph nodes in the cervical region.

2. D Feedback: The thymus is responsible for the maturation of T-lymphocytes. 3. B Feedback: The spleen is responsible for filtering pathogens from the blood. 4. A Feedback: Axillary lymph nodes, which drain fluid from the arms and axilla, are often removed during a mastectomy. 5. D Feedback: Obstruction or removal of lymph nodes or vessels will inhibit drainage of fluid by the lymphatic system. Exercise will cause increased hydrostatic pressure in blood capillaries, which will cause an increase in interstitial fluid. This fluid will create greater hydrostatic pressure on lymph capillaries, forcing the fluid into lymph capillaries, therefore preventing edema.

Answers to “Can You Synthesize What You’ve Learned?” 1. The doctor was checking for an enlargement of her spleen. The white pulp of the spleen contains lymphocytes which monitor the blood for pathogens, and are capable of initiating an immune response. The red pulp within the sinusoids of the spleen contains macrophages, which remove foreign substances, or pathogens. Activation of B-lymphocytes in the white pulp in response to mononucleosis may cause an enlargement of the organ. 2. Lymphatic capillaries are highly unselective. Filtration in the lymphatic system does not occur until lymph reaches the lymph nodes. Metastatic cells can readily enter lymphatic capillaries and establish new tumors within lymph nodes. 3. Medical guidelines suggest performing a tonsillectomy only if the person has had seven throat infections in 1 year, five infections in 2 years, or three infections per year for 3 years.

Chapter 22 Answers to “What Did You Learn?” 1. Bacteria consist of prokaryotic cells. Viruses are not cells, and must enter a cell in order to replicate. 2. T-lymphocytes, B-lymphocytes, macrophages, and NK cells are located within secondary lymphatic structures. Epidermal dendritic cells and mast cells are located in the skin. Mast cells are also located within mucosal linings of the respiratory, digestive, and urogenital tracts. 3. Cytokines are small, soluble proteins produced by cells of the immune system in order to regulate and facilitate immune system activity. Cytokines act like hormones, in that they are released from one cell and bind to a specific receptor on a target cell. 4. Adaptive immunity involves T-lymphocytes and B-lymphocytes. 5. The skin and mucosal membranes act as physical barriers to infection. They also possess normal bacterial flora that prevent the growth of pathogenic microorganisms. 6. Neutrophils and macrophages destroy infectious agents and cellular debris by phagocytosis. Neutrophils are first to respond to an infection. Once monocytes leave the circulatory system, they become macrophages, which arrive later than neutrophils, but are present longer at the site of infection. Basophils and mast cells both release granules that illicit an inflammatory response. Basophils are found within blood, whereas mast cells are found within the linings of mucosal or cutaneous membranes. 7. NK cells make physical contact with unhealthy cells and release cytotoxic chemicals. Perforin released from NK cells inserts transmembrane pores into target cells, and granzymes initiate apoptosis (programmed cell death). 8. The complement system consists of a series of plasma proteins which are selectively activated, and then initiate a series of defensive mechanisms, in response to an infection. There are four such mechanisms: (1) opsonization, (2) inflammation, (3) cytolysis, and (4) the elimination of immune complexes. 9. Inflammation is an immediate, local, nonspecific event that occurs in vascularized tissue in response to a variety of injury-induced stimuli. The first step in the immune response is the release of inflammatory and chemotactic factors from damaged cells at the site of the injury. This is followed by vasodilation and increased capillary permeability at the site. Increased fluid in the tissue facilitates the recruitment of immune cells from the blood, into the interstitial space, as well as the release of immunoglobulins and clotting proteins. 10. Exudate delivers cells and substances needed to eliminate the injurious agent and promote healing. 11. A fever is defined as an abnormal elevation of body temperature of at least 1°C from the typically accepted core body temperature. At the onset of a fever, the hypothalamus stimulates the retention of heat at the skin, as well as shivering in order to generate more heat. At the stadium stage, the metabolic rate is increased to promote elimination of pathogens. In the defervescence stage the temperature returns to normal, as the hypothalamus reverses heat retention mechanisms in order to return the body to its normal temperature. 12. A fever inhibits reproduction of bacteria and viruses, promotes interferon activity, increases activity of adaptive immunity, and accelerates tissue repair. Fevers can be potentially dangerous because of changes to metabolic pathways and denaturation of body proteins. Seizures may occur at sustained body temperatures above 102oF, irreversible brain damage may occur at body temperatures that are sustained at greater than 106oF, and death is likely when body temperature reaches 109oF. 13. The specific site on the antigen molecule that is recognized by components of the immune system is referred to as the antigenic determinant. 14. Haptens are too small to trigger the immune system. A hapten must first bind to a carrier molecule before it can become an antigen in an immune response. 15. The receptor complexes of T-lymphocytes and B-lymphocytes differ in that BCRs are capable of making direct contact with antigen, whereas TCRs are not. A TCR requires initial processing and presentation of the antigen before making contact. Tlymphocytes also possess CD receptors, which act as coreceptors to facilitate interaction with the antigen. Helper T-lymphocytes have the CD4 isoform of the coreceptor. Cytotoxic T-lymphocytes carry the CD8 isoform. 16. All nucleated cells present antigen with MHC class I molecules. MHC class II is only found in antigen presenting cells (APCs).

17. Lymphocytes typically encounter antigens for the first time within secondary lymphatic organs such as the lymph nodes, spleen, tonsils, or MALT. 18. Maturation of T-lymphocytes takes place in the thymus. 19. A T-lymphocyte that fails negative selection must be eliminated so that it does not initiate an autoimmune response. 20. Naive T-lymphocytes are housed within secondary lymphatic organs, following maturation in the thymus. 21. Secondary stimulation by the release of IL-2 from helper T-lymphocytes is required for the activation of helper T-lymphocytes (autocrine process) or cytotoxic T-lymphocytes (endocrine process). 22. Interleukin-2 released from helper T-lymphocytes stimulates the cells to proliferate into activated helper T-lymphocytes and memory helper T-lymphocytes. Similarly, IL-2 from helper T-lymphocytes stimulates cytotoxic T-lymphocytes to divide and differentiate into clones, activated cytotoxic T-lymphocytes, and memory cytotoxic T-lymphocytes. 23. B-lymphocytes do not require antigen to be presented by other nonlymphocyte cells. A B-lymphocyte is able to serve the role of an APC. 24. Cytokine released from helper T-cells stimulates B-lymphocytes to proliferate, and differentiates into either activated Blymphocytes or memory B-lymphocytes. 25. Lymphocyte recirculation provides a means of delivering different lymphocytes to secondary lymphatic structures, making it more likely that a lymphocyte will encounter its antigen, if present. 26. Helper T-lymphocytes release IL-2 and other cytokines that regulate cells of both adaptive and innate immunity. 27. Cell-mediated immunity is effective against foreign cells, such as virus-infected cells, bacteria-infected cells, tumor cells, or foreign transplanted cells. 28. Plasma cells produce antibodies against specific antigens. 29. The variable regions located at the ends of the arm of the antibody contain the antigen-binding site, which attach to a specific antigenic determinant of an antigen. 30. Neutralization, agglutination, and precipitation occur due to the binding of antibody-antigen binding sites to antigens. Complement fixation, opsonization, and activation of NK cells result from an exposure of the Fc region of the antibody, after binding to an antigen. 31. IgG is the most prevalent class of immunoglobulins. They have the most diverse range of function, including neutralization of viruses, bacteria, and toxins, agglutination, precipitation, complement activation, opsonization, and natural killer cell activation. 32. An initial antigen challenge causes the production of memory B- and T-lymphocytes. On subsequent exposures to the antigen, these memory cells make contact with the antigen more rapidly and produce a more powerful response. 33. Secondary responses have a much shorter lag phase, with antibody production rising very quickly, when compared to a primary response. During secondary responses the pathogen is typically eliminated even before disease symptoms develop. 34. Active immunity results in the production of memory cells and provides longer protection from an antigen.

Answers to “Do You Know the Basics?” 1. B Feedback: T-lymphocytes are not phagocytic, but instead are involved in cell-mediated adaptive immunity. 2. B Feedback: Helper T-lymphocytes release IL-2, which induces the differentiation and proliferation of B-lymphocytes.

3. C Feedback: A naive B-lymphocyte first binds free antigens, which it processes and presents to an activated helper T-lymphocyte via a MHC class II molecule. The helper ZT-lymphocyte then releases interleukin-2, which stimulates the differentiation of B-lymphocytes into populations of memory and activated cells. 4. A Feedback: NK cells and cytotoxic T-lymphocytes release cytokines that trigger apoptosis in target cells. 5. B Feedback: The antigen is not destroyed by the antibody. The antibody will bind to the antigen and illicit a specific response, but it does not destroy it. 6. D Feedback: Lymphocytes are very specific for distinct antigens. 7. C Feedback: During inflammation, vasodilation and increased permeability of capillaries allow extra fluid from blood to wash through the affected area, before being drained by lymphatic capillaries. 8. A Feedback: Interferon is released from cells infected with viruses, stimulating an immune response, and helping to protect neighboring cells from infection. 9. D Feedback: After formation in red bone marrow, immune cells must be activated in secondary lymphatic organs, only then can they participate in immunologic defense. 10. A Feedback: Complement helps to elicit an inflammatory response and cytolysis. 11. Innate immunity provides an immediate response to a wide array of infectious or toxic substances. It utilizes protective barriers such as mucous and cutaneous membranes, nonspecific macrophages, and cytotoxic NK cells. Non-cell-specific events such as inflammation and fevers are also involved. Adaptive immunity, although initially a slower response, allows the body to learn to recognize specific antigens, thereby providing for a faster defense upon subsequent exposures. Adaptive immunity requires the interactions of T-lymphocytes, B-lymphocytes, and plasma cells. 12. Inflammation is an immediate, local, nonspecific event that occurs in vascularized tissue against a variety of injury-induced stimuli. The first step in the immune response is the release of inflammatory and chemotactic factors from damaged cells at the site of the injury. This is followed by vasodilation and increased capillary permeability at the site. Increased fluid in the tissue facilitates the recruitment of immune cells from the blood, into the interstitial space, as well as the release of immunoglobulins and clotting proteins. The additional fluid also helps to remove cellular debris and pathogens, into the lymphatic system. 13. An antigen is a structural feature of a foreign particle that is recognized by components of active immunity. 14. Major histocompatibility complexes are glycoproteins that bind antigens. MHC class I molecules may present either self-antigens or foreign antigens, if produced by an infected cell. MHC class II molecules only present foreign antigens. These complexes are then used to select for T-lymphocytes that recognize foreign antigens, and to select against T-lymphocytes that target self-antigens. 15. Positive selection selects for T-lymphocytes that recognize foreign antigens. Negative selection eliminates T-lymphocytes that target self-antigens. 16. Helper T-lymphocytes regulate differentiation and proliferation of both B-lymphocytes and other T-lymphocytes into active or memory cells. 17. Cytotoxic T-lymphocytes recognize antigens presented by infected cells, and destroy the infected cells by inserting perforin protein into their plasma membranes, or by introducing granzymes into the cells, which induce apoptosis.

18. The Fc region of IgG and IgM antibodies can bind to complement proteins, activating the complement via the classical pathway. Activated compliment can then cause opsonization of bacteria, inflammation, cytolysis via membrane attack complexes, or the elimination of immune complexes by binding them to erythrocytes. 19. Cell-mediated immunity involves T-lymphocyte activation with antigen-presenting cells. Humoral immunity involves Blymphocytes, which do not require APCs . 20. Secondary responses have a much shorter lag phase, with antibody production rising very quickly, when compared to a primary response. During secondary responses the pathogen is typically eliminated even before disease symptoms develop.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Inflammation is a generalized, local response to damage, a toxin, or an infection. It is characterized by the release of fluid into the tissue. 2. A Feedback: The function of a vaccine is to stimulate the immune system to develop memory B-lymphocytes, while providing a relatively safe means for the initial exposure to a microorganism. 3. B Feedback: HIV infects and destroys helper T-lymphocytes over a period of time. Prolonged HIV infection leads to acquired immunodeficiency syndrome (AIDS). 4. D Feedback: Humoral immunity is the production of antibodies, a process mediated by B-lymphocytes. 5. C Feedback: Cell-mediated immunity does not utilize antibodies to target the cells of pathogens or pathogen-infected cells. Humoral immunity utilizes antibodies which are capable of targeting subcellular structures such as viruses.

Answers to “Can You Synthesize What You’ve Learned?” 1. Damage to a tissue may result from chronic irritation. This will result in the release of inflammatory and chemotactic factors from damaged cells. This is followed by vasodilation and increased capillary permeability at the site, producing excessive interstitial fluid. The additional fluid helps to remove cellular debris into the lymphatic system. The pressure caused by the increase in fluid in the area is causing Dianne’s pain. 2. A fever inhibits reproduction of bacteria and viruses, promotes interferon activity, increases activity of adaptive immunity, and accelerates tissue repair. 3. Numerous components of innate immunity provide physical barriers to infection. (1) The epidermis of the skin and the epithelium of mucous membranes provide physical barriers to infection. (2) The normal flora on the skin and in the digestive tract prevent colonization by pathogenic bacteria. Structures such as cilia, vibrissae, or physical processes such as coughing, sneezing, vomiting, or defecation move pathogens out of hollow organs. Secretions such as sebum, sweat, mucus, saliva, HCl, urine, lactic acid, lysozyme, defensins, dermicidin, immunoglobulin A, lacrimal fluid, and cerum also block entry of pathogens into tissues.

Chapter 23 Answers to “What Did You Learn?” 1. Alveoli are associated with the exchange of respiratory gases. 2. The nose, nasal cavity, and pharynx form the upper respiratory tract. The larynx, trachea, bronchi, bronchioles, alveolar ducts, and alveoli are components of the lower respiratory tract. 3. The epithelium of the upper respiratory tract is lined with pseudostratified ciliated columnar epithelium. Alveoli are lined with simple squamous epithelium. 4. Air is cleansed, warmed, and humidified as it passes through the nasal cavity. 5. The nasal conchae produce air turbulence in inhaled air. 6. Ducts connect the paranasal sinuses to the nasal cavity. 7. The nasopharynx contains the pharyngeal tonsil. The oropharynx contains the palatine tonsils. The tonsils are composed of lymphatic tissue and help to prevent the spread of infection. 8. During the Valsalva maneuver the epiglottis is closed over the glottis, preventing the escape of air, while the abdominal muscles contract simultaneously. The result is an increase in abdominal pressure. 9. The epiglottis, thyroid cartilage, and cricoid cartilage are all unpaired. 10. The vocal folds consist of elastic vocal ligaments, surrounded by mucous membranes. The vestibular folds are located in between the individual vocal folds and their corresponding sides of the thyroid cartilage. Vocal folds are involved in sound production. Vestibular folds do not produce sound. 11. These C-shaped rings of tracheal cartilage reinforce and provide some rigidity to the tracheal wall to ensure that the trachea remains open at all times, whereas the more flexible trachealis muscle and ligamentous membrane allow for distension during swallowing of food through the esophagus. 12. Bronchi have rings of hyaline cartilage that prevent collapse. Bronchioles have much smaller diameters than bronchi (less than 1 mm2), but lack supportive rings of cartilage. Instead, bronchioles have proportionally thicker smooth muscles than bronchi. 13. The nose, larynx, trachea, and bronchi are supported by cartilage. 14. Nasal hairs keep large pathogens and debris out of the nasal cavity. Mucus traps pathogens and particulates, and also humidifies inspired air. Cilia, sneezing, and coughing expel trapped substances from the respiratory system. Tonsils in the pharynx and macrophages within the respiratory zone destroy pathogens. 15. Air will pass through the nose, nasal cavity, nasopharynx, oropharynx, laryngopharynx, larynx, rimma glottis, trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, respiratory bronchioles, alveolar ducts, and alveoli. 16. Gases will pass through the endothelium of the capillary, then the basement membrane, and finally the type I epithelial cell of the alveoli. 17. Main bronchus and lung, lobar bronchus and lobe, segmental bronchus and bronchiopulmonary segment, terminal bronchiole and lobule. 18. Bronchial arteries provide the lungs with oxygenated blood, and bronchial veins drain the lungs of deoxygenated blood. Some of the blood from the bronchial veins may drain to the pulmonary veins. 19. Serous fluid acts as a lubricant, ensuring the pleural surfaces slide by each other with minimal friction during breathing. 20. A greater intrapulmonary pressure keeps the lungs inflated and prevents collapse of the lung.

21. Autonomic nuclei in the brainstem stimulate the skeletal muscles involved with breathing to contract and relax. The result is a change in thoracic cavity volume, which in turn produces a changing pressure gradient between the lungs and the atmosphere, driving the inhalation and exhalation of air. 22. (1) The diaphragm and internal intercostal muscles contract, increasing the volume of the thoracic cavity, and subsequently decreasing intrapleural pressure. (2) The lungs expand, decreasing intrapulmonary pressure as the alveolar volume increases. (3) As the intrapulmonary pressure decreases below atmospheric pressure, air moves into the lungs. 23. Forced inspiration and expiration require the recruitment of additional muscles to facilitate the movement of a larger volume of air. This requires a greater expenditure of energy. 24. The ventral respiratory group initiates neural impulses for inspiration and expiration. The dorsal respiratory group relays signals from upper motor neurons, which can then adjust the rate of the ventral respiratory group. 25. Either increase in blood PCO2, increase in blood H+, increase in H+ within the CSF, or increase in blood PO2 will increase the respiratory rate. 26. The control of the breathing muscles comes from both autonomic nuclei in the brainstem and somatic nuclei within the cerebral cortex. 27. Resistance to airflow may be caused by (1) a decrease in elasticity of the chest wall and lungs, (2) a change in the bronchial diameter, or (3) the collapse of alveoli. In order to overcome this resistance, the muscles of inspiration must work harder, and a greater amount of the body’s metabolic energy must be spent on breathing. 28. Two breaths require you to overcome the anatomical dead space twice, whereas one long, slow breath provides the opportunity for gas exchange, similar to two quick breaths, but only has to contend with the anatomical dead space once. 29. The inspiratory capacity is equal to the tidal volume plus the inspiratory reserve volume. The functional residual volume is calculated as the expiratory reserve volume plus the residual volume. Vital capacity is the inspiratory capacity plus the end residual volume. Total lung capacity is the inspiratory capacity plus the functional residual capacity. 30. Carbon dioxide has a solubility coefficient 24 times greater than oxygen; therefore, at the same partial pressure, carbon dioxide would be far more soluble than oxygen. 31. Oxygen will diffuse into the blood from the alveoli until the partial pressure reaches equilibrium at 104 mm Hg. Carbon dioxide will diffuse out of the blood, into the alveoli, until the partial pressure reaches equilibrium at 40 mm Hg. 32. Loss of alveoli, fluid accumulation in the lungs, or arteriole vasoconstriction will decrease alveolar gas exchange. Bronchiole dilation will increase alveolar gas exchange. 33. During systemic gas exchange the partial pressure carbon dioxide in the blood increases from 40 to 45 mm Hg. Conversely, the partial pressure of oxygen in the blood decreases from 95 to 40 mm Hg. 34. Because the solubility of oxygen is so low, it must be transported as oxyhemoglobin, bound to hemoglobin in erythrocytes. 35. The majority of carbon dioxide, approximately 70%, is transported through the blood as dissolved bicarbonate ions. 36. (1) During alveolar gas exchange, oxygen diffuses into the blood from alveoli down its concentration gradient. (2) Over 98% of the oxygen is transported as oxyhemoglobin, bound to hemoglobin. Less than 2% of the oxygen is transported while dissolved in blood plasma. (3) During systemic gas exchange oxygen diffuses in from the blood, into tissues down the concentration gradient. 37. (1) During systemic gas exchange carbon dioxide leaves tissue and enters the blood, down the concentration gradient. (2) Then 23% of the carbon dioxide in the blood is transported bound to hemoglobin, as carbaminohemoglobin; 7% of the carbon dioxide is transported dissolved in blood plasma. The majority of carbon dioxide is converted to carbonic acid by carbonic anhydrase, and then spontaneously breaks down to bicarbonate ions as H+, which are readily dissolved in the blood. (3) During alveolar gas exchange, carbonic acid is converted back to carbon dioxide by carbonic anhydrase. Carbon dioxide enters the alveoli from blood down the concentration gradient.

38. The affinity of hemoglobin for oxygen increases with increased PO2. Therefore, as the partial pressure of oxygen in the blood increases with alveolar gas exchange, so does the oxygen saturation of hemoglobin. 39. More oxygen is released from hemoglobin in response to increased temperatures, decreased pH, or increased levels of 2,3-BPG or CO2. Conversely, oxygen-hemoglobin disassociation is inhibited by high PO2. 40. During hyperventilation blood PO2 does not change; however, blood PCO2 drops significantly, causing hypocapnia. 41. During exercise blood PO2 and PCO2 levels stay relatively constant. 42. Breathing changes during exercise may change due to (1) sensory signals relayed from proprioceptors in joints, muscles, and tendons in response to movement; (2) motor output originating in the cerebral cortex that initiates muscular movement during exercise, simultaneously relaying signals to the respiratory center; or (3) the conscious anticipation of participating in exercise.

Answers to “Do You Know the Basics?” 1. D Feedback: Respiration involves gas exchange within the respiratory system, muscle contraction for pulmonary ventilation, and regulation by the nervous system. 2. A Feedback: The lungs are divided into lobes, consisting of isolated segments, which in turn are composed of isolated lobules. Lobules contain alveoli. 3. C Feedback: A greater intrapulmonary pressure keeps the lungs inflated and prevents collapse of the lung. 4. A Feedback: Autonomic nuclei in the brainstem stimulate the skeletal muscles involved with breathing to contract and relax. The result is a change in thoracic cavity volume, which in turn produces changing pressure gradient between the lungs and the atmosphere, driving the inhalation and exhalation of air. 5. B Feedback: Quiet expiration does not involve muscle contraction. 6. C Feedback: The medulla oblongata contains ventral and dorsal respiratory groups. The ventral respiratory group initiates neural impulses for inspiration and expiration. The dorsal respiratory group relays signals from upper motor neurons which originate at the pons, and are capable of adjusting the rate of the ventral respiratory group in response to the needs of the body. 7. B Feedback: Carbon dioxide, and its derivative carbonic acid, trigger chemoreceptors which adjust the respiratory rate. 8. C Feedback: Systemic gas exchange involves the movement of respiratory gases between blood and body tissues. 9. C Feedback: Of the carbon dioxide in the blood, 23% is transported bound to hemoglobin, as carbaminohemoglobin; 7% is dissolved in blood plasma. The majority of carbon dioxide (nearly 70%) is converted to carbonic acid by carbonic anhydrase, and then spontaneously breaks down to bicarbonate ions, an H+, which are readily dissolved in the blood. 10. D Feedback: Upon release of oxygen, hemoglobin becomes less saturated. 11. Air will pass through the nose, nasal cavity, nasopharynx, oropharynx, laryngopharynx, larynx, rimma glottis, trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, respiratory bronchioles, alveolar ducts, and alveoli. 12. The visceral pleura lines the lungs. The parietal pleura lines the inner body wall of the thoracic cavity and diaphragm. The pleural cavity is a potential space located between the visceral and parietal serous membrane layers, and contains serous fluid. During

pulmonary ventilation, the intrapulmonary pressure, inside of the lungs, remains greater than the intrapleural pressure, thereby preventing the lungs from collapsing. 13. The four processes involved in moving oxygen from the atmosphere are (1) pulmonary ventilation, (2) alveolar gas exchange, (3) gas transport in the blood, and (4) systemic gas exchange. The four steps in transport of carbon dioxide from tissues to the atmosphere are (1) systemic gas exchange, (2) gas transport in the blood, (3) alveolar gas exchange, and (4) pulmonary ventilation. 14. For inspiration, (1) the diaphragm and internal intercostal muscles contract, increasing the volume of the thoracic cavity, and subsequently decreasing intrapleural pressure. (2) The lungs expand, decreasing intrapulmonary pressure as the alveolar volume increases. (3) As the intrapulmonary pressure decreases below atmospheric pressure, air moves into the lungs. During exhalation, (4) relaxation of the diaphragm and intercostal muscle decreases the volume of the thoracic cavity, increasing intrapleural pressure, (5) which increases intrapulmonary pressure. (6) As the intrapulmonary pressure increases above atmospheric pressure, air leaves the lungs. 15. Contraction of accessory muscle can increase the volume of the thoracic cavity, above what can be generated by passive breathing. Contraction of abdominal muscles can increase abdominal pressure, which in turn will decrease intrapulmonary volume, expelling additional air from the lungs. 16. Autonomic nuclei of the ventral respiratory group in the medulla oblongata stimulate the skeletal muscles involved with breathing to contract and relax. The result is a change in the thoracic cavity volume, which in turn produces changing pressure gradient between the lungs and the atmosphere, driving the inhalation and exhalation of air. 17. During alveolar gas exchange oxygen enters the blood because the partial pressure of oxygen is greater within alveoli than in blood. Carbon dioxide leaves the blood because its partial pressure is greater in blood than in alveolar air. During systemic gas exchange oxygen leaves the blood because its partial pressure is greater in the blood than in the tissue. Conversely, carbon dioxide leaves the tissue and enters the blood down its own concentration gradient. 18. Over 98% of the oxygen is transported as oxyhemoglobin, bound to hemoglobin; less than 2% of the oxygen is transported while dissolved in blood plasma; 23% of the carbon dioxide in the blood is transported bound to hemoglobin, as carbaminohemoglobin; 7% of the carbon dioxide is transported dissolved in blood plasma. The majority of carbon dioxide (nearly 70%) is converted to carbonic acid by carbonic anhydrase, and then spontaneously breaks down to bicarbonate ions, an H+, which are readily dissolved in the blood. 19. The affinity of hemoglobin for oxygen increases with increased PO2. Conversely, in tissues with low PO2, hemoglobin affinity for oxygen decreases, allowing O2 to be released. 20. Increased temperature, increased concentrations of H+, increased 2,3-BPG, or increased CO2 all decrease the affinity of hemoglobin for oxygen.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: The pons adjust the activity of the ventral respiratory group of the medulla oblongata. 2. D Feedback: Emphysema results from the loss of alveolar surface area. 3. C Feedback: Decreased capacity to ventilate her lungs will require her to engage accessory muscles to ventilate her lungs, thereby expending more energy. 4. A Feedback: Poor ventilation and gas exchange will result in lowered blood PO2, and increased PCO2. The increased PCO2 will lead to respiratory acidosis. 5. B Feedback: Asthma is usually an allergic reaction, leading to inflammation of mucous membranes and bronchoconstriction of bronchioles, which greatly decreases the amount of air able to reach the respiratory zone.

Answers to “Can You Synthesize What You’ve Learned?” 1. Asthma is usually an allergic reaction leading to inflammation of mucous membranes and bronchoconstriction of bronchioles, greatly decreasing the amount of air able to reach the respiratory zone. This would result in lowered blood PO2, and increased PCO2. The primary treatment for asthma consists of administering inhaled steroids to reduce the inflammatory reaction, combined with bronchodilators to alleviate the bronchoconstriction. 2. The sternocleidomastoid participates in expansion of the lungs during forced inspiration. 3. As altitude increases, the PO2 of air decreases, and subsequently alveolar PO2 is lowered. Since the alveolar exchange of oxygen is driven by the PO2 gradient between alveoli and the blood, less O2 will enter the blood, resulting in poor hemoglobin saturation. In response to the drop in blood PO2 the rate of pulmonary ventilation would increase, decreasing blood PCO2, possibly decreasing blood pH, causing respiratory alkalosis. Decreased PO2 also causes vasoconstriction of blood vessels in the brain, depriving the brain of oxygen, which can cause dizziness and fainting.

Chapter 24 Answers to “What Did You Learn?” 1. The kidneys form urine. The urinary bladder stores urine. 2. The kidneys can regulate blood pressure by adjusting the retention of water in the kidney, or by causing systemic vasoconstriction. 3. The kidney is surrounded by a fibrous capsule, which is surrounded by a layer of perinephric fat. Renal fascia surrounds the perinephric fat. The entire structure is surrounded by a superficial layer of paranephric fat. 4. Urine drains through the minor calyces, major calyces, and renal pelvis of the kidney. 5. The sympathetic branch of the autonomic system stimulates afferent arterioles, efferent arterioles, and the juxtaglomerular apparatus in the kidneys. 6. The renal corpuscle consists of a thick tangle of capillaries called the glomerulus, and glomerular capsule. The capsule consists of a parietal layer of simple squamous epithelium, and a visceral layer of podocytes covering the glomerulus. 7. The renal tubule consists of the proximal convoluted tubule, the thick segment of the descending limb of the nephron loop, the ascending limb of the nephron loop, and the distal convoluted tubule. 8. Cortical nephrons are oriented with their renal corpuscles near the peripheral edge of the cortex and have a relatively short nephron loop that barely penetrates the medulla. Juxtamedullary nephrons have a renal corpuscle adjacent to the corticomedullary junction, and they have relatively long nephron loops that extend deep into the medulla. 9. Intercalated cells help regulate urine pH and blood pH. 10. The granular cells of the juxtamedullary apparatus are stimulated by either stretch or innervation by the sympathetic branch of the autonomic nervous system. Cells of the macula densa respond to changes in NaCl concentrations in filtrate within the distal convoluted tubule. 11. Blood flows from the (1) renal artery to the (2) segmental artery, (3) lobar artery, (4) interlobar artery, (5) arcuate artery, (6) interlobular artery, (7) afferent arteriole, (8) glomerulus, (9) efferent arteriole, (10) either peritubular capillaries or vasa recta, (11) interlobular veins, (12) arcuate vein, (13) interlobar vein, and (14) renal vein. 12. The glomerulus is responsible for filtration within the renal corpuscle. The peritubular capillaries participate in reabsorption in most nephrons. The vasa recta facilitates in reabsorption in juxtamedullary nephrons. 13. From the (1) capsular space, tubular fluid passes through the (2) proximal convoluted tubule, (3) descending limb of the loop of Henle, (4) ascending limb of the loop of Henle, (5) distal convoluted tubule, (6) collecting tubules, and (7) collecting duct. After this point, it is referred to as urine, which continues on through the (8) papillary duct, (9) minor calyces, (10) major calyces, (11) renal pelvis, (12) ureter, (13) urinary bladder, and finally (14) the urethra. 14. Tubular reabsorption occurs when components within the tubular fluid move out from the lumen of the renal tubules, collecting tubules, and collecting ducts and return to the blood within the peritubular capillaries and vasa recta. Tubular secretion is the movement of solutes out of the blood into the tubular fluid. 15. The filtration membrane is composed of three layers. The basement membrane of the capillary surrounds the endothelium. Podocytes sit on top of the basement membrane, forming the visceral layer of the glomerular capsule. Filtration slits formed by foot processes of podocytes, negative charge within the basement membrane, and fenestrations within the endothelium regulate filtration at the glomerulus. 16. Small substances such as water, glucose, amino acids, ions, some hormones, vitamins B and C, and ketones can pass easily through the filtration membrane, whereas formed elements and large proteins cannot. 17. Loss of charge at the filtration membrane would permit protein to enter the filtrate. 18.

NFP = HPg – (OPg + HPc) NFP = 65 mm Hg – (30 mm Hg – 20 mm Hg) NFP = 55 mm Hg

19.

The net filtration pressure would increase, since: NFP = HPg – (OPg + HPc) NFP = 75 mm Hg – (30 mm Hg – 20 mm Hg) NFP = 65 mm Hg

20. There is a direct relationship between the net filtration pressure and glomerular hydrostatic pressure. NFP increases as HPg increases. 21. Urine production increases with increased glomerular filtration. 22. Renal autoregulation maintains GFR by altering the size of the afferent arteriole in response to changes in systemic blood pressure. Stimulation by the sympathetic division of the autonomic nervous system, and the subsequent production of angiotensin II, decrease GFR by causing vasoconstriction of afferent arterioles and contraction of mesangial. Atrial natriuretic peptide increases GFR through vasodilation of the afferent arteriole, inhibition of renin release, and the subsequent relaxation of mesangial cells. 23. A person with blood pressure of 300/150 mm Hg would have a mean arterial pressure of 200 mm Hg. A person with blood pressure of 70/55 mm Hg would have a mean arterial pressure of 60 mm Hg. Both values are outside of the range manageable through renal autoregulation. 24. In order to be reabsorbed or secreted, substances must be able to move across the simple epithelium of the renal tubule, either by paracellular or trancellular transport. During transcellular transport, a substance must cross two separate membranes, a luminal membrane and a basement membrane, and the correct transport proteins must be present in sufficient quantities. Finally, peritubular colloid pressure is required for reabsorption out of substances from the interstitial fluid surrounding the renal tubule. 25. The transport maximum is the maximum amount of a substance that can be reabsorbed (or secreted) across the tubule epithelium in a given period of time. This is dependent upon the number of the transport proteins in the epithelial cell membrane specific for the substance. This is different from the renal threshold, which is the maximum plasma concentration of a substance that can be carried in the blood without eventually appearing in the urine. 26. Glucose is first transported into the tubule cell across the luminal membrane by a Na+/glucose symporter. Energy from Na+ moving down its concentration gradient into the tubule cell is used to move glucose up its concentration gradient into the tubule cell by secondary active transport. Glucose is then moved by glucose uniporters out of the tubule cell down its concentration gradient via facilitated diffusion across the basolateral membrane. 27. Proteins are metabolized into individual amino acids during reabsorption from renal tubules. The intact protein is never “reabsorbed”; however, it is transported incrementally back into the blood. 28. Sodium reabsorption occurs along the entire length of the renal tubule. A Na+/K+ pump moves sodium out of tubular cells, into the interstitial space, creating a Na+ gradient. Since the sodium concentration is greater in tubular fluid than the tubular cells, it will diffuse down the gradient into tubular cells, and then out through the basal membrane into the interstitial fluid. Aldosterone will increase reabsorption of sodium by increasing the number of sodium channels and pumps available to the tubular cell. Atrial natriuretic peptide, which inhibits the release of aldosterone, decreases sodium reabsorption. The reabsorption of water from renal tubules is tied to the movement of sodium. Water follows sodium out of the tubular fluid by osmosis; therefore, increasing the amount of sodium reabsorbed will increase water reabsorption. Decreasing the amount of sodium reabsorbed will decrease water reabsorption. 29. Parathyroid hormone inhibits PO43- reabsorption in the proximal convoluted tubule, and stimulates reabsorption of Ca2+ in the distal convoluted tubule. 30. Type A intercalated cells secrete H+ and reabsorb HCO3− to raise blood pH and decrease urine pH. Conversely, type B intercalated cells secrete HCO3− and reabsorb H+ to lower blood pH and increase urine pH. 31. The kidneys eliminate wastes such as urea, uric acid, and creatinine, bilirubin, hormone metabolites, hCG, epinephrine, and norepinephrine. 32. The countercurrent multiplier system along the nephron loop establishes a sodium gradient necessary to drive the reabsorption of water. The descending limb of the loop is permeable to water, but not to salt. The ascending limb is impermeable to water, but actively pumps sodium out of the loop into the interstitial fluid. As fluid flows down the descending limb, water is drawn out. The fluid that remains in the tubule and enters the ascending limb is far more concentrated, allowing more sodium to be pumped out, thereby increasing the effect on the descending limb.

33. The proximal convoluted tubule reabsorbs 100% of nutrients, and most of the water and ions. It also secretes some drugs and nitrogenous waste products. The nephron loop reabsorbs water. The distal convoluted tubule reabsorbs sodium, water, potassium, calcium, bicarbonate, and protons. The collecting duct is responsible for the reabsorption of urea. 34. The glomerular filtration rate is an indicator of renal function. 35. It is important to determine renal plasma clearance to know the amount and timing of drug dosage. The higher the renal plasma clearance, the more often the medications must be given to maintain therapeutic levels. 36. Urine characteristics include its composition, volume, pH, specific gravity, color and turbidity, and smell. The pH of urine may be affected by diet, metabolism, or bacterial infections. 37. The ureters consist of a mucosa, muscularis, and adventitia. The urinary bladder consists of the mucosa, submucosa, muscularis, and adventitia. 38. The male urethra is longer and has both reproductive and urinary functions. The female urethra is significantly shorter, and is not part of the reproductive tract. The entire length of the female urethra is lined with stratified squamous epithelium. In the male, the prostatic urethra is lined with transitional epithelium, the membranous urethra and proximal portions of the spongy urethra is lined with stratified columnar epithelium, and the distal portion of the spongy urethra is lined with stratified squamous epithelium. 39. (1) Distention of the bladder wall triggers baroreceptors. (2) Baroreceptors trigger the micturition reflex center within the pons. (3) The micturition center fires parasympathetic nerves to the bladder. (4) Parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax. (5) Voluntary relaxation of the external urethral sphincter along with Valsalva maneuver allows micturition. Urination may occur without conscious control once the bladder contains 500–600 mL of urine.

Answers to “Do You Know the Basics?” 1. D Feedback: The kidneys regulate blood volume by reabsorbing water. 2. B Feedback: The kidneys are located within the abdominal cavity, posterior to the peritoneum. 3. A Feedback: Collecting ducts and nephron loops are present in the renal medulla. 4. B Feedback: The minor calyx is part of drainage for collecting urine. It is not a blood vessel. 5. D Feedback: Under normal conditions, 100% of glucose is reabsorbed in the proximal convoluted tubule. 6. C Feedback: There is a direct relationship between glomerular filtration and urine production. Increased glomerular filtration causes increased urine production. 7. D Feedback: Aldosterone increases sodium reabsorption. Sodium reabsorption is directly related to water reabsorption and inversely related to potassium reabsorption. 8. C Feedback: If the concentration of a substance overwhelms the capacity for its reabsorption, it will eventually appear in the urine. 9. C Feedback: The loop of Henle establishes the sodium concentration gradient within the renal medulla through the countercurrent multiplier system. 10. C Feedback: ADH stimulates the reabsorption of water from tubular fluid, decreasing urine volume, and increasing urine concentration.

11. Blood flows from the (1) renal artery to the (2) segmental artery, (3) lobar artery, (4) interlobar artery, (5) arcuate artery, (6) interlobular artery, (7) afferent arteriole, (8) glomerulus, (9) efferent arteriole, (10) either peritubular capillaries or vasa recta, (11) interlobular veins, (12) arcuate vein, (13) interlobar vein, and (14) renal vein. 12. Filtrate is present in the capsular space. It is referred to as tubular fluid in the proximal convoluted tubule, nephron loop, distal convoluted tubule, collecting tubule, and collecting duct. Urine is present in the papillary duct of the kidney. 13. Granular cells are modified smooth muscle cells of the afferent arteriole located near its entrance into the renal corpuscle. The macula densa is a group of modified epithelial cells in the wall of the distal convoluted tubule where it contacts the granular cells. The cells of the macula densa are located only on the tubule side next to the afferent arteriole, and they are narrower and taller than other distal convoluted tubule epithelial cells. 14. The filtration membrane is composed of three layers. The basement membrane of the capillary surrounds the endothelium. Podocytes sit on top of the basement membrane forming the visceral layer of the glomerular capsule. Filtration slits are formed by foot processes of podocytes, negative charge within the basement membrane, and fenestrations within the endothelium regulate filtration at the glomerulus. Formed elements and most large proteins do not normally cross the filtration membrane. 15. Renal autoregulation maintains GFR by altering the size of the afferent arteriole in response to changes in systemic blood pressure. Stimulation by the sympathetic division of the autonomic nervous system, and the subsequent production of angiotensin II, decreases GFR by causing vasoconstriction of afferent arterioles and contraction of mesangial. Atrial natriuretic peptide increases GFR through vasodilation of the afferent arteriole, inhibition of renin releases, and the subsequent relaxation of mesangial cells. 16. Aldosterone induces principal cells to synthesis of Na+ channels and Na+/K+ pumps, increasing the sodium gradient necessary for water reabsorption from tubular fluid. Antidiuretic hormone increases water reabsorption from the filtrate by stimulating the insertion of aquaporin channels into the membranes of principle cells, facilitating increased water reabsorption, and a subsequent smaller volume of more concentrated urine. A decrease in ADH results in an increase in urine volume that is less concentrated. 17. The countercurrent multiplier system along the nephron loop establishes a sodium gradient necessary to drive the reabsorption of water. The descending limb of the loop is permeable to water, but not to salt. The ascending limb is impermeable to water, but actively pumps sodium out of the loop into the interstitial fluid. As fluid flows down the descending limb, water is drawn out. The fluid remaining in the tubule enters the ascending limb and is far more concentrated, allowing more sodium to be pumped out, thereby increasing the effect on the descending limb. 18. Filtrate and urine usually lack formed elements and proteins. Blood plasma and filtrate may contain large amounts of nutrients, sodium, and bicarbonate. By the time urine is produced, most bicarbonate and nutrients have been reabsorbed. 19. Kidneys are responsible to (a) maintain blood pH; (b) regulate blood ion concentrations; (c) regulate blood volume and blood pressure; (d) eliminate wastes, some hormones, and certain drugs from the blood; (e) release renin; (f) and release erythropoietin. The kidneys do not stimulate the final step in calcitriol formation. 20. (1) Distention of the bladder wall triggers baroreceptors. (2) Baroreceptors trigger the micturition reflex center within the pons. (3) The micturition center fires parasympathetic nerves to the bladder. (4) Parasympathetic stimulation causes detrusor muscles to contract and the internal urethral sphincter to relax. (5) Voluntary relaxation of the external urethral sphincter along with Valsalva maneuver allow micturition.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Her elevated blood pressure will increase glomerular filtration, overwhelming renal autoregulation mechanisms. 2. C Feedback: Plasma protein levels will decrease as they are lost in urine. 3. B Feedback: Excess protein in tubular fluid will create an oncotic gradient that counteracts water reabsorption, resulting in decreased water reabsorption, and increased urine production. 4. A Feedback: Glomerular blood pressure is directly related to systemic blood pressure. As systemic blood pressure drops, so does the GFR. A drop in GFR will cause a drop in urine production.

5. D Feedback: Severing the spinal cord will inhibit conscious control over micturition. It will not affect the reflexive mechanisms of emptying the bladder upon distention. Therefore, incontinence may result.

Answers to “Can You Synthesize What You’ve Learned?” 1. High renal clearance means that the drug is removed quickly from the patient’s bloodstream. It will need to be administered more often. 2. Atrial natriuretic peptide inhibits both the reabsorption of Na+ in the proximal convoluted tubule and collecting tubules and the release of aldosterone. Consequently, more Na+ and water are excreted in urine, reducing blood volume. 3. The prostatic urethra passes through the prostate gland. Enlargement of the prostate gland will put pressure on the urethra, occluding it and preventing micturition.

Chapter 25 Answers to “What Did You Learn?” 1. Increased adipose will decrease the percentage of body fluid. 2. Potassium, magnesium, and phosphates are prevalent in intracellular fluid. Sodium, bicarbonate, and chloride are more prevalent in extracellular fluid. 3. Blood plasma contains blood proteins and formed elements. 4. When you are dehydrated, the net movement of water is from cell into blood plasma. 5. Preformed water from diet, and metabolic water comprise the total water intake. Fluid may be lost through breathing, sweating, cutaneous transpiration, defecation, and urination. Urine production is dependent upon the state of hydration of the body. 6. Both volume depletion (deficiency) and dehydration will result in fluid loss. Depletion is isotonic, whereas dehydration may lead to changes in osmolality; consequently, depletion does not cause the movement of water in between compartments like dehydration. 7. Decreased salivary secretions, increased blood osmolarity, and decreased blood pressure stimulate an increase in thirst. 8. Angiotensin II and atrial natriuretic peptide increase urine output. 9. Electrolytes can dissociate into constituent ions, and therefore contribute more to the osmotic pressure. 10. Decreased pH will cause a net efflux of potassium ions from cells. As protons move into the cell to balance the excess of protons in the ECF, potassium ions move out of the cell to prevent an electrostatic gradient. 11. Angiotensin II causes vasoconstriction, decreasing glomerular hydrostatic pressure and subsequently decreasing the glomerular filtration rate. Decreased GFR leads to decreased urine production. Angiotensin II also induces the release of aldosterone from the adrenal cortex, facilitating the retention of sodium in the kidneys and, subsequently, the retention of water. Lastly, angiotensin II stimulates thirst centers in the hypothalamus, inducing the uptake of water. 12. The release of ADH from the hypothalamus is stimulated by either; angiotensin II, by baroreceptors in the atria of the heart or carotid bodies detecting a drop in blood pressure, or by chemoreceptors within the hypothalamus detecting decreasing blood osmolarity. ADH causes a sensation of thirst, increased reabsorption of water in the kidneys, and vasoconstriction. 13. Low blood pressure and changes in Na+ and K+ blood plasma levels cause aldosterone release. Blood volume and blood pressure are maintained through the reabsorption of both Na+ and water in the kidneys. 14. ANP decreases fluid output from the kidneys, thereby increasing blood volume and systemic blood pressure. 15. The acid-base balance is the regulation of hydrogen ion concentration in body fluids in order to maintain an arterial blood pH between 7.35 and 7.45. 16. Fixed acids are products of metabolism such as fatty acids and ketone bodies. Volatile acid is carbonic acid, produced by transport of carbon dioxide from cellular respiration. 17. The kidneys respond to metabolic acids by reabsorbing all filtered HCO3– along the length of the nephron, synthesizing and absorbing new HCO3–, and excreting H+ into the filtrate. 18. During hyperventilation, blood CO2 levels decrease, causing the H+ concentration in the blood to decrease, and increasing the pH. 19. The protein buffering system buffers within cells and in blood plasma. The phosphate buffering system buffers intracellular fluid. The bicarbonate buffer system buffers blood and extracellular fluid. 20. The chemical buffering system is quick to respond (within seconds); however, it has a limited buffering capacity. Under normal conditions, chemical buffers provide adequate buffering, until the respiratory system is able to adjust conditions accordingly (within minutes). The urinary system provides long-term buffering (hours or days), especially for metabolic acids.

21. An acid-base imbalance that can be compensated by the body's buffering mechanisms is referred to as being compensated. An uncompensated acid-base imbalance overwhelms the body’s ability to regulate acid-base balance. 22. During hyperventilation, blood CO2 levels decrease due to rapid exhalation, causing the H+ concentration in the blood to decrease, and increasing the pH. 23. Metabolic acidosis occurs when arterial blood levels of bicarbonate fall below normal due to the production of excessive metabolic acids, decreased illumination of acids due to renal dysfunction, or increased elimination of bicarbonate as a result of severe diarrhea. 24. Renal compensation results in elevated values for blood HCO3– due to the excretion of higher than normal levels of H+, and reabsorption of higher than normal amounts of HCO3– into the blood. During respiratory compensation, higher than normal amounts of CO2 are expired, lowering blood PCO2.

Answers to “Do You Know the Basics?” 1. D Feedback: The percentage of body water increases with lean muscle mass. 2. A Feedback: Two thirds of body fluids are located within cells. 3. B Feedback: Increased hydrostatic pressure drives fluid out of blood, into tissues. 4. B Feedback: Decreased saliva production, increased blood osmotic pressure, decreased blood volume, and decreased blood pressure are symptoms of dehydration. 5. C Feedback: ANP decreases fluid output from the kidneys, thereby increasing blood volume and systemic blood pressure. 6. D Feedback: Electrolytes contribute to the osmolality of blood, and consequently affect the regulation of fluid balance. 7. C Feedback: Sodium is actively maintained at high concentrations within the ECF throughout the body, in order to maintain osmotic pressure. 8. D Feedback: Carbon dioxide forms carbonic acid in blood, which disassociates into hydrogen ions and bicarbonate, lowering the pH of blood. 9. A Feedback: Carbohydrates do not serve as buffers. 10. D Feedback: The kidneys are capable of secreting or reabsorbing hydrogen ions, as well as producing bicarbonate in order to buffer blood. 11. The body’s fluid composition depends upon age, sex, and the relative amounts of adipose and skeletal muscle tissue. 12. Water will move from the digestive system into the hypertonic solution of the blood. It will then move to the relatively hypertonic interstitial spaces and cells. 13. Decreased saliva production, increased blood osmolarity, and decreased blood pressure induce the sensation of thirst. Increased saliva production, distention of the stomach, decreased blood osmolarity, or increased blood pressure cause a decrease in the sensation of thirst.

14. Renin is released from granular cells of the juxtaglomerular apparatus, in response to decreased blood flow to the kidney. Renin converts angiotensinogen to angiotensin I, which is in turn converted to its active form, angiotensin II. Angiotensin II increases systemic blood pressure by causing vasoconstriction, and also induces the release of ADH from the hypothalamus, and the release of aldosterone from the adrenal cortex. ADH and aldosterone increase water reabsorption in the kidney, which increases blood pressure. 15. Atrial natriuretic peptide is released in response to increased stretch in atria as a consequence of high blood volume and high blood pressure. ANP causes systemic vasodilation, decreased GFR, decreased sodium and water retention in the kidneys, and a subsequent drop in blood pressure. Decreased blood pressure inhibits the release of renin, which is responsible for the release of aldosterone and ADH. 16. Sodium is an important factor in establishing the osmolarity of blood. Aldosterone induces the reabsorption of Na+ in the kidneys, ADH causes the reabsorption of water in the kidneys, which decreases the overall concentration of Na+ in the blood, and ANP decreases Na+ retention in the kidneys. 17. In response to an increase in blood plasma H+ concentrations, type A intercalated cells in the kidneys secrete H+ into tubular fluid and reabsorb HCO3− to raise blood pH. 18. During hyperventilation, blood CO2 levels decrease, causing the H+ concentration in the blood to decrease, and increasing the pH. 19. The protein buffering system buffers within cells and in blood plasma. The amine groups of a peptide act as weak bases and the carboxylic acid groups act as weak acids. The phosphate buffering system buffers intracellular fluid. Phosphates are abundant intracellular ions that can form either H2PO4− (a weak acid) or HPO42- (a weak base), in an aqueous environment. The bicarbonate buffer system buffers blood and extracellular fluid. In an aqueous environment, H2CO3 (a weak acid) can disassociate into bicarbonate HCO3− (a weak base). 20. In respiratory acidosis, respiratory rate decreases and blood CO2 increases, producing increased carbonic acid. The kidneys compensate with increased secretion of H+ and increased reabsorption of HCO3–. The increase in blood HCO3– from renal compensation reestablishes acid-base balance.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Vomiting, diarrhea, and decreased water intake all cause dehydration. 2. B Feedback: Extracellular K+ levels are usually very low. Upon damage to cells, K+ was released from ICF, raising levels in the ECF. 3. D Feedback: Water is a hypotonic to blood plasma. Drinking water without supplementing electrolytes will cause an osmotic imbalance. The kidneys will compensate by increasing urine production, in essence, negating the effects of drinking fluids. 4. B Feedback: Ketoacidosis is a metabolic disorder associated with an imbalance between lipid anabolism and lipid catabolism, often due to decreased production or sensitivity to insulin. 5. A Feedback: Due to the presence of metabolic acids, his bloodwork would indicate metabolic acidosis, with respiratory compensation.

Answers to “Can You Synthesize What You’ve Learned?” 1. Aldosterone causes the retention of Na+ and secretion of K+ ions in the kidneys. 2. The high level of CO2 in the blood would indicate respiratory acidosis. The high level of bicarbonate is a product of the kidneys compensating for the pH imbalance in the blood. The pH of her blood is within the normal range, hence compensation is adequate.

Chapter 26 Answers to “What Did You Learn?” 1. Chemical digestion breaks covalent bonds between monomers of nutrient polymers. 2. The gastrointestinal tract forms a continuous tube along which digestion occurs. Accessory organs facilitate processes of digestion that occur within the GI tract. 3. Substances must cross the epithelium of the mucosa before being absorbed into the blood or lymph. 4. A sphincter closes off the lumen at some point along the GI tract, and in so doing it can control the movement of materials into the next section of the GI tract. 5. Mixing is a back-and-forth motion, localized in one region of the gastrointestinal tract. Peristalsis propels substances along the GI tract. 6. Intraperitoneal organs are completely surrounded by visceral peritoneum. They include the stomach, most of the small intestine, and parts of the large intestine. Retroperitoneal organs lie directly against the posterior abdominal wall, so only their anterolateral portions are covered with peritoneum. 7. The greater omentum extends inferiorly from the greater curvature of the stomach and covers most of the abdominal organs. 8. Long reflexes involve interaction through the autonomic branch of the central nervous system. 9. Gastrin, secretin, and cholecystokinin are the three primary hormones that regulate the digestive processes. 10. The oral cavity, salivary glands, pharynx, esophagus, and stomach comprise the upper gastrointestinal tract. 11. Saliva moistens food and begins the digestion of complex carbohydrates. Teeth break food apart into smaller pieces, which are easier to swallow. The tongue manipulates food in the mouth and initiates swallowing. 12. The mucosa of the esophagus contains stratified squamous rather than simple columnar epithelium. The muscularis layer also differs in that it contains skeletal muscle. The proximal third of the esophageal muscularis consists of skeletal muscle, the distal third contains smooth muscle, and the intermediate third contain a mix of both skeletal and smooth muscles within the muscularis. 13. In the voluntary phase of swallowing, the bolus of food is pushed by tongue against hard palate and then moves toward the oropharynx. During the pharyngeal phase the soft palate and uvula close off nasopharynx, and the larynx elevates, causing the epiglottis to close over the laryngeal opening. During the esophageal phase, peristaltic contractions of esophageal muscle push bolus toward stomach. 14. Mucous cells produce mucus to protect and lubricate the mucosa. Surface mucous cells produce an alkaline mucin, whereas as mucous neck cells produce a more acidic mucin. Parietal cells produce intrinsic factor which is involved in absorption of vitamin B12 in the small intestines. They also produce hydrochloric acid, which helps with the activation of pepsinogen, denatures proteins, and protects the alimentary canal from pathogens. Chief cells release pepsinogen, an inactive zymogen of the protease pepsin. G-cells release gastrin, an endocrine hormone that regulates gastric secretions and motility. 15. The gastric reflex is initiated as food enters the stomach. It is characterized by an increase in gastric motility and an increase in gastric secretions. 16. The small and large intestines comprise the organs of the lower gastrointestinal tract. 17. Circular folds of the mucosa and submucosa line the lumen of the small intestines. Villi are fingerlike projections that are formed along the mucosa extension of the muscularis mucosae. Microvilli are projections of the apical domain of the plasma membrane of epithelial cells lining the small intestines. 18. Segmentation mixes chyme with secretions in the small intestines. 19. Arterial blood and blood from the hepatic portal vein merge at the sinusoids of the liver lobules. 20. The liver produces bile, which helps in the digestion of lipids.

21. Pancreatic juice contains water, bicarbonate ions, and a mix of digestive enzymes. The bicarbonate provides protection by neutralizing acid from the stomach. The digestive enzymes include amylase to digest carbohydrates, lipase to digest lipids, several inactive proteases that when activated, digest proteins, as well as nucleases to digest nucleic acids. 22. Chyme will enter the cecum. From there it will travel through the ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon, rectum, and then out through the anal canal. 23. The indigenous microbiota of the large intestines are responsible for the chemical breakdown of complex carbohydrates, proteins, and lipids that remain in the chyme after it has passed through the small intestine. Bacteria also produce B vitamins and vitamin K, which are absorbed into the blood. 24. The large intestine absorbs water and electrolytes. 25. Starch catabolism begins in the mouth with salivary amylase. Pancreatic amylase from digestive juices released into the small intestines by the pancreas further digests carbohydrates into oligosaccharides, maltose, and glucose. Brush border enzymes then finish the catabolic processes; the enzymes dextrinase and glucoamylase digest oligosaccharides into maltose and glucose, maltase digests the disaccharides maltose into glucose monomers, lactase digests lactose into glucose and galactose, and sucrase digests sucrose into glucose and fructose. 26. Pepsinogen is released from chief cells of the gastric mucosa, and is then activated by the low pH in the stomach into pepsin. Trypsinogen, released from the pancreas, is converted to its active form by enteropeptidase. Trypsinogen then activates the protease zymogens chymotrypsinogen into chymotrypsin, and procarboxypeptidase into caboxypeptidase. This mechanism of storing protease zymogens is necessary in order to protect cells from digestion by their own enzymes. 27. Bile salts emulsify lipids. This is a form of mechanical, not chemical, digestion. 28. Nucleic acid digestion occurs in the small intestines.

Answers to “Do You Know the Basics?” 1. A Feedback: The liver occupies most of the upper left quadrant of the abdomen. 2. B Feedback: Parietal cells release HCl and intrinsic factor in the stomach. 3. B Feedback: Motility and release of hormones are highly regulated in the intestines. Absorption is not regulated by feedback mechanisms. 4. C Feedback: Retroperitoneal digestive organs include most of the duodenum, the pancreas, ascending and descending colon, and the rectum. 5. A Feedback: Pancreatic juice contains bicarbonate from the pancreatic ducts and digestive enzymes from pancreatic acini. 6. C Feedback: The cystic duct is part of the biliary apparatus, which transports bile. 7. B Feedback: Protein digestion begins with pepsin in the stomach. 8. B Feedback: Micelles facilitates the transport, and subsequent hydrolysis, of hydrophobic lipids, in an aqueous environment. 9. C Feedback: Most digestive enzymes, with the exception of salivary amylase, pepsin, and brush border enzymes, are produced in the pancreas and released as part of the pancreatic juice.

10. C Feedback: With the exception of some complex carbohydrate digestion in the mouth, and some protein digestion in the stomach, most digestion occurs in the small intestines. 11. The GI tract consists of four layers: a mucosa lining the lumen, a subucosa, a muscularis layer, and an outer covering of either serosa or adventitia. The mucosa is comprised of epithelium, with an underlying subendoethelial layer of connective tissue, and a layer of smooth muscle called the muscularis mucosae. Throughout the intestines the mucosa is lined with simple columnar epithelium, except in the esophagus, where it is lined with stratified squamous epithelium. The submucosa consists of dense irregular connective tissue and contains numerous glands and components of the enteric nervous system. The muscularis layer contains two rings of smooth muscle, a circular layer and an outer longitudinal layer. A third oblique layer of smooth muscle is present in the muscularis of the stomach. Most of the GI tract is covered with a serous membrane, the peritoneum. An exception is the esophagus, which is surrounded by adventitia. 12. The two layers of skeletal muscle in the superior one-third of the esophageal muscularis ensure that the swallowed material moves rapidly out of the pharynx and into the esophagus before the next respiratory cycle begins. 13. The pancreas produces three separate proteases; therefore, proteolysis by pepsin is not critical for digestion of proteins. Parietal cells of the stomach are the only place where intrinsic factor is produced. 14. Circular folds of the mucosa and submucosa line the lumen of the small intestines. Villi are fingerlike projections formed along the mucosa extension of the muscularis mucosae. Microvilli are projections of the apical domain of the plasma membrane of epithelial cells lining the small intestines. 15. Abundant mucus is critical for protection of the walls of the large intestine due to abrasion from compacted fecal matter. 16. Proteases are stored and released as zymogens, in order to protect the cells that produce them from digestion by their own enzymes. 17. The gallbladder stores and concentrates bile. 18. Mastication by teeth breaks food into manageable pieces for swallowing. Segmentation in the stomach mixes the bolus with digestive enzymes and HCl, breaking it up into even smaller pieces, which make up chyme. Bile salts emulsify lipids in the small intestines, facilitating their digestion by lipase. 19. Hydrochloric acid denatures proteins and activates pepsinogen. The active form of pepsinogen, pepsin, is a protease which then severs covalent peptide bonds between specific amino acid residues. 20. Digested fats and lipids are transported through the aqueous chyme surrounded by micelles. As the lipids are brought across the apical membranes of cells lining the mucosa, they are stripped of micelles, which remain in the lumen. Within the epithelial cells, the lipids are wrapped in proteins to form chylomicrons by the Golgi apparatus, and released basolaterally from the cells by exocytosis. Once in the interstitial fluid, they are picked up by lacteals and delivered by the lymphatic system to the vena cava.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: The one critical function of the stomach is the production of intrinsic factor. Intrinsic factor is critical for the absorption of vitamin B12 in the small intestines. 2. B Feedback: The gallbladder stores and concentrates bile, which is critical for lipid digestion. Without the capacity to concentrate bile, he will not be able to process large amounts of fats at one time. 3. A Feedback: The small intestine is responsible for the digestion and absorption of nearly all nutrients. 4. C Feedback: The pancreatic ducts release bicarbonate and digestive enzymes from the pancreas into the small intestine.

5. A Feedback: Appendicitis results from a bacterial infection in the vermiform appendix. Rupture of the appendix releases these pathogens in the abdominal cavity.

Answers to “Can You Synthesize What You’ve Learned?” 1. Vomiting expels gastric contents through the oral cavity. Diarrhea expels the contents of the large intestine rectally. In response to an infection the gastrointestinal tract attempts to expel pathogens by either reversing the effects of peristalsis, which leads to vomiting, or by flooding the colon with water, diluting feces, and resulting in diarrhea. 2. HCl is not produced in parietal cells; rather it is produced by parietal cells. Water is split within the parietal cells. The hydroxyl ions combine with carbon dioxide to form bicarbonate ions, which are transported to the blood through the basolateral domain of the plasma membrane. Meanwhile, the protons are pumped out of the parietal cell by the H+, K+ ATPase. In the lumen of the stomach the protons combine with chloride ions, forming hydrochloric acid. 3. Absorption of fluids, and the subsequent compaction of feces, occurs along the length of the large intestines. During this time the mucosa of the large intestines is exposed to toxins in the forming feces. The distal portion of the colon is exposed to toxins in the fecal matter for longer periods of time, increasing the probability of causing polyps or colorectal cancer.

Chapter 27 Answers to “What Did You Learn?” 1. Nutrient biomolecules include carbohydrates, amino acids, and nucleic acids. 2. Nonessential amino acids can be made in the body. Essential amino acids must come from the diet. 3. B-complex vitamins and vitamin C are water-soluble. Vitamins A, D, E, and K are fat-soluble. If dietary intake of fat-soluble vitamins exceeds body requirements, the excess is stored within the body fat and may reach toxic levels. 4. Major minerals are needed at levels greater than 100 milligrams per day, and trace minerals are required at less than 100 milligrams per day. Major minerals include calcium, chlorine, cobalt, magnesium, manganese, phosphorus, potassium, sodium, and sulfur; trace minerals include chromium, copper, fluorine, iodine, iron, selenium, and zinc. 5. Starch, a polysaccharide, is a component of foods such as potatoes, breads, rice, and other grains. Lactose, a disaccharide, is found in milk. Sucrose, also a disaccharide, occurs in table sugar, maple syrup, and fruits. Triglycerides are obtained from the diet in fats such as butter, animal fat, milk, and cheese, or form oils such as vegetable oils and fish oils. Cholesterol is also a form of lipid that is a component of all animal-based products such as meats, eggs, and milk. Protein is obtained from meat, dairy products, poultry, fish, beans, and nuts. 6. These individuals must obtain the essential amino acids from a variety of complementary protein sources, which entails eating multiple separate foods, in order to acquire all of the essential amino acids. 7. Since positive nitrogen balance is a significant source of protein, an insufficient protein intake may result in a negative nitrogen balance. 8. RDA is the recommended daily allowance established by the Food and Nutrition Board of the National Academy of Sciences. 9. The USDA MyPlate schematic has five food categories: fruits, grains, vegetables, proteins, and dairy. The largest portion is vegetables. 10. Nutritional labeling may be helpful for those who are interested in eating a healthy diet, those who are meal planning for weightloss programs, and individuals who are on a restricted diet. 11. During the absorptive state, tissues experience an increase in storage of glycogen and triglycerides, and an increase in protein synthesis. 12. During the postabsorptive state, glucagon stimulates glycogenolysis and lipolysis, increasing blood glucose levels. 13. Blood enters the liver lobule through either a branch of the hepatic portal vein or a branch of the hepatic artery. Blood from both vessels merges within sinusoids of the lobule, as it percolates through hepatocytes, on its way to the central vein at the center of the lobule. 14. Cholesterol levels increase with increased levels of cholesterol in the blood. Newly synthesized cholesterol is either utilized for the production of VLDL in the blood, or converted to bile salts. 15. HDLs transport cholesterol from peripheral tissues to the liver. 16. Carbohydrate metabolism: The liver is able to convert noncarbohydrate hydrocarbons into glucose. It can also produce glycogen from glucose by glyconeogenesis, which can be released as needed by glycogenolysis. Protein metabolism: The liver is responsible for the deamination of amino acids, transamination of one amino acid for another, and the synthesis of plasma proteins. Lipid metabolism: Lipid metabolism in the liver includes triglyceride synthesis by lipogenesis, release of fatty acids by lipolysis, conversion of acetyl CoA into ketone bodies, as well as cholesterol and bile salt synthesis. Transport of lipids: The liver produces lipoproteins which transport lipids through the blood. Low-density lipoproteins transport lipids for storage within tissue. High-density lipoproteins transport lipids from tissues to the liver for conversion into bile salts. Other functions: The liver is also responsible for elimination of bilirubin from blood, detoxification of drugs, hormone catabolism, and storage of vitamins A, D, and B12, as well as storage of numerous minerals such as Fe, Zn, Cu, Mg, and Mn.

17. Glycerol is converted to glucose by gluconeogenesis in the liver, and then is catabolized by glycolysis. Beta-oxidation of fatty acids produces acetyl CoA which enters the citric acid cycle. Deaminated amino acids may enter cellular respiration during glycolysis, the intermediate stage, or the citric acid cycle. 18. Excess glucose is converted into acetyl CoA, which is then synthesized into fatty acids, for storage in triglycerides. 19. Metabolic rate increases with exposure to cold temperatures, since increasing BMR can increase body temperature. 20. The core body temperature is the temperature of the vital portions of the body, which consists of the head and torso. The temperature of these regions is kept relatively constant, to prevent damage to vital proteins. 21. The nervous system affects body temperature by regulating sweating, the diameter of peripheral blood vessels, and shivering—all controlled by the hypothalamus. Endocrine control of body temperature involves numerous hormones, many of which adjust various aspects of metabolism such as thyroid hormone, epinephrine, norepinephrine, and testosterone.

Answers to “Do You Know the Basics?” 1. D Feedback: Proteins, minerals, and vitamins are all considered as nutrients. 2. C Feedback: B-complex vitamins and vitamin C are water-soluble. 3. A Feedback: Potatoes contain large amounts of starch, a carbohydrate. 4. C Feedback: Insulin drives the uptake of glucose and amino acids from the blood, following a meal. 5. D Feedback: Insulin causes the uptake and conversion of glucose into either lipid (lipogenesis) or glycogen (glycogenesis). It also induces the uptake of amino acids into cells. 6. D Feedback: Numerous molecules can be catabolized in cellular respiration, including glucose, deaminated amino acids, and fatty acids. 7. B Feedback: Metabolism shifts from the resting to the absorptive state after a meal, interfering with basal metabolic function. 8. D Feedback: The total metabolic rate increases to accommodate the influx of nutrients following a meal. 9. A Feedback: The hypothalamus is involved in the detection and adjustment of body temperature. 10. B Feedback: Thyroid hormone stimulates the activity of Na+/K+ pumps in neurons. This requires energy from ATP, and increases body temperature. 11. Nutrition is the study of the means by which living organisms acquire the nutrients they need to grow and sustain life. 12. Many water-soluble vitamins function as coenzymes. 13. Nonessential amino acids can be made in the body. Essential amino acids must come from the diet. 14. If dietary intake of fat-soluble vitamins exceeds body requirements, the excess is stored within the body fat and may reach toxic levels. 15. Minerals are inorganic ions. Examples of their function in the body include iron binding oxygen to hemoglobin within erythrocytes, calcium forming structural components of bone, and serving as a second messenger in numerous cellular processes,

sodium and potassium establishing resting membrane potentials within cells, and participating in action potentials, iodine forming thyroid hormone, and zinc which is necessary for the binding of transcription factors during protein synthesis. 16. Nitrogen balance refers to the homeostasis between the intakes of nitrogenous compounds such as protein and the excretion of nitrogen containing substances such as urea in urine. A positive nitrogen balance indicates adequate nitrogen intake. A negative nitrogen balance indicates deficient nitrogen intake. 17. During the postabsorptive state, nutrients from the diet are no longer present in the blood, requiring that intracellular nutrient stores be utilized. This is accomplished by glucagon, which stimulates glycogenolysis and lipolysis, increasing blood glucose levels. 18. The liver produces lipoproteins which transport lipids through the blood. Low-density lipoproteins transport lipids for storage within tissue. High-density lipoproteins transport lipids from tissues to the liver for conversion into bile salts. The liver can convert cholesterol into bile salts, eliminating them through the intestines. 19. The liver is able to convert noncarbohydrate hydrocarbons into glucose. It can also produce glycogen from glucose by glyconeogenesis, which can be released as needed by glycogenolysis. The liver is also responsible for the deamination of amino acids, transamination of one amino acid for another, and the synthesis of plasma proteins. Lipid metabolism in the liver includes triglyceride synthesis by lipogenesis, release of fatty acids by lipolysis, conversion of acetyl CoA into ketone bodies, as well as cholesterol and bile salt synthesis. 20. In order to retain heat, the hypothalamus will prevent sweating, by cessation of stimulation of sweat glands. It will stimulate muscle contraction, causing the body to shiver, and it will constrict peripheral blood vessels, thereby preventing the loss of heat to the external environment. At the same time, thyroid hormone will stimulate an increase in Na+/K+ activity in neurons, generating heat as a by-product.

Answers to “Can You Apply What You’ve Learned?” 1. B Feedback: Meat, fish, and poultry contain plentiful essential amino acids. Substitutes such as beans or nuts rarely possess all of the essential amino acids, and must therefore be taken in correct combinations to ensure that all of the essential amino acids are acquired. 2. A Feedback: The hypothalamus is responsible for thermoregulation, which includes initiating sweating and shivering. 3. D Feedback: If dietary intake of fat-soluble vitamins exceeds body requirements, the excess is stored within the body fat and may reach toxic levels. 4. A Feedback: Thyroid hormone is produced by the thyroid gland. It is heavily dependent upon the availability of iodine, and stimulation from the pituitary gland, but it is not associated with liver function. 5. C Feedback: Gluconeogenesis in the liver converts stored molecules, such as fatty acids, into glucose.

Answers to “Can You Synthesize What You’ve Learned?” 1. The MyPlate schematic presents a visual representation of the proportion of food that must come from a particular food category, in order to maintain a healthy diet. 2. Meat, fish, and poultry contain plentiful essential amino acids. In a vegetarian diet, these are not available. Plant substitutes such as beans or nuts rarely possess all of the essential amino acids, and must therefore be taken in correct combinations to ensure that all of the essential amino acids are acquired. 3. Frostbite is damage to superficial cells due to exposure to extreme cold. Damage occurs due to extensive and prolonged vasoconstriction of blood vessels as a result of exposure to extreme cold. This results in oxygen deprivation and tissue death.

Chapter 28 Answers to “What Did You Learn?” 1. Both the male and female reproductive systems consist of gonads which produce gametes, under the control of sex hormones. Both sexes also have accessory reproductive organs. 2. Gonadotropin-releasing hormone is released from the hypothalamus at puberty. It in turn stimulates the release of folliclestimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. 3. The urogenital triangle contains the urethral and vaginal orifices in females and the base of the penis and the scrotum in males. 4. The X and Y chromosomes contain genes that are the primary determinants of sex. 5. Gametes must be haploid, so that when they combine during fertilization, they form a diploid embryo. The embryo can then divide by mitosis, to form a diploid multicellular organism. 6. Mitosis produces two diploid daughter cells that are genetically identical to the parent cell. In contrast, meiosis produces four haploid daughter cells that are genetically different from the parent cell. 7. Chromosomes are duplicated during interface, in preparation for cell division. 8. The term homologous chromosome refers to the duplicate copies of genetic material in a diploid cell—one a maternal copy, the other a paternal copy. After DNA replication, each homologous chromosome consists of two identical sister chromatids, each a copy of the one homolog. 9. Gametes must be haploid, in order to form a diploid organism after fertilization. Gametes are derived from diploid adult stem cells, which must undergo reduction division to produce haploid gametes. 10. Daughter cells become haploid after metaphase I of meiosis. 11. The broad ligament, ovarian ligament, and suspensory ligament are stretches of dense connective tissue that support the uterus and ovary. The ovarian ligament attaches the ovary to the uterine wall. The broad ligament is an extension of the peritoneum that drapes over the uterus, and is attached to the ovary. The suspensory ligament attaches each ovary laterally to the pelvic wall. 12. All of the follicles consist of an oocyte surrounded by granulosa cells. During follicular development, the number of granulosa cells increases, but the oocyte does not change. At the secondary stage of development a fluid-filled antrum forms, which is present through the vesicular phase. 13. At birth, all follicles are primordial follicles. After puberty, under the control of follicle-stimulating hormone, a few of the follicles will start to develop into primary, secondary, and eventually vesicular follicles. 14. FSH triggers the development of primordial follicles. LH triggers ovulation and the formation of the corpus luteum following ovulation. 15. The follicular phase of the ovarian cycle involves the growth and maturation of follicles from the primordial to the vesicular stages. This is associated with increasing levels of estrogen, produced by an increasing number of granulosa cells. Ovulation occurs in response to a surge in LH, resulting from a surge in estrogen levels. The luteal phase is characterized by the presence of the corpus luteum, a remnant of the granulosa cells from the ovulated oocyte. The corpus luteum releases estrogen, progesterone, and inhibin. 16. The infundibulum possesses fimbriae that surround the ovary and bring the ovulated oocyte into the tube. The ampulla is typically the site of fertilization. The isthmus extends from the ampulla to the uterine wall. Lastly, the uterine part of the uterine tube extends medially, through the uterine wall. 17. The perimetrium is contiguous with the broad ligament, which supports the uterus and provides access for blood vessels. The myometrium consists of several layers of smooth muscle, which produce the strong muscular contractions associated with childbirth. The endometrium contains numerous mucous glands, which expand during the uterine cycle. It is the site of implantation. 18. The vagina is an elongated muscular organ that connects the uterus with the outside of the body, and receives the penis during intercourse.

19. The menstrual phase of the uterine cycle is characterized by loss of the stratum functionalis of the endometrium. During the proliferative phase, increasing levels of estrogen from the developing follicle cause proliferation of tubular glands in the stratum functionalis. Proliferation of the stratum functionalis continues during the secretory phase, now under the control of progesterone from the corpus luteum. 20. Fluctuations in levels of estrogen, during the follicular and luteal phases of the ovarian cycle, regulate the proliferation of the stratum functionalis in the uterine cycle. Unlike the relationship between the pituitary gland and the developing follicle, there is no feedback between the uterus and ovary. 21. The labia majora are paired, thickened folds of skin and connective tissue that contain numerous sweat and sebaceous glands. The labia minora are paired folds immediately internal to the labia majora. The vestibule and clitoris are erectile tissues that contain numerous sensory nerve receptors that provide pleasure to the female during sexual intercourse. The prepuce is an external fold of the labia minora that forms a hoodlike covering over the clitoris. The great vestibular gland forms mucus which acts as lubricant for the vagina. 22. The suspensory ligament suspends the lobes of the breast, the individual lobes contain lobules of alveoli that produce milk, and a lactiferous duct drains milk from an individual lobe of the breast. 23. Prolactin is a trophic hormone that stimulates development of alveoli in the breast and milk production. Oxytocin causes the release of milk from mammillary glands. 24. During the excitement phase reproductive organs such as the mammary glands, clitoris, vaginal wall, bulbs of the vestibule, and labia become engorged with blood. During orgasm the woman may experience intense feelings of pleasure. At this point the vagina and uterus contract rhythmically for a period of many seconds. During the resolution phase the uterus returns to its original position and the vaginal wall relaxes. The excess blood leaves the other reproductive organs. 25. The scrotum provides an environment that is cooler than body temperature, which is needed for normal sperm development and maturation. 26. Seminiferous tubules contain sustentacular cells and a population of germ cells. 27. Sustentacular cells produce inhibin, which inhibits FSH from the anterior pituitary gland. Interstitial cells produce testosterone, which inhibits the release of GnRH from the hypothalamus. 28. Spermatogenesis begins when spermatogonia divide by mitosis to form additional spermatogonia and primary spermatocytes. Primary spermatocytes divide during meiosis I to form secondary spermatocytes. Secondary spermatocytes then divide during meiosis II to form spermatids. Final morphologic changes to cellular structure, which allow motility, result in spermatozoa. 29. (1) Spermatogonia produce a new spermatogonium and a primary spermatocyte. (2) Primary spermatocytes complete meiosis I to produce secondary spermatocytes. (3) Secondary spermatocytes complete meiosis II to produce spermatids. (4) Spermatids undergo spermiogenesis, where most of their cytoplasm is shed and a midpiece, tail, and head form. (5) Spermatozoa leave the seminiferous tubules and mature in the epididymis. 30. From the seminiferous tubules male gametes pass through the efferent ductules of the rete testis, through the epididymis, the ductus deferens, the ampulla of the ductus deferens, and then the ejaculatory duct. The ejaculatory duct joins the prostatic urethra in the prostate gland, from there it travels through the membranous urethra, and then the spongy urethra. 31. Seminal vesicles release seminal fluid which contains fructose to nourish spermatozoa, and prostaglandins that dilate the external os of the cervix. The prostate gland produces citric acid which is used as a nutrient for spermatozoa, prostate-specific antigen which helps liquefy semen following ejaculation, and seminalplasmin which is an antibiotic. The bulbourethral gland produces mucus which protects the urethra and serves as a lubricant during sexual intercourse. 32. Seminal fluid from the accessory glands combines with sperm from the testes to make up semen. 33. The corpora cavernosa and corpus spongiosum are erectile tissues within the penis. The corpora cavernosa are paired, whereas the corpus spongeosum is a single structure, which surrounds the spongy urethra. 34. Erection refers to the engorgement of the erectile bodies with blood causing them to become rigid. Ejaculation is the expulsion of semen by rhythmic contractions of smooth muscle in the walls of the urethra.

35. Parasympathetic innervation is necessary to achieve an erection, while sympathetic innervation promotes ejaculation. Relaxation of autonomic activity after sexual excitement returns the penis to a nonaroused state. 36. The sex-determining region gene is responsible for the male phenotype. 37. The paramesonephric ducts persist in the female. The mesonephric ducts persist in the male. 38. The paramesonephric ducts differentiate into the uterine tubes, uterus, and vagina. 39. Sustentacular cells produce anti-Müllerian hormone, which inhibits the development of the paramesonephric ducts. 40. Testosterone causes the differentiation of embryonic tissues into male structures. 41. Good nutrition and health care may cause earlier menarche. 42. Men generally do not stop producing gametes as women do following menopause. Additionally, while men experience a reduction in testosterone levels, this reduction is gradual and not as steep or sudden as the estrogen and progesterone drop seen in menopausal women.

Answers to “Do You Know the Basics?” 1. B Feedback: The penis and labia minora both form from the urogenital folds. 2. B Feedback: High levels of LH cause ovulation. 3. C Feedback: The fornix is a pocket formed by the projection of the cervix into the vagina. 4. C Feedback: An antrum first appears in the secondary follicle. 5. B Feedback: Sustentacular cells produce inhibin. Interstitial cells produce testosterone. 6. B Feedback: The testes produce spermatozoa. They do not produce any other components of semen. 7. C Feedback: Spermatogenesis begins when spermatogonia divide by mitosis to form additional spermatogonia and primary spermatocytes. Primary spermatocytes divide during meiosis I to form secondary spermatocytes. Secondary spermatocytes then divide during meiosis II to form spermatids. Final morphological changes to cellular structure, which allow motility, result in spermatozoa. 8. A Feedback: The epididymis stores sperm until they are fully mature and capable of being motile. 9. D Feedback: Estrogen causes the release of GnRH, which in turn stimulates the release of FSH and LH. 10. A Feedback: The paramesonephric ducts differentiate into the uterine tubes, uterus, and vagina. 11. In contrast to females, male gonads are stored outside of the body cavity, and the system of tubules through which gametes travel is shared, in part, with the urinary system. Gametogenesis in females is no longer initiated after birth. Males continue to produce spermatozoa from spermatagonia into adulthood. There are also numerous similarities between the two systems: The male scrotum is homologous with the labia majora of the female, the labia minora is homologous with the penis, and the clitoris is homologous with the glans penis.

12. GnRH causes the release of FSH and LH from the anterior pituitary gland. FSH stimulates follicular development. LH causes ovulation, and subsequent proliferation of the corpus luteum. Estrogen stimulates the release of GnRH from the hypothalamus and proliferation of tubular glands within the stratum functionalis of the uterine endometrium. Progesterone also stimulates proliferation in the stratum functionalis, but inhibits the release of GnRH from the hypothalamus. 13. Primordial follicles consist of an oocyte surrounded by a single layer of flattened granulosa cells. In a primary follicle the granulosa cells take on a cuboidal appearance. In the secondary follicle stage the follicle contains numerous layers of granulosa cells and a fluid-filled antrum appears for the first time. The vesicular follicle has a large, well-defined antrum, and is ready for ovulation. 14. The perimetrium is contiguous with the broad ligament, which supports the uterus and provides access for blood vessels. The myometrium consists of several layers of smooth muscle which produce the strong muscular contractions associated with childbirth. The endometrium contains numerous mucous glands, which expand during the uterine cycle. It is the site of implantation. 15. The follicular phase of the ovarian cycle is characterized by low levels of both androgens and gonadotropins, and a corresponding loss of the stratum functionalis, resulting in the menstrual phase of the uterine cycle. As follicular development continues during the follicular phase of the ovarian cycle, increasing levels of estrogen stimulate proliferation of the endometrium, which is characteristic of the proliferative phase of the uterine cycle. Ovulation causes a drop in estrogen levels, but does not affect the proliferative phase of the uterus. Similarly, during the luteal phase of the ovarian cycle, progesterone is produced by the corpus luteum, which maintains proliferation in the uterus. 16. GnRH from the hypothalamus stimulates the release of FSH and LH from the anterior pituitary gland. LH stimulates interstitial cells to produce testosterone, and FSH stimulates sustentacular cells to produce androgen-binding protein. Testosterone stimulates spermatogenesis and also inhibits GnRH in the hypothalamus. In response to high sperm levels, sustentacular cells release inhibin which causes inhibition of FSH. 17. Sustentacular cells produce androgen-binding protein, which keeps testosterone levels high in the testis. 18. (1) Diploid spermatogonia produce a new spermatogonium and a primary spermatocyte. (2) Primary spermatocytes (diploid) complete meiosis I to produce haploid secondary spermatocytes. (3) Secondary spermatocytes complete meiosis II to produce haploid spermatids. (4) Spermatids undergo spermiogenesis, where most of their cytoplasm is shed in a midpiece, tail, and head form. (5) Haploid spermatozoa leave the seminiferous tubules and mature in the epididymis. 19. During an erection, blood flows into venous spaces within the corpora cavernosa of the penis in response to nitric oxide, which is released in response to parasympathetic stimulation. Simultaneously, the expanding erectile tissue compresses the veins that drain the penis, and prevent blood from leaving the tissue. Ejaculation occurs due to rhythmic contraction of smooth muscle in the walls of the urethra, under sympathetic stimulation from the nervous system. 20. The mesonephric ducts form the efferent ductules, epididymis, ductus deferens, and the seminal vesicle. The paramesonephric ducts form the uterine tube, uterus, and vagina.

Answers to “Can You Apply What You’ve Learned?” 1. C Feedback: Spermatozoa are extremely sensitive to increases in temperature. 2. C Feedback: Ovulation occurs midway through the ovarian cycle. The optimum time for fertilization would then be after ovulation. 3. A Feedback: LH stimulates interstitial cells to produce testosterone, and testosterone stimulates spermatogenesis. 4. B Feedback: Sexually transmitted infections are a leading cause of pelvic inflammatory disease in women, in which the reproductive organs become infected. 5. B Feedback: Follicle-stimulating hormone causes the development of primordial follicles.

Answers to “Can You Synthesize What You’ve Learned?” 1. Down syndrome usually results from a trisomy of chromosome 21. The disorder is characterized by intellectual disability, slanting epicanthal folds, heart defects, poor muscle tone, and short stature. The incidence of Down syndrome increases with the mother’s age, suggesting that nondisjunction problems may occur due to a maternal age effect. 2. Two weeks following the previous menstruation is the optimum time for fertilization. This is the time at which estrogen levels peak, causing spike in the release of LH, and subsequent ovulation. Birth control pills contain progestins to inhibit the release of LH, thereby preventing ovulation. 3. Male and female external genitalia do not usually develop until week 20 of development.

Chapter 29 Answers to “What Did You Learn?” 1. The pre-embryonic period ends with implantation, which is the start of the embryonic period. 2. A lack of motility, or leaking out from the vagina, prevents many sperm from reaching the secondary oocyte. Many more get lost in the uterus, due to churning of the uterine walls. Only a few hundred of the millions that are ejaculated reach the oocyte. 3. Fertilization involves (1) sperm penetrating the corona radiate, (2) sperm undergoing acrosome reaction and penetrating the zona pellucida, and finally (3) the sperm and oocyte plasma membranes fuse. 4. The morula begins with 16 cells. 5. The blastocyst consists of an outer trophoblast, and a mass of pluripotent stem cells called an embryoblast. 6. The syncytiotrophoblast releases hCG, which mimics LH, and without which menstruation would occur. 7. hCG is continuously released only if implantation has occurred. The presence of hCG in blood or urine would therefore indicate pregnancy. 8. The bilaminar germinal disc consists of a hypoblast and an epiblast layer. 9. The yolk sac develops from the hypoblast, the amnion develops from the epiblast, and the chorion develops from the syncytiotrophoblast and the cytotrophoblast. 10. The placenta is responsible for (1) the exchange of nutrients, waste products, and respiratory gases between the maternal and fetal blood, (2) transmission of maternal antibodies to the developing embryo or fetus, and (3) production of estrogen and progesterone to maintain and build the uterine lining 11. The primary germ layers are formed during gastrulation. The process begins with the formation of a primitive streak, followed by invagination. The hypoblast develops into the endoderm, the epiblast develops into the ectoderm, and a new mesoderm layer forms between the two. 12. Cephalocaudal folding of the embryonic disc causes the head and tail to fold on themselves longitudinally along the embryo. Transverse folding forms the edges of the embryo laterally to form the cylinder that will become the trunk. 13. The ectoderm gives rise to the epidermis of skin, nervous tissue and sense organs, pituitary gland, adrenal medulla, enamel of teeth, and the lens of the eye. The mesoderm gives rise to the dermis of skin, epithelial lining of blood vessels, lymph vessels and serous membranes, muscle tissue, connective tissue, adrenal cortex, heart, kidneys, ureters, internal reproductive organs, and spleen. The endoderm gives rise to epithelial lining of respiratory tract, GI tract, urinary tract, reproductive tract, tympanic cavity and auditory tube, as well as most of the liver, gallbladder, pancreas, tonsils, thyroid gland, parathyroid glands, and thymus. 14. Differentiation during the embryonic period is highly susceptible to the effects of teratogens. 15. The fetal period is characterized by maturation of tissues and organs, and rapid growth of the body. 16. The first trimester is characterized by differentiation of the embryo whereas the second trimester is marked by growth of the embryonic and maternal tissues. During the third trimester the fetus grows even faster, and the mother’s body prepares for labor and delivery. 17. Estrogen and progesterone suppress the ovarian cycle by inhibiting LH and FSH. They also facilitate uterine development, mammary gland enlargement, and fetal growth. 18. CRH causes the release of aldosterone, which in turn causes the retention of fluids, and an increase in blood volume. It also plays a role in the regulation of the length of pregnancy. HPL affects maternal nutrition, specifically fatty acid and glucose metabolism. It also inhibits the effects of insulin. Oxytocin induces milk ejection, and prolactin stimulates milk production in the breast. 19. The enlarged uterus pushes against the diaphragm, compresses many of the abdominopelvic organs, and impinges on the bladder.

20. Areolae darken in response to melanocyte-stimulating hormone, and mammillary glandular tissue expands in response to prolactin. 21. Increased levels of corticosteroids, estrogen, progesterone, and human placental lactogen result in increased insulin sensitivity. 22. The fetus, placenta, breast and uterine enlargement, and fluid retention account for weight gain during pregnancy. 23. During the first trimester the heart rate and stroke volume increase in order to produce cardiac output sufficient to circulate the 50% increase in blood volume of both the mother and conceptus. This causes a significant increase in blood pressure. 24. Increased sensitivity of chemoreceptors to blood CO2 levels increases the rate of ventilation and decreases the concentration of CO2 in the blood. Lower blood CO2 levels facilitate the diffusion of gases across the placenta. Increased ventilation and tidal volume cause an increase in consumption of oxygen to meet the oxygen demands of both mother and fetus. 25. Compression of the ureter or kidneys by the uterus can cause drainage issues, which can cause urinary tract infections. 26. Estrogen counteracts progesterone, which has a calming effect on the myometrium. As estrogen levels increase they cause an increase in the number of oxytocin receptors in the myometrium, making it more sensitive to the hormone. 27. Braxton-Hicks contractions have the following characteristics: (1) They tend to be irregularly spaced and do not become more frequent as time passes. (2) They tend to be relatively weak, do not increase in intensity, and may stop entirely if the woman changes position or activity. (3) The pain from these contractions is usually limited to the lower abdomen and pelvic region. (4) The pain from the contractions may stop or change in response to movement. (5) They do not lead to the cervical changes seen in the three stages of labor. 28. True labor contractions have the following characteristics: (1) They tend to increase in frequency over time. (2) Contractions increase in intensity as labor progresses. (3) The pain from the contractions tends to radiate from the upper abdomen inferiorly to the lower back (or vice versa). (4) The pain from the contractions does not go away or change in response to movement. (5) The contractions facilitate cervical dilation and expulsion of the fetus and placenta. 29. Uterine contractions result in the fetus’s head pushing against the cervix. This manual stretching of the cervix and uterine contractions both signal the hypothalamus to secrete more oxytocin, which stimulates stronger contractions. In addition, uterine contractions stimulate the placenta to secrete prostaglandins, which also result in stronger uterine contractions. 30. The dilation stage begins with the onset of regular uterine contractions and ends when the cervix is effaced and dilated to 10 centimeters in diameter. The expulsion stage begins with the complete dilation of the cervix and ends with the expulsion of the fetus from the mother’s body. The placental stage occurs after the baby is expelled. 31. During the placental stage, uterine contractions prevent bleeding by compressing uterine blood vessels, and expel remaining embryonic tissues. Fragments of placenta left in the uterus can lead to extensive bleeding or other postpartum complications. 32. Once the first breath is taken, the lungs become inflated and surfactant in the alveoli keeps the alveoli open. 33. When the neonate takes its first breath, pulmonary resistance drops, and the pulmonary arteries dilate. 34. Because of the postpartum drop in estrogen and progesterone levels, cyclical hair loss returns, chemoreceptors become less sensitive thus lowering the respiratory rate and increasing blood carbon dioxide saturation, and CRH levels decline, possibly contributing to postpartum depression. 35. Fluids are lost postpartum through the expulsion of amniotic fluid, excessive urination, excessive bleeding and lochia, and excessive sweating. 36. Infant suckling stimulates mechanoreceptors in nipples to send sensory impulses to the hypothalamus. The hypothalamus releases oxytocin through the posterior pituitary. Oxytocin then triggers the release of milk from acini in the breast. Simultaneously, stimulation of the breast causes a decrease in the production of dopamine in the hypothalamus, which triggers the release of prolactin from the anterior pituitary gland, which in turn stimulates milk production. 37. Oxytocin facilitates shrinkage of the uterus postpartum by stimulating uterine contractions. Since breastfeeding stimulates oxytocin release, it also causes uterine contractions.

38. All of the offspring would have the dominant phenotype; however, there is a 50% chance that they are homozygous dominant for the trait, and a 50% chance that they are heterozygous. 39. Codominant alleles are both expressed in the phenotype, without mixing into an intermediate phenotype, which occurs in incomplete dominance. 40. All of her male children would be homozygous for the trait, and would therefore be color-blind. All of her female children would be heterozygous for the trait, and have normal vision. 41. Nutrition has a significant effect upon growth and development. Poor nutrition greatly decreases brain development and growth.

Answers to “Do You Know the Basics?” 1. D Feedback: The trophoblast forms all of the extra embryonic tissues that interface with the maternal environment. 2. B Feedback: Compaction of cells occurs in the embryo, prior to implantation. 3. C Feedback: Migration of cells from the epiblast forms the mesoderm of the germinal disc. 4. A Feedback: During gastrulation, the epiblast and hypoblast are formed from the embryoblast. 5. B Feedback: The mesoderm, along with the endoderm and ectoderm, are part of the embryo. 6. B Feedback: Although blood pressure increases during the first trimester, in order to accommodate a higher blood volume, it is stabilized during the second trimester due to vasodilation caused by a decreased sensitivity to angiotensin. 7. A Feedback: Within a few days after giving birth, estrogen and progesterone levels drop, because the uterine lining no longer needs to be maintained for pregnancy. 8. D Feedback: Since neither parent has freckles, they are both homozygous recessive for the trait. Therefore, they cannot have children with the dominant allele. 9. D Feedback: Most human traits exhibit polygenic inheritance. 10. C Feedback: 50% of her gametes will carry the recessive allele. 11. Fertilization involves (1) sperm penetrating the corona radiate, (2) sperm undergoing acrosome reaction and penetrating the zona pellucida, and finally (3) the sperm and oocyte plasma membranes fuse. 12. The notochord develops into a neural tube and provides the axis of the body. The paraxial mesoderm gives rise to the axial skeleton, most muscle, most of the cartilage, dermis, and connective tissues. The intermediate mesoderm forms most of the kidneys, ureters, and the reproductive system. The lateral plate mesoderm gives rise to the spleen, adrenal cortex, most of the components of the cardiovascular system, the serous membranes of the body cavities, and all the connective tissue components of the limbs. The head mesenchyme forms connective tissues and musculature of the face. 13. The first trimester is characterized by differentiation of the embryo whereas the second trimester is marked by growth of the embryonic and maternal tissues. Differentiation during the embryonic period is highly susceptible to the effects of teratogens, because slight changes can affect significant damage to the developing embryo.

14. The embryonic period is characterized by major differentiation events such as gastrulation, and the formation of the body form. The fetal period is characterized by maturation of these established tissues and organs, and rapid growth of the body. 15. Estrogen and progesterone suppress the ovarian cycle by inhibiting LH and FSH. They also facilitate uterine development, mammary gland enlargement, and fetal growth. CRH produced by the placenta causes the release of aldosterone, which in turn causes the retention of fluids, and an increase in blood volume. It also plays a role in the regulation of the length of pregnancy. HPL affects maternal nutrition, specifically fatty acid and glucose metabolism. It also inhibits the effects of insulin. Postpartum, oxytocin induces milk ejection, and prolactin stimulates milk production in the breast. 16. The dilation stage begins with the onset of regular uterine contractions and ends when the cervix is effaced and dilated to 10 centimeters in diameter. The expulsion stage begins with the complete dilation of the cervix and ends with the expulsion of the fetus from the mother’s body. The placental stage occurs after the baby is expelled. During the placental stage, uterine contractions prevent bleeding by compressing uterine blood vessels, and expel remaining embryonic tissues. 17. Infant suckling stimulates mechanoreceptors in nipples to send sensory impulses to the hypothalamus. The hypothalamus releases oxytocin through the posterior pituitary. Oxytocin then triggers the release of milk from acini in the breast. Simultaneously, stimulation of the breast causes a decrease in the production of dopamine in the hypothalamus, which triggers the release of prolactin from the anterior pituitary gland, which in turn stimulates milk production. 18. Fluids are lost postpartum through the expulsion of amniotic fluid, excessive urination, excessive bleeding and lochia, and excessive sweating. 19. In strict dominant-recessive inheritance, expression of the recessive allele is always masked by expression of the dominant allele. Polygenic inheritance involves the interaction of multiple genes. In codominance, both genotypes are expressed in the phenotype. In incomplete dominance, an intermediate phenotype is seen for the heterozygous genotype. 20. In order for a female to express a recessive X-linked trait, she must be homozygous for the recessive allele. A heterozygous female will be a carrier, and will not express the recessive phenotype. Males, however, can only carry one copy of the gene; therefore, they cannot have a dominant allele to mask the expression of the recessive allele. They cannot be heterozygous. An X-linked dominant will be expressed in either males or females. Males cannot be heterozygous for the trait. Females may be either homozygous dominant or heterozygous for an X-linked dominant trait.

Answers to “Can You Apply What You’ve Learned?” 1. D Feedback: Blood pressure and heart rate are usually slightly elevated during pregnancy to accommodate the increased blood volume. Increased insulin resistance results in glucose remaining longer in the blood, to provide availability to the fetus. Urine content will also vary due to the presence of waste from the fetus as well as maternal waste. Finally, weight gain of up to 20 pounds is not uncommon during pregnancy. 2. A Feedback: The crown-rump length of a fetus at 20 weeks should be approximately 19 centimeters. 3. B Feedback: Uterine contractions result in the fetus’s head pushing against the cervix. This manual stretching of the cervix and uterine contractions both signal the hypothalamus to secrete more oxytocin, which stimulates stronger contractions. 4. A Feedback: Oxytocin stimulates the release of milk from breast acini and causes uterine contractions. Infant suckling stimulates mechanoreceptors in nipples to send sensory impulses to the hypothalamus. The hypothalamus releases oxytocin through the posterior pituitary, which then has its effect in both the breast tissue and the myometrium of the uterus. 5. C Feedback: Males receive an X chromosome from their mother and a Y chromosome from their father. Therefore, a male with an Xlinked trait inherited it from his mother. Since it is a recessive trait, a heterozygous mother is a carrier for the allele. She does express the recessive phenotype because it is masked by the dominant allele.

Answers to “Can You Synthesize What You’ve Learned?” 1. Since most differentiation and organogenesis occurs during the embryonic stage of development, that is the point at which the conceptus is most susceptible to teratogenesis.

2. Alcohol is a powerful teratogen. Since most differentiation occurs during the first trimester of development, exposure to alcohol can be damaging to the embryo. 3. If their father was homozygous for the autosomal dominant disorder, they will both have inherited one dominant allele, and will therefore have a 100% chance of getting the disorder. If the father was heterozygous, then they each would have a 50% chance of acquiring the dominant allele and subsequently getting the disorder. Since they each have a 50% chance of acquiring the allele, there is a 25% probability that they will both get the disorder.