Human Anatomy Medical School Crash Course™
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Contents Introduction ......................................................................................................................................... 6 Chapter 1: Introduction to Anatomy .................................................................................................. 1 Anatomical position and directional landmarks ........................................................................... 1 Body planes and sections.................................................................................................................. 3 Body cavities ..................................................................................................................................... 4 Key takeaways .................................................................................................................................. 5 Review questions .............................................................................................................................. 6 Chapter 2: Organization of the Human Body.................................................................................... 9 Anatomy of a generalized cell ........................................................................................................... 9 Epithelial tissue ............................................................................................................................... 12 Connective tissue ............................................................................................................................ 15 Muscle tissue................................................................................................................................... 18 Nervous tissue................................................................................................................................. 19 Key takeaways ................................................................................................................................ 19 Review questions ............................................................................................................................ 20 Chapter 3: Skin and Body Membranes............................................................................................ 23 Classification of body membranes ................................................................................................... 23 Integumentary System..................................................................................................................... 24 Key takeaways ................................................................................................................................ 27 Review questions ............................................................................................................................ 28 Chapter 4:Skeletal System ............................................................................................................... 31 Bone: Overview ............................................................................................................................... 31 Axial Skeleton.................................................................................................................................. 35 Appendicular Skeleton..................................................................................................................... 42 Joints ............................................................................................................................................... 47 Synovial joints ................................................................................................................................. 48 Key takeaways ................................................................................................................................ 48 Review Questions ........................................................................................................................... 49 Chapter 5: Muscular System ............................................................................................................ 52 Overview of Muscles ....................................................................................................................... 52 Skeletal muscle activity ................................................................................................................... 53 Muscle movements, types, and names ........................................................................................... 54 Types of muscles ............................................................................................................................ 55 Muscles in the human body ............................................................................................................. 57 Key takeaways ................................................................................................................................ 63 Review Questions ........................................................................................................................... 64 Chapter 6: Nervous System ............................................................................................................. 67 Organization of the nervous system ................................................................................................ 67
Nervous tissue – Structure and function .......................................................................................... 68 Central nervous system ................................................................................................................... 70 Peripheral nervous system .............................................................................................................. 73 Key takeaways ................................................................................................................................ 76 Review Questions ........................................................................................................................... 77 Chapter 7: Special senses................................................................................................................ 80 The eye ........................................................................................................................................... 80 The ear ............................................................................................................................................ 83 Chemical senses: taste and smell ................................................................................................... 85 Key takeaways ................................................................................................................................ 86 Review Questions ........................................................................................................................... 86 Chapter 8: Endocrine system .......................................................................................................... 89 The endocrine organs...................................................................................................................... 89 Hormones of the Ovaries................................................................................................................. 96 Hormones of the testes ................................................................................................................... 96 Placenta .......................................................................................................................................... 97 Key takeaways ................................................................................................................................ 97 Review Questions ........................................................................................................................... 98 Chapter 9: Blood and the Circulatory system .............................................................................. 101 Composition and functions of blood .............................................................................................. 101 Blood groups and transfusions ...................................................................................................... 104 Anatomy of the heart ..................................................................................................................... 105 Anatomy of blood vessels.............................................................................................................. 108 Lymphatic system .......................................................................................................................... 109 Key takeaways .............................................................................................................................. 110 Review Questions ......................................................................................................................... 110 Chapter 10: Respiratory System .................................................................................................... 113 Anatomy of the respiratory system ................................................................................................ 113 Key takeaways .............................................................................................................................. 117 Review Questions ......................................................................................................................... 118 Chapter 11: Digestive system ........................................................................................................ 121 Anatomy of the digestive system ................................................................................................... 121 Functions of the digestive system ................................................................................................. 124 Key takeaways .............................................................................................................................. 126 Review Questions ......................................................................................................................... 127 Chapter 12: Urinary system ........................................................................................................... 130 Kidneys.......................................................................................................................................... 130 Ureter, bladder, and urethra .......................................................................................................... 132 Key takeaways .............................................................................................................................. 133
Review Questions ......................................................................................................................... 134 Chapter 13: Reproductive system ................................................................................................. 137 The male reproductive system ...................................................................................................... 137 The female reproductive system ................................................................................................... 140 Key takeaways .............................................................................................................................. 142 Review Questions ......................................................................................................................... 142 Test Questions ................................................................................................................................ 145 Conclusion: ..................................................................................................................................... 162
Introduction Anatomy is the study of the structure and shape of the body and body parts and their relationships to one another. Whenever we look at our own body or study large body structures such as the heart or bones, we are observing gross anatomy. This means we are studying large, easily observable structures. On the other hand, if a microscope is used to see very small structures in the body, we are studying microscopic anatomy. The cells and tissues of the body can only be seen through a microscope. This audio book will seek to develop a deeper understanding of both the gross and microscopic structured within the human body. Each chapter will aim to take the student through the fundamentals of the different organ systems, and develop the students’ knowledge from these simple fundamentals through to a well-rounded, indepth understanding of the structure and function of the various structures, organs, tissues and organ systems within the body.
Chapter 1: Introduction to Anatomy In this chapter, we will introduce the various concepts associated with the study of human anatomy. We will investigate the anatomical positions and directional landmarks that are used to orientate the observer to the precise positions of organs or structures and will divide the body up into separate sections or cavities based upon the standardized body planes.
Anatomical position and directional landmarks Anatomical position To accurately describe body parts and position, an initial reference point must be used. The anatomical position refers to the individual standing up straight, facing forward, with the hands at their sides. Most importantly, the palms of the hands must be turned to face forward, rather than the usual position of facing the thighs. The regional terms introduced in the next section are all based on this standardized body position. Regional terms Regional and directional terms are used by medical professionals to explain exactly where one body structure is in relation to another. This provides a clear understanding of where a particular structure is to be found. The following list of directional terms are all standard in the study of anatomy, and are used in reference to the anatomical position: o Superior refers to landmarks found towards the upper part of a structure or the body. For example, the forehead is superior to the nose. o Inferior refers to landmarks found towards the lower part of a structure or the body. For example, the nose is inferior to the forehead. o Anterior refers to landmarks found towards the front of a structure or the body. For example, the breastbone is anterior to the spine. o Posterior refers to landmarks found toward the back of a structure or the body. For example, the spine is posterior to the breastbone. o Medial refers to landmarks found towards the midline of a structure or the body. For example, the heart is medial to the arm.
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o Lateral refers to structures found towards the outside, or away from the midline of a structure or the body. The arm is lateral to the heart. o Proximal refers to a landmark found closer to the origin of a body part or the point of attachment of a limb to the body trunk. For example, the elbow is proximal to the wrist, meaning it is closer to the shoulder joint than the wrist is. o Distal refers to a landmark found further from the origin of a body part or the point of attachment of a limb to the body trunk. For example, the wrist is distal to the elbow, meaning it is further away from the shoulder joint than the elbow is. o Superficial refers to structures found towards the body surface. For example, the skin is superficial to the skeleton. o Deep refers to structures found away from the body surface, or more internal. For example, the skeleton is deep to the skin. Anterior body landmarks Anterior body landmarks are visible landmarks on the anterior surface of the body. They combine with the directional terms to give a more accurate indication of where a structure is to be found. The anterior body landmarks are as follows: • • • • • • • • • • • • • • •
Abdominal, meaning the anterior body trunk inferior to the ribs. Antecubital, meaning the anterior surface of the elbow. Axillary, meaning the armpit. Brachial, meaning the arm. Buccal, meaning the cheek area. Cervical, meaning the neck region. Digital, meaning the fingers and toes. Femoral, meaning the thigh. Inguinal, meaning where the thigh meets the body trunk. Oral, meaning with the mouth. Orbital, meaning the eye area. Patellar, meaning the anterior part of the knee. Pubic, meaning the genital region. Thoracic, meaning the chest. Umbilical, meaning the navel region. 2
Posterior body landmarks. Posterior body landmarks are visible landmarks on the posterior surface of the body. They combine with the directional terms to give a more accurate indication of where a structure is to be found. The posterior body landmarks are as follows: • • • • • • •
Deltoid, referring to the curve of the shoulder formed by the deltoid muscle. Gluteal, referring to the buttocks. Lumbar, referring to the area of the back between the ribs and the hips. Occipital, referring to the posterior surface of the head. Popliteal, referring to the posterior part of the knee. Scapular, referring to the shoulder blade region. Sural, referring to the posterior surface of the lower leg, or the calf.
Body planes and sections. When preparing to look at the internal structures of the body, medical students find it necessary to make a section or cut. These sections are made along an imaginary line called a plane. Since the body is three-dimensional, we can refer to three types of planes or sections that lie at right angles to each other. Figure 1 shows the different body planes:
Figure 1 3
Sagittal section The sagittal section is a cut made along the lengthwise, or longitudinal, plane of the body, dividing the body into left and right parts. When made along the midline it can be referred to as midsagittal. A midsagittal section divides the left and right parts evenly. Frontal section A frontal section is a cut made along a lengthwise plane that divides the body or structure into anterior and posterior parts. It is also referred to as a coronal section. Transverse section A transverse section is a cut made along a horizontal plane, which divides the body into superior and inferior parts. It is also referred to as a cross-section.
Body cavities The body has two sets of internal cavities that offer different degrees of protection to the organs and structures within them. Figure 2 shows the two major body cavities:
Figure 2 4
Dorsal body cavity The dorsal body cavity is located in the posterior aspect of the body. It has two subdivisions known as the cranial cavity and the spinal cavity. The cranial cavity is the space inside the skull. The brain is well protected as it is found within the cranial cavity. The spinal cavity extends from the cranial cavity, nearly to the end of the vertebral column. The spinal cord is protected by the vertebrae which enclose the spinal cavity. Ventral body cavity The ventral body cavity is located in the anterior aspect of the body. It is much larger than the dorsal cavity and contains all the structures within the chest and abdomen. The ventral body cavity is divided into the thoracic cavity and the abdominopelvic cavity. The thoracic cavity is separated from the abdominopelvic cavity by the diaphragm. The thoracic cavity is superior to the abdominopelvic cavity and houses the vital organs such as the heart and lungs. These are protected by the rib cage. The abdominopelvic cavity is inferior to the thoracic cavity, and can be further subdivided into the abdominal cavity and the pelvic cavity. The abdominal cavity houses the stomach, liver, intestines and other digestive organs. The pelvic cavity houses the reproductive organs, bladder and rectum. There is no physical structure separating the abdominal cavity from the pelvic cavity.
Key takeaways • • • • •
Anatomy is the study of structure. Anatomical terminology is relative and assumes that the body is in the anatomical position. Directional terms and landmarks are used to identify the specific locations of structures. The body and its structures may be subdivided into three sections known as the sagittal, frontal and transverse sections. The dorsal and ventral cavities are body cavities that offer protection to the organs and structures within them.
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Review questions Question 1 Which of the following describes the anatomical position? A. Upright, facing forward, hands at the sides, palms facing forward. B. Upright, facing forward, hands outstretched, palms facing forward. C. Upright, facing forward, hands outstretched, palms facing downward. D. Upright, facing forward, hands at the sides, palms facing the thighs. The answer is A. Upright, facing forward, hands at the sides, palms facing forward. Question 2 Which of the following is not a common directional term? A. B. C. D.
Superior Inferior Distal Axillary
The answer is D, Axillary. Question 3 If one were to say that the elbow is proximal to the wrist, it would mean… A. B. C. D.
The elbow is closer to the wrist than the shoulder. The elbow is closer to the shoulder than the wrist. The wrist and elbow are in close proximity. The elbow articulates with the wrist.
The answer is B, the elbow is closer to the shoulder than the wrist.
Question 4 A medical journal refers to inflammation of the cheek area. Which body landmark would they likely have used? A. B. C. D.
Inguinal Buccal Brachial Orbital
The answer is B, Buccal.
Question 5 A patient complains of pain in the lumbar region. The area you will examine is… 6
A. B. C. D.
Part of the back superior to the scapula. Part of the back between the lowest ribs and the hips. The broad surface of the back between the scapulae. None of the above.
The answer is B, the part of the back between the lowest ribs and the hips. Question 6 During a cadaver study, you are asked to make a coronal section. This would divide the cadaver into… A. B. C. D.
Superior and Inferior parts. Proximal and distal parts. Anterior and posterior parts. Medial and lateral parts.
The answer is C, medial and lateral parts. Question 7 The cranial and spinal cavities form part of which greater body cavity… A. B. C. D.
Ventral body cavity Thoracic body cavity Pelvic body cavity Dorsal body cavity
The answer is D, dorsal body cavity. Question 8 The section that divides the body into the superior and inferior parts is known as the… A. B. C. D.
Sagittal section Transverse section Frontal section Ventral section
The answer is B, the transverse section. Question 9 The abdominopelvic cavity houses which organs? A. B. C. D.
Stomach Bladder Intestines All of the above
The answer is D, all of the above, being the stomach, bladder and intestines. Question 10 7
Which structure separates the thoracic cavity from the abdominopelvic cavity? A. B. C. D.
Diaphragm Pelvis Pubic Symphysis None of the above.
The answer is A, the diaphragm.
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Chapter 2: Organization of the Human Body In this chapter, we will develop a working knowledge of the functions of the cells and tissues that make up the human body.
Anatomy of a generalized cell The human body is made of trillions of different cells, each providing an essential function. Groups of cells with a common function form tissues. No one cell type is exactly like the others, but they do possess many common structural and functional features. This section will discuss the generalized cell, which demonstrates the many typical structures and functions common to all cells. The nucleus The control center of a cell is the nucleus. The nucleus contains all the genetic material of the cell, called deoxyribonucleic acid or DNA. DNA contains the blueprint of instructions for all the functions of the body, is responsible for the building of proteins and is necessary for cell reproduction. The human cell does not have a defined shape and can be defined as having an irregular shape. The nucleus of the cell, while usually oval or spherical, can conform to the shape of the cell. The nucleus has three distinct regions. These are the nuclear membrane, nucleoli, and chromatin. The nuclear membrane is a double membrane that surrounds the nucleus. The two layers of the membrane fuse at several points and nuclear pores penetrate both membranes at these junctions. The nuclear membrane is a selectively permeable membrane, but passage of substances is easier due to the relatively large nuclear pores. The nuclear membrane encloses a jelly-like fluid called nucleoplasm, in which the nucleoli and chromatin are suspended. The nucleoli are small, dark, round bodies with the nucleus. Ribosomes, which are the sites for protein synthesis, assemble around the nucleoli. When the cell is not dividing, the DNA is combined with protein and forms a loose network of threads called chromatin. These chromatin threads coil and condense to form chromosomes during cell mitosis. When the cell divides to form two daughter cells, the chromosomes are evenly split between the two cells, thus ensuring that the genetic material of the cell is reproduced in each daughter cell. 9
Figure 3 is an illustration of the different parts of the human cell:
Figure 3 The plasma membrane The flexible plasma membrane is a flexible, transparent barrier that contains the cell contents and separates them from the surrounding environment. The plasma membrane is responsible for defining the outer limits of the cell and plays a dynamic role in cell communication. Gap junctions within the plasma membrane allow chemical molecules such as nutrients and ions to pass directly from cell to cell. The cytoplasm The cytoplasm consists of cellular material outside of the nucleus but within the plasma membrane. It is the site of most cellular activities and consists of the cytosol, organelles, and inclusions. The cytosol is a semi-transparent fluid in which the other elements are suspended. The cytosol is primarily water, with nutrients and a variety of other solutes dissolved into it.
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The organelles are the metabolic components of the cell, and are each responsible for a specific function within the cell. These functions are discussed in the next section. The inclusions are not functional units, but are chemical substances that vary dependent on the cell type. Most inclusions are stored nutrients or cell products such as fat molecules, glycogen granules, and pigments. Cytoplasmic organelles The cytoplasmic organelles are specialized cellular components. Each organelle is responsible for a specific function to maintain the life of the cell. Each organelle is surrounded by a membrane boundary which allows it to maintain a stable internal environment different from that of the surrounding cytosol. The organelles and their functions are as follows: Ribosomes are dark, round bodies made predominantly of proteins. Ribosomes are the sites of protein synthesis and either float freely in the cytoplasm or attach to membranes. Those attached to membranes form a network called the rough endoplasmic reticulum. The endoplasmic reticulum is a system of fluid-filled canals that twist throughout the cytoplasm. It accounts for approximately half of the cells membranes, and provides a network of channels for the transport of substances such as proteins from one cell to another. The rough endoplasmic reticulum is studded with ribosomes. The ribosomes manufacture proteins are transported by the endoplasmic reticulum. A further function of the rough endoplasmic reticulum is the manufacture of membrane lipids, which essentially provide the building blocks for all cell membranes. The smooth endoplasmic reticulum is a continuation of the rough endoplasmic reticulum, but plays no role in protein synthesis. It is primarily responsible for cholesterol synthesis and fat metabolism. The Golgi apparatus appear as a stack of flattened membranous sacs. It is usually found close to the nucleus and has the primary function of modifying and packaging proteins. Lysosomes are membrane sacs containing powerful digestive enzymes. The enzymes are capable of digesting worn out or nonusable cell structures and foreign substances that enter the cell. Lysosomes are particularly abundant in white blood cells. 11
Peroxisomes are membranous sacs that contain powerful oxidase enzymes. These enzymes use oxygen to detoxify harmful or poisonous substances. Mitochondria a threadlike organelles which can continuously change shape. Mitochondria are the site of cellular respiration, in which oxygen is used to break down foods and produce energy. Because mitochondria provide energy, they are referred to as the powerhouse of the cell. The centrioles are paired organelles that lie close to the nucleus. They are rod-shaped bodies that lie at right angles to each other. The centrioles play a key role in the division of nuclear elements during cell division.
Epithelial tissue Epithelial tissue, or epithelium, is the lining, covering and glandular tissue of the body. Glandular epithelium forms various glands in the body. Covering and lining epithelium covers all free body surfaces and contains versatile cells. These tissues form both the outer layer of the skin as well as the lining of body cavities. Figure 4 describes the different types of epithelium:
Figure 4 Since epithelial tissue forms the boundaries between our bodies and the outside world, all substances given off or received by the body must pass through the epithelium. Its functions, therefore, include protection, absorption, filtration, and secretion.
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Special characteristics of epithelium Epithelial cells fit closely together to form continuous sheets of cells. These cells are bound together at several points by cell junctions. The membranes always have one unattached surface called the apical surface. This surface is exposed to the exterior of the body or to the cavity of an internal organ. Exposed surfaces are modified to suit their environment, and are either smooth or may exhibit microvilli or cilia. The lower surface of epithelium lies on a basement membrane. Epithelial tissues are avascular, meaning they have no bloody supply of their own. They rely on diffusion of oxygen and nutrients from the capillaries of the underlying connective tissue. Epithelial cells are able to regenerate quickly and easily when in a healthy, well-nourished state. Epithelia are classified according to shape and arrangement. Squamous cells are flattened like fish scales, cuboidal cells are cube shaped, and columnar cells are shaped like columns. There are two classifications of epithelia by arrangement. Simple epithelia refers to one layer of cells, while stratified epithelium refers to more than one layer of cells. The terms describing shape and arrangement are combined to describe the epithelium fully. These categories are discussed in the next section. Simple epithelia Simple epithelial tissues are very thin, and are thus most useful for absorption, secretion, and filtration. Simple squamous epithelium is a single layer of squamous cells lying on a basement membrane. This type of epithelium is usually found where filtration or exchanges of substances by rapid diffusion takes place. Simple squamous epithelium is found in the alveoli of the lungs, where gaseous exchange takes place, and along the capillary walls, where nutrients and gases are exchanged with body tissues. Simple cuboidal epithelium is a single layer of cuboidal cells on a basement membrane. These cells are common in glands and ducts
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such as the salivary glands and the pancreas. They also form the walls of kidney tubules and the surface of the ovaries. Simple columnar epithelium is a single layer of tall, columnar cells lying on a basement membrane. These epithelia often form goblet cells, which are responsible for producing a lubrication mucus. Simple columnar epithelia line the entire digestive tract from the stomach to the anus. Epithelial membranes which are exposed to the body exterior are called mucus membranes. Stratified epithelia Stratified epithelial tissues are thicker than simple epithelial tissue due to the layering of cells upon one another. This arrangement is more durable, and thus these tissues provide a protective function. Stratified squamous epithelium is the most common stratified epithelial tissue. Although the free cells at the edge are squamous cells, those close to the basement membrane are often cuboidal or columnar. Stratified squamous epithelium is found at sites of high friction, such as the esophagus, the mouth and the outer portion of the skin. Stratified cuboidal and stratified columnar epithelia are rare in the human body. And usually, it is only the surface cells that fit this shape category, while the cells closer to the basement membrane vary in size and shape. These tissues are found mainly in the ducts of large organs. Transitional epithelium is a modified stratified squamous epithelium that forms the lining of the urinary system. These organs are subject to considerable stretching, and the stratified arrangement of the epithelial tissue facilitates this. The cells are able to slide past each other and change shape, to allow for distension of organs when filled with urine. Glandular epithelia A gland consists of one or more cells that make and secrete a particular product, called a secretion. Secretion is an active process whereby glands take in materials from the blood, manufacture them into a usable product, and discharge them. Two major gland types develop from epithelial tissues. Endocrine glands, also called ductless glands, lose their connection to the surface ducts. These are hormone producing glands such as the 14
thyroid, adrenal and pituitary glands. Their secretions diffuse directly into the blood vessels. Exocrine glands remain connected to their ducts, and secrete their products through the ducts to the epithelial surface. Exocrine glands can be both internal and external, and are found in the pancreas and liver, as well as sweat and oil glands.
Connective tissue Connective tissue connects body parts. As such, it is the most common and widely distributed of all body tissues. Connective tissues perform multiple functions, but are primarily concerned with protecting, supporting and binding together body tissues. Characteristics of connective tissue Connective tissues have the following characteristics: They have variations in blood supply. Although most connective tissues have good blood supply, meaning they are well vascularised, there are exceptions. Tendons and ligaments have poor blood supply, while cartilage is avascular. Connective tissues are made of many different types of cells, as well as non-living substances found outside of cells, called the extracellular matrix. The extracellular matrix is what makes connective tissue different from other tissues. The matrix is produced by the connective tissue cells and secreted to the exterior of the cell. Depending on the connective tissue type, the matrix may be liquid, semisolid or very hard. The extracellular matrix is what allows connective tissue to be able to bear weight and withstand stretching. The matrix also consists of various types and amounts of fibers. These include collagen fibers known as white fibers, elastic fibers known as yellow fibers, and reticular, or fine collagen, fibers. The fibers are made and secreted by the connective tissue cells. Connective tissue types are largely determined by the amount and type of fibers in the matrix. Bone Bone, or osseous tissue, is composed of bone cells sitting in cavities called lacunae. These cells are surrounded by a very hard matrix that contains calcium salts and large amounts of collagen fibers. Figure 5 describes what the bony tissue looks like when cells are removed: 15
Figure 5 Cartilage Cartilage is less hard and more flexible than bone, and is found in fewer locations throughout the body. The most common cartilage is hyaline cartilage, which has an abundance of collagen fibers hidden by a rubbery matrix. Hyaline cartilage forms the supporting structures of the larynx, attaches the ribs to sternum, and forms joints at the end of bones. Elastic cartilage is found where a structure with elasticity is needed, such as the ear. Fibrocartilage, which is highly compressible, forms the cushion-like discs between the vertebrae. Dense connective tissue Dense connective tissue is also known as dense fibrous tissue, has collagen fibers as its main matrix element. These fibers are produced by fibroblasts, which are fiber-forming cells found between the collagen fibers. Dense connective tissue forms strong, elongated structures such as tendons and ligaments, as well as the lower layers of the skin. Loose connective tissue Loose connective tissues are softer and have more cells and fewer fibers than most dense connective tissue. Two types of loose connective tissue exist: areolar tissue and adipose tissue. Areolar tissue is the most common connective tissue. It is the soft tissue that surrounds body organs. It functions as a packing tissue as 16
holds internal organs together and in position. A thin layer of areolar tissue underlies all mucous membranes. Areolar tissue has a loose, fluid matrix that contains all types of fibers. These fibers, however, are very loosely connected, giving the impression that the majority of them matrix is just empty space. Areolar tissue provides a storage facility of water and salts for surrounding tissues, and all body tissues obtain nutrients and release wastes into the areolar tissue. Figure 6 indicates what areolar tissue looks like:
Figure 6 Adipose tissue is commonly referred to as fat. It is essentially areolar tissue in which an abundance of fat cells are found. Adipose tissue forms the subcutaneous tissue beneath the skin, and is responsible for insulation of the body from both hot and cold temperatures. Adipose tissue surrounds and cushions some of the body’s organs, such as the kidneys and eyeballs. Blood Blood, or vascular tissue, is considered to be a connective tissue as it consists of blood cells surrounded by a non-living fluid matrix called blood plasma. The fibers of blood are soluble proteins that only become visible during blood clotting.
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Muscle tissue Muscle tissues are highly specialized tissues which contract to produce movement. Because muscle cells are elongated to provide a long axis for contraction, they are called muscle fibers. There are three types of muscle tissue known as skeletal muscle, cardiac muscle, and smooth muscle. Figure 7 shows what the different muscle tissue types look like:
Figure 7 Skeletal muscle Skeletal muscle cells are packaged by connective tissue into organs called skeletal muscles. Skeletal muscles can be consciously controlled, and are thus known as voluntary muscles. When skeletal muscles contract, they pull on the bones or skin. Gross body movements and changes in facial expression are the result of skeletal muscle contractions. The cells of skeletal muscles are long and cylindrical, with obvious stripes called striations. Cardiac muscle Cardiac muscle is only found in the heart. As it contracts, the heart pumps and forces blood through the blood vessels. Like skeletal muscle, cardiac muscle has striations. Cardiac muscle is not controlled consciously, and is therefore known as involuntary muscle. 18
Smooth muscle Smooth muscle, also known as visceral muscle, have no visible striations. The individual cells have a single nucleus and are pointed at each end. Smooth muscles are considered to be involuntary. Smooth muscle is found in the walls of hollow organs such as the stomach, bladder, uterus and blood vessels. When smooth muscle contracts, the organ cavity alternately constricts and dilates to propel substances through the organ. Peristalsis is a typical example of smooth muscle activity.
Nervous tissue Nervous tissue is made up of cells called neurons. All neurons conduct electrochemical impulses, and thus count irritability and conductivity as their major characteristics. The structure of neurons is adapted to allow single neurons to conduct an impulse over long distances through the body. One such adaptation is that the cytoplasm is stretched out into a long extension. Neurons, along with supporting cells that insulate, support and protect the neurons, form the structures that make up the nervous system. Figure 8 shows what nervous tissue looks like under the microscope:
Figure 8
Key takeaways • • • •
Cells have three major regions – the nucleus, cytoplasm and plasma membrane. The nucleus controls the cell and contains the DNA The cytoplasm houses the organelles and is where most cellular activity occurs The plasma membrane limits and encloses the cytoplasm and acts as a selectively permeable barrier. 19
• • •
• • • •
Epithelium is the covering, lining and glandular tissue whose functions include protection, absorption, and secretion. Epithelia are named according to cell shape and cell arrangement Connective tissue is the supportive, protective and binding tissue characterized by the presence of an extracellular matrix produced and secreted by the cells. Fat, ligaments, tendon, bones and cartilage are all connective tissues. Muscle tissue is specialized to contract or shorten to produce movement. There are three types of muscle tissue, known as skeletal muscle, cardiac muscle, and smooth muscle. Nervous tissue is made of cells called neurons that receive and transmit nerve impulses throughout the body.
Review questions Question 1 Which organelle is considered to be the control center of the cell? A. B. C. D.
The endoplasmic reticulum. The nucleus. The mitochondria The golgi apparatus
The answer is B, the nucleus. Question 2 Which of the following is not a function of DNA? A. B. C. D.
Provides a blueprint of instructions for the body. Provides a site for protein synthesis. Responsible for the building of proteins. Key role player in cell reproduction.
The answer is B, DNA does not provide a site for protein synthesis.
Question 3 When the cell is not dividing, DNA combines with protein to form a loose network of threads called the… A. B. C. D.
Chromatin Nucleoli Spindle fibers Chromosomes
The answer is A, DNA combines with protein to form chromatin. 20
Question 4 The outer limits of the cell are defined by… A. B. C. D.
The plasma membrane The cytoplasm The cytosol The endoplasmic reticulum
The answer is A, the plasma membrane. Question 5 Which constituent of cytoplasm is not a functional unit? A. B. C. D.
Cytosol Organelles Inclusions Plasma membrane
The answer is C, the inclusions. Question 6 Which organelle is responsible for the transport of substances between cells? A. B. C. D.
Endoplasmic reticulum Golgi apparatus Peroxisome Centrioles
The answer is A, the endoplasmic reticulum. Question 7 Which organelle is responsible for the digestion of worn out cell structures and foreign objects? A. B. C. D.
Mitochondria Peroxisomes Lysosomes Ribosomes
The answer is D, the ribosomes. Question 8 Which of the following is a function of epithelial tissue? A. B. C. D.
Protection Absorption Secretion All of the above
The answer is D, all of the above. 21
Question 9 Which characteristic of epithelial tissue is used to classify epithelia? A. B. C. D.
Arrangement Mobility Flexibility Attachment site
The answer is A, the epithelial arrangement. Question 10 Simple epithelia is thin, making it suitable for areas of filtration and substance exchange, as in the… A. B. C. D.
Alveoli of the lung Skin Esophagus Endocrine glands
The answer is A, the alveoli of the lung.
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