AP Lab Manual 2015 -16 vfinal by School of the Holy Child

Fascia and Sinew

School of the Holy Childâ&#x20AC;&#x2122;s Human Anatomy and Physiology Lab Manual Michael Clancy

Name:

Fascia and Sinew School of the Holy Childâ&#x20AC;&#x2122;s Human Anatomy and Physiology Lab Manual 2015-2016 Michael Clancy

Contents Lab Safety Guidelines

Exercise 1:

Protozoa Lab

Exercise 2:

Classification of Tissues

Exercise 3:

External Anatomy of the Rat

Exercise 4:

The Abdominal Cavity of the Rat

Exercise 5:

The Pelvic and Thoracic Cavities of the Rat

Exercise 6:

Beef Bone Examination

Exercise 7:

Chicken Wing Dissection

Exercise 8:

Sheep Brain Dissection

Exercise 9:

Somatic Reflexes

Exercise 10: The Cow Eye

Exercise 11: Visual Testing

Exercise 12: Pig Heart Dissection

Exercise 13: Pulse and Heart Sounds

Exercise 14: Blood Pressure

Exercise 15: External Anatomy of the Fetal Pig

Exercise 16: The Digestive System of the Fetal Pig

Exercise 17: The Cardiovascular and Respiratory Systems of the Fetal Pig

Exercise 18: The Digestive System of the Shark: Part 1

Exercise 19: The Digestive System of the Shark: Part 2

Exercise 20: The Digestive System of the Shark: Part 3

Exercise 21: Tactile Sensitivity

References

Lab Safety Guidelines 1. Know the locations of the following: fire extinguisher, fire blanket, chemical shower, eyewash station, first aid kit, and broken glassware containers. 2. Do not eat, drink, handle contact lenses, store food, or apply cosmetics or lip balm in the laboratory. 3. Always wear protective glasses, a lab apron, and disposable gloves during dissections. Cover open cuts or scrapes on your hands and fingers before donning gloves. 4. Wearing contact lenses in the laboratory is not advisable. They do not provide eye protection and may trap material on the surface of the eye. Soft contact lenses may absorb harmful chemicals. If possible, wear eyeglasses instead. 5. Never rub your eyes during a dissection. Inform Mr. Clancy immediately if you get anything in your eye during a dissection. 6. Restrain long hair, loose clothing, and dangling jewelry. It is recommended that you remove long-sleeve sweatshirts or sweaters prior to the lab. 7. If your tear a glove, wash your hands and get a new one. 8. Keep all glassware and dissecting materials away from the edge of lab tables. 9. Report all spills, broken glassware, or accidents, no matter how minor, to Mr. Clancy. 10. If you begin to feel ill or light-headed, immediately step out of the lab. 11. Wash your hands with soap and water before leaving the lab.

At the end of each dissection: •

Place all tools in the soapy water container.

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Rinse the dissecting tray in the sink.

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Dispose of gloves and organic materials in the designated trash container.

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Wipe down the lab table with a wet sponge and table cleaner.

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Wash your hands thoroughly with soap and water.

Dissecting tools of the trade. From left: scalpel, forceps, scissors, blunt probe, dissecting needle.

Dissecting Tools 1. Scalpel: When most students think of dissecting, they imagine wielding a scalpel much of the

time. In truth, the scalpel is a seldom-used tool. Dissecting scissors offer more precision, particularly with delicate organs and membranes and hard-to-reach areas. A scalpel may be used to gently scrape away connective tissue and fat, cut through tough fibrous tissues, and make small incisions. Of all the tools, the scalpel demands the most caution; not only can its blade cut your finger very quickly, it can also easily damage the specimen. Use it carefully and sparingly. 2. Forceps: The ends of a forceps can be either blunt or pointed, and the gripping surfaces are

grooved. They are used to grasp small objects and to remove or pull away connective tissue. Never refer to them as tweezers! 3. Scissors: Dissecting scissors are usually four to six inches long. They come in a variety of

shapes: both blades pointed, both blades rounded, and one blade pointed with the other blade rounded. We will use the pointed variety, as they offer the greatest precision. Scissors are used to cut through skin, to cut muscles through their center (bisect), and to make other large, clean cuts through major organs. 4. Blunt Probe: This tool is a rigid five-inch steel instrument with a blunt and bent tip. It is very

useful for tearing through connective tissue and teasing membranes and muscles apart. You can also use it to separate fragile structures from their attachments. This is my favorite dissecting tool! 5. Dissecting Needle: This tool is useful for isolating very small parts.

Exercise 1: Protozoa Purpose: When you have finished this exercise, you will be able to: 1. Identify Paramecium, Stentor, Euglena, Spirostomum, and Blepharisma. 2. Summarize and compare the structures of each of these organisms. Introduction: What if all you have is one cell? We humans have a mouth to eat with, a digestive system to process our meals and snacks, and a cardiovascular system to transport materials to and from our various parts. There is an urinary system to rid us of our cell wastes, and we have muscles to move parts of our bodies. We have a nervous system that coordinates all of these activities and enables us to respond to changes in our environment. All of these functions can be accomplished due to the many different types of cells found in our bodies. While many organisms are multicellular, there are others that are unicellular, carrying on all of lifeâ&#x20AC;&#x2122;s activities within the space of just one cell. Many of these one-celled organisms are grouped together into a very large category called the Kingdom Protista and are themselves described as protists. Protists are found world-wide, living wherever there is moisture. They exhibit different life styles. Some, for example, contain chlorophyll and can make their own food. Others ingest (take in) and digest their own food. Some can even switch from one mode of nutrition to the other. Most live singly while others live in colonies. In your work today, you will be examining five types of protists. Materials: Compound microscope Protozoa demoslides Procedure: 1. Working with your partner, visit each of the five microscope stations. Carefully observe and draw the protozoa you see under each microscope.

2. Make a drawing of each protozoa demoslide. You may see hundreds of protozoa in one slide; you only need to draw one or two of each. 3. Be sure to correctly label each drawing you make. 4. When you have observed and drawn each of the specimens, answer the questions that follow. You may discuss them with your partner. A. Paramecium Things to notice: •

Cilia: These tiny, hair-like structures cover the entire cell surface like a carpet. The cilia move back and forth to propel the paramecium through the water. If you cannot see the cilia, look for their effect on the material in the water around the organism.

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Oral groove: This is a depression on one side of the organism through which food is taken in.

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Food vacuole: Ingested food is sealed off in this structure. Other parts of the cell digest the food.

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Nucleus: This is a large oval structure that controls all cell activities.

Name: Paramecium Magnification:

Question 1: What happened when a paramecium bumped into something? ______________________________________________________________________________ Question 2: Which is the front of the paramecium, the blunt end or the pointed end? Support your response. ______________________________________________________________________________ ______________________________________________________________________________ B. Euglena Things to notice: â&#x20AC;˘

Chloroplasts: These structures contain chlorophyll, a substance you will learn about during the year. Photosynthesis occurs here.

â&#x20AC;˘

Flagellum: This is a whip-like structure that moves the Euglena.

Name: Euglena Magnification:

Question 3: One of the first things to observe about Euglena, even without using a microscope, is the green color. What pigment is present in Euglena that you think accounts for this color? _______________________________ Question 4: Why is the presence of this pigment significant in how these organisms live? ______________________________________________________________________________ ______________________________________________________________________________ Question 5: How is Euglena like a plant? How is it like an animal?

__________________________________________________________________ __________________________________________________________________ 5

C. Stentor Things to notice: •

Stentor is a ciliated, trumpet-shaped protist. Although it can swim rapidly, when ingesting food it “sits down” with its base attached to an object in the water.

•

During feeding the Stentor stretches out and vibrates a circle of large cilia so rapidly they resemble a spinning wheel. This motion produces a current that sweeps food particles into the gullet.

Name: Stentor Magnification:

D. Spirostomum Things to look for: •

Spirostomum are among the largest and most complex single-celled protists.

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Spirostomum can contract faster than any other living cell.

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Its body has spiral rows of cilia. These cilia beat back and forth top move the organism with a snakelike wiggling motion. Beating cilia also sweep food into the spirostomum’s mouth.

Name: Spirostomum Magnification:

E. Blepharisma Things to look for: •

Blepharisma is notable in the protist world for its unusual color. Unlike most protists, it is a faint shade of pink.

•

At room temperature these organisms tend to move quickly, making them difficult to view their activities (and even more difficult to draw).

Name: Blepharisma Magnification:

Question 7: Based on what you observed in today’s lab, label each of the organisms below:

____________ ____________ ____________ ____________ ____________

Exercise 2: Classification of Tissues Purpose: When you have finished this exercise, you will be able to distinguish among the four basic types of body tissues and identify examples of each. Introduction Cells are the building blocks of all living things. In humans and other multicellular organisms, cells depend on one another and cooperate to maintain homeostasis in the body. With a few exceptions, even the most complex animal starts out as a single cell: the fertilized egg, which divides almost endlessly. The trillions of cells that result then specialize for a particular function. Some become supportive bone, others nerve cells, and so on. Thus, a division of labor exists, with certain groups of cells highly specialized to perform functions that benefit the organism as a whole. Cell specialization provides for sophisticated functions but has certain hazards, because when a small, specific group of cells is indispensable, any inability to function on its part can paralyze or destroy the entire body. Groups of cells that are similar in structure and function are called tissues. There are four primary tissue types: epithelial, connective, muscular, and nervous. Each has distinct structures, patterns, and functions. To perform specific body functions, tissues are organized into organs such as the kidneys, heart, and lungs. Most organs contain all four types of tissues. In this lab, we will examine a sampling of the four main types of tissues. Materials: Compound microscope, slide collection of epithelial, connective, muscle, and nerve tissues Procedure: Use a compound microscope to view all of the tissue types that follow. Make a color sketch of each slide you look at. Be sure to include the magnification. 1. Epithelial Tissue Epithelial tissue, or epithelium, covers surfaces. For example, epithelia cover the external body surface (as in the epidermis), line body cavities, and generally mark off our “insides” from our “outsides.” Because most glands of the body develop from epithelial membranes, they too are classified as epithelia.

The functions of epithelial tissue include protection, absorption, filtration, and excretion. For example, your skin protects you from bacterial invasion and chemical damage. Another example of this tissue’s protective nature can be found in the respiratory tract, where the lining is ciliated to sweep dust and other particles away from the lungs. Epithelia generally exhibit the following characteristics: •

Cells that fit closely together to form membranes (sheets of cells).

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The membranes always have one exposed surface or free edge, called the apical surface.

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Epithelial cells have no blood supply of their own (the term for this is avascular), and depend on the diffusion of nutrients from the underlying connective tissue.

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If well nourished, epithelial cells can easily regenerate themselves. This is an important characteristic because many epithelia are subjected to a good deal of friction and other types of trauma.

The covering and lining epithelia are classified according to two criteria: cells shape (height) and the relative number of layers. Squamous (scalelike), cuboidal (cubelike) and columnar (column-shaped) epithelial cells are the general types based on shape. On the basis of layers, there are simple epithelia (consisting of one layer of cells attached to the basement membrane), and stratified epithelia, consisting of more than one layer of cells with only the deepest layer resting on the basement membrane. A. Simple Squamous Epithelium Description: a single layer of flattened cells with disc-shaped central nuclei; the simplest of the epithelia. Location: air sacs of lungs, lining of heart and blood vessels, lining of ventral body cavity. Function: allows passage of materials by diffusion and filtration; may secrete lubricating substances. Slide: _________________________________ Magnification: _______________

B. Simple Cuboidal Epithelium Description: a single layer of cubelike cells with large, spherical central nuclei. Location: ducts of small glands, kidney tubules, surface of ovaries. Function: secretion and absorption.

Slide: _________________________________ Magnification: _______________

C. Simple Columnar Epithelium Description: a single layer of tall cells with oval nuclei; some cells have cilia; layer may contain mucus-secreting goblet cells. Location: Nonciliated type lines most of the digestive tract (stomach to anal canal) and gallbladder; ciliated variety lines small bronchi in lungs and uterine tubes. Function: absorption, secretion of mucus, enzymes, and other substances; ciliated type propels mucus by ciliary action.

Slide: _________________________________ Magnification: _______________

D. Stratified Squamous Epithelium Description: thick membrane composed of several cell layers; in the keratinized type, surface cells are full of keratin and dead; the basal cells are active in mitosis and produce cells for the more superficial layers. Location: epidermis of skin; lining of mouth, esophagus, and vagina. Function: protects underlying tissues in areas subjected to abrasion.

Slide: _________________________________ Magnification: _______________

2. Connective Tissue Connective tissue is found in all parts of the body. In fact, it is the most abundant and widely distributed of the tissue types. Connective tissues perform a variety of functions, but they primarily protect, support, and bind together other tissues of the body. For example, your bones are composed of connective tissue (osseous tissue), and they protect and support other body tissues and organs. Ligaments and tendons (dense regular connective tissue) bind the bones together or attach skeletal muscles to bones. Connective tissue also serves a vital function in the repair of all body tissues; many wounds are repaired by connective tissue in the form of scar tissue. Connective tissues are composed of many types of cells, and there is a great deal of nonliving material between the cells. This nonliving material, called the extracellular matrix, distinguishes connective tissue from all other tissues. The matrix is primarily responsible for the strength associated with connective tissue, but its firmness and relative amount vary. There are several types of connective tissue, all of which typically have large amounts of matrix. These are the loose connective tissues (which include areolar, adipose, and reticular), dense (fibrous) connective tissue, cartilage, bone, and blood. A. Areolar Connective Tissue Description: gel-like matrix; cells include fibroblasts (fiber-forming cells), phagocytes, some white blood cells. Location: widely distributed under epithelia of body; packages organs and surrounds capillaries. Function: Wraps and cushions organs; phagocytes engulf bacteria; plays an important role in inflammation; holds and conveys tissue fluid. Slide: _________________________________ Magnification: _______________

B. Adipose Tissue Description: contains a matrix as in areolar, but very sparse; closely packed fat cells; nuclei are pushed to the side by large fat droplets. Location: under skin; around kidneys and eyeballs; within abdomen and breasts. Function: provides reserve food fuel; insulates against heat loss; supports and protects organs.

Slide: _________________________________ Magnification: _______________

C. Bone (Osseous) Tissue Description: hard, calcified matrix containing many collagen fibers; very well vascularized. Location: bones. Function: supports and protects (by enclosing); provides levers for muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation. Slide: _________________________________ Magnification: _______________

3. Muscle Tissue Muscle tissue is specialized to contract (shorten) to provide movement of some body parts. As you might expect, muscle cells are elongated to provide a long axis for contraction. The three basic types of muscle tissue are: •

Skeletal muscle: the “meat” or “flesh” of the body is attached to the skeleton. It is under voluntary control, meaning that you can control it consciously, and as it contracts it moves the limbs and other external body parts. The cells of skeletal muscles are long, cylindrical, and multinucleate (several nuclei per cell); they have obvious striations (stripes) when viewed under a microscope.

•

Cardiac muscle: found only in the heart. As it contracts, the heart acts like a pump, propelling the blood into the blood vessels. Like skeletal muscle, cardiac muscle has striations, but cardiac cells are branching cells with one nucleus (or occasionally two) that fit together at junctions called intercalated discs that allow cardiac muscle to move as a unit. Cardiac muscle is under involuntary control, which means that we cannot voluntarily or consciously control the operation of the heart.

•

Smooth muscle: found mainly in the walls of hollow organs (digestive and urinary tract organs, uterus, blood vessels). Smooth muscle is nonstriated (no stripes) and involuntary, and it is made of cells that are spindle-shaped with one nucleus. 13

A. Skeletal Muscle Description: long, cylindrical, multinucleate cells; obvious striations. Location: in skeletal muscles attached to bones or occasionally the skin. Function: voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control. Slide: _________________________________ Magnification: _______________

B. Cardiac muscle Description: branching, striated, generally uninucleate cells that connect at junctions called intercalated discs. Location: the walls of the heart. Function: as it contracts, it propels blood into the circulation; involuntary control. Slide: _________________________________ Magnification: _______________

C. Smooth muscle Description: spindle-shaped cells with central nuclei; cells arranged closely to form sheets; no striations. Location: mostly in the walls of hollow organs. Function: propels substances or objects (food, urine, a baby) along internal passageways; involuntary control. Slide: _________________________________ Magnification: _______________

4. Nervous Tissue Nervous tissue is composed of two major cell populations. Neurons are highly specialized to receive stimuli and to conduct impulses to all parts of the body. They are the cells that are most often associated with nervous system functioning. Neuroglia are special supporting cells that protect, support, and insulate the more delicate neurons. The structure of neurons is markedly different from that of other body cells. They all have a nucleus-containing cell body, and their cytoplasm is drawn out into long processes (called cell extensions)--sometimes as long as 3 feet--which allows a single neuron to conduct an impulse over relatively long distances. Description: neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body. Nonirritable supporting cells also contribute to nervous tissue. Location: brain, spinal cord, and nerves. Function: transmit electrical signals from sensory receptors and to effectors (muscles and glands) which control their activity. Slide: _________________________________ Magnification: _______________

Exercise 3: External Anatomy of the Rat Purpose: When you have finished this exercise, you will be familiar with the external anatomy of the rat. Introduction: The recent history of the rat is a story of survival that parallels the development of human civilizations. The species we identify as the common rat and its larger cousin, the Norway rat, originated from their natural habitat in Southeast Asia. From there they emigrated to China, Europe, Africa, and eventually to America. Their means of dispersal was via humans, with whom they formed a commensal relationship (a symbiotic relationship in which one organism benefits without causing major harm to the other). The successful survival of the rat was the result of several factors, including a high rate of reproduction, an incredible ability to adapt to different environments, and a knack for feeding opportunistically on the discards of human civilization. In todayâ&#x20AC;&#x2122;s world, the rat has become an established member of the global community and has had a significant impact on human beings. Many of the numerous tiny organisms rats carry spread disease among human populations, and their feeding on agricultural stores results in a significant reduction of food that would otherwise be available for human consumption. On a more positive note, the rat has provided us with important opportunities for scientific progress. Its anatomical and physiological resemblance to humans as mammals, coupled with its high reproductive rate and ease of maintenance in the laboratory, has made it an invaluable research specimen. The abundance of the rat has also made it a convenient specimen for student dissections. It provides us with a firsthand look at a typical small mammal. The experience has merit, as it gives us an opportunity to examine real structures and develop surgical skills. Materials: preserved rat, dissecting tray, string, gloves, goggles, apron Procedure: 1. Place the rat on the dissecting tray ventral (belly) side up. Notice that its body, like that of other mammals, consists of body regions that include a head, neck, trunk, limbs, and tail. 2. Identify and examine the following features: â&#x20AC;˘

Head: contains the pinnae (external ears), the eyes, and the nostrils (external nares) on the rostrum. Also notice the vibrissae or whiskers that arise from the cheeks,and the nictitating membrane that originates in the lower medial corner of the eye.

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Trunk: includes a thoracic region (or thorax), a middle abdominal region, and a caudal pelvic region. Identify the external openings to the mammary glands, or teats. In the rat, there are usually six pairs of teats distributed along the ventral thorax and abdomen.

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External genitals: located caudal to the hind legs. If you have a male, observe the small rod-shaped penis and nearby sac of skin, the scrotum. The scrotum contains the gonads, the testes. If you have a female rat, observe that the urinary and reproductive openings are separated; the ventral opening is the urethral orifice, and the dorsal opening is the vaginal orifice. In the rat and most other mammals, the opening to the digestive tract is separate from the urinary and reproductive openings. This is the anus and is located near the ventral base of the tail in both sexes.

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Limbs: as a typical quadruped mammal, the rat has four limbs: two upper limbs (or forelimbs) and two lower limbs (or hind limbs).

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Tail: the tail of a rat is quite long, often nearly as long as the trunk. It is sparsely covered with hair. Note the scalelike texture of the skin surface.

3. Make a drawing of your rat, labeling all terms in boldface above. 4. Place your rat in the plastic bag. Make sure you and your partner’s names are on it.

Figure 1: Dorsal view of the rat’s head.

Head Region

Thoracic Region

Abdominal Region

Figure 2: Ventral view of the rat.

Exercise 4: The Abdominal Cavity of the Rat Purpose: When you have finished this exercise, you will be able to identify the abdominal organs of the rat. Materials: preserved rat, dissecting tray, string, forceps, scalpel, scissors, blunt probe, gloves, goggles, apron Procedure 1. Secure your specimen ventral side up to the dissecting tray. 2. Lift the abdominal skin with a forceps just above the urethral orifice and snip through it with a scissors. Carefully cut through the muscles of the abdominal wall, avoiding the underlying organs. Remember: to dissect means â&#x20AC;&#x153;to separateâ&#x20AC;?â&#x20AC;&#x201D;not mutilate. Hold and lift the muscle and skin layers with a forceps and cut from the pubic region to the bottom of the rib cage (cut #1 in figure 1). Make two lateral cuts just beneath the rib cage (cuts #2 and #3). Look for a thin membrane attached to the inferior boundary of the rib cage; this is the diaphragm, which separates the thoracic and abdominal cavities and is the main muscle for breathing. 3. Make two similar lateral cuts near the hind legs (cuts #4 and #5). Pull the flaps of the abdominal wall back to expose the abdominal cavity. If necessary, pin the flaps to your dissecting tray.

Figure 1

4. Note the following organs of the abdominal cavity: a. Liver: a prominent, dark-brown organ located beneath the diaphragm, with most of its bulk on the right side. Like the human liver, the rat’s liver has four lobes: the large medial lobe, a right lateral lobe, a left lateral lobe, and a small caudal lobe. Among other things, the liver produces bile for the digestion of fats. Note that there is no gallbladder for bile storage in the rat as there is in most other mammals, including humans. b. Stomach: a J-shaped enlargement of the digestive tract, located directly beneath the diaphragm on the left side of the abdominal cavity. It serves as a temporary storage pouch for swallowed food, and its inner lining contains gastric glands that secrete hydrochloric acid and enzymes to begin the digestion of protein. c. Spleen: a flat, elongated dark red organ near the dorsolateral (what do you think this means?) surface of the stomach. The spleen is part of the lymphatic system. d. Small Intestine: a long, winding tube that extends from the pyloric sphincter of the stomach to its junction with the large intestine. It is roughly six times the length of the rat from snout to tail. The small intestine completes chemical digestion and is the site for most nutrient absorption into the bloodstream. Similar to the human small intestine, the small intestine of the rat is divided into three segments: the duodenum, the jejunum, and the ileum. e. Large Intestine: The caudal portion of the digestive tract, the large intestine extends from the ileocecal valve to the anus. It absorbs water from the undigested or unabsorbed food from the small intestine, forming feces. The large intestine is divided into the cecum, colon, and rectum: • Cecum: the cranial segment which communicates with the ileum via the ileocecal valve. The cecum is a large, blind sac that projects caudally and can be identified by its thin walls and large diameter (which exceeds that of other segments of the large intestine). At its terminal end, a narrow, thicker-walled extension is present, the vermiform appendix. Compared to the rat’s appendix, the human appendix is proportionately very small. • Colon: a long, wide segment extending from the cecum to the rectum. The rat’s colon consists only of the ascending and descending sections; the human colon contains the ascending, transverse, descending, and sigmoid sections. • Rectum: the terminal segment of the large intestine. It serves as a temporary storage area for feces. f. Pancreas: You may have to lift the stomach to see this soft glandular organ. The pancreas secretes hormones that regulate blood sugar levels, along with powerful digestive enzymes into the duodenum. Unlike the human pancreas, which is a single structure, the rat’s pancreas consists of two portions: the dorsal pancreas and the ventral pancreas.

5. Make a detailed sketch of your rat, labeling or organs that appear in bold.

Liver

Small Intestine

Figure 2: The organs that will immediately be visible to you as you open the abdominal cavity wall are the dark red liver and small intestine.

Exercise 5: The Pelvic and Thoracic Cavities of the Rat Purpose: When you have finished this exercise, you will be able to identify the pelvic and thoracic cavity organs of the rat. Materials: preserved rat, dissecting tray, string, forceps, scalpel, scissors, blunt probe, gloves, goggles, apron Procedure: 1. Secure your specimen ventral side up to the dissecting tray. 2. The peritoneum is the extensive serous membrane of the abdominopelvic cavity, which you initially observed when you opened up the cavity (I described it as â&#x20AC;&#x153;clear plastic wrapâ&#x20AC;?). Serous membranes are constructed of two layers. The parietal layer lines a specific portion of the wall of the ventral body cavity. It folds onto itself to form the visceral layer, which covers the outside of the organs in that cavity. These layers are separated not by air, but by a thin, clear liquid, called serous fluid, that is secreted by both membranes. The serous fluid allows the organs to slide easily across the cavity walls and one another with little friction as they carry out their routine functions. There are three extensions of the peritoneum you should attempt to find: a. Falciform ligament: a double-layered extension of the visceral peritoneum of the liver. It secures the liver to the dorsal wall of abdomen and diaphragm. You many find it difficult to see. b. Mesentery: a double layer of peritoneum that connects the small and large intestines to the dorsal abdominal wall. c. Greater Omentum: a double layer of the visceral peritoneum that extends from the greater curvature of the stomach caudally, appearing somewhat like an apron. 3. Carefully lift out the mass of organs in the abdominal cavity. This will allow for a better view of the intestines and should allow you to see some of the organs that were described but obscured in the previous lab: a.

Small Intestine: a long, winding tube that extends from the pyloric sphincter of the stomach to its junction with the large intestine. It is roughly six times the length of the rat from snout to tail. The small intestine completes chemical digestion and is the only site for nutrient 25

absorption into the bloodstream. Similar to the human small intestine, the small intestine of the rat is divided into three segments: the duodenum, the jejunum, and the ileum. b. Large Intestine: Recall that the cecum is the portion of the large intestine that connects with the small intestine. It is a large sac. From its terminal end you may find the vermiform appendix. c.

Colon: a long, wide segment of the large intestine extending from the cecum to the rectum.

d. Rectum: the terminal segment of the large intestine. The short rectum opens to the exterior via the anus, which is surrounded by sphincter muscles. 4. Insert one blade of your dissecting scissors under the ribcage at the midline. Lift the blade as you carefully cut through the ribs toward the head until you reach the neck. Make two lateral cuts near the forelimbs to expose the thoracic cavity (see figure 2). Observe, but do not draw, the following organs:

Stomach

Figure 1: The stomach is clearly visible after the liver is removed.

a. Thymus: an endocrine gland that covers the heart. b. Heart: medial oval structure that lies between the lungs. c. Lungs: large, multi-lobed structures located lateral, cranial, and caudal to the heart d. Trachea: a tubular passageway formed by smooth muscle and connective tissue and supported by rings of cartilage. These rings keep the trachea open at all times. 5. Make a drawing of the organs listed in bold print above. Label only those that you actually see.

Trachea

Heart Right lung

Figure 2: The thoracic cavity

Exercise 6: Beef Bone Examination Purpose: When you have finished this lab, you will be able to identify the major structures of a long mammal bone. In addition, you will be able to distinguish between living and nonliving parts of osseous tissue. Materials: cow femur, dissecting kit, dissecting tray, safety goggles, apron, gloves, microscope, slide of osseous tissue Procedure: A. Examining a long bone 1. Referring to figure 1, identify the shaft, or diaphysis. Observe its smooth surface composed of compact bone. Look for the periosteum, a fibrous membrane that covers the bone surface. Notice that many fibers of the periosteum, called Sharpeyâ&#x20AC;&#x2122;s fibers, penetrate the bone. 2. Inspect the epiphysis, the end of a long bone. Notice that it is composed of a thin layer of compact bone enclosing spongy bone. 3. Identify the articular cartilage, which covers the epiphyseal surface in place of the periosteum. Because it is composed of glassy hyaline cartilage, it provides a smooth surface to prevent friction at joint surfaces.

Figure 1

4. If the animal was still young and growing, you will be able to see the epiphyseal plate, a thin area of hyaline cartilage that provides for growth in bone length. When long bone growth ends, these areas are replaced with bone. Their barely visible remnants are called epiphyseal lines. 5. In an adult animal, the medullary cavity, the central cavity of the shaft, is essentially a storage region for adipose tissue, or yellow marrow. In an infant, red marrow, involved in forming blood cells, is found in these central marrow cavities. In adults, red marrow is confined to the interior of the epiphyses. 6. Look carefully to see if you can distinguish the delicate endosteum lining the medullary cavity. 7. Make a sketch of the bone you examined on the following page, labeling the parts indicated in bold. B. Examining the microscopic structure of compact bone 1. Examine a prepared slide of ground bone under low power. Using figure 2 as a guide, focus on the Haversian (central) canal, which is indicated by the microscope pointer. The central canal runs parallel to the long axis of the bone and carries blood vessels and nerves through the bony matrix. Identify the the lacunae (chambers) where the osteocytes (mature bone cells) are found in living bone. These are arranged in concentric circles called lamellae around the central canal. A central canal and all of the lamellae surrounding it are referred to as an osteon. Also try to identify canaliculi, tiny canals running from a central canal to the lacunae of the first lamella and then from lamella to lamella. The canaliculi connect all the living cells of the osteon to the nutrient supply.

Haversian canal

Figure 2

2. Make a sketch of the bone slide you observed on the following page, labeling all of the bold faced words above that you were able to find.

Sketch of Long Bone

Sketch of Osseous Tissue Slide

Slide: _______________________________ Magnification: _______________

Exercise 7: Chicken Wing Dissection Purpose: To examine the relationships among muscles, bones, tendons, and ligaments Materials: chicken wing, dissecting tray, forceps, scissors, soap Procedure: 1. Insert a scissor point under the skin of the wing at its upper end and cut to the first joint. Be careful not to cut any muscle. Use your scissors, forceps, and fingers to remove as much skin from the upper and middle sections of the wing as you can. 2. Gently loosen the connective tissue around one large muscle in the middle section of the wing. Each end of the muscle narrows where it attaches to a tendon. Question 1: Where does the other end of the tendon attach? _____________________________ _____________________________________________________________________________ 3. Gently pull on the muscle. This shows what happens to a living chicken when this muscle shortens or contracts. 4. In the space below, make a sketch of the muscles, tendons, and bones you see.

5. Hook your index finger under the muscle. Slowly but firmly pull the muscle away from the bone. Question 2: Where did it tear: the muscle or the tendon? _______________________________ 6. Remove the tissue from around the joint. See if you can find ligaments. 7. Attempt to pull the bones apart at the joint. Pull, donâ&#x20AC;&#x2122;t twist! 8. Examine the cartilage at the end of the bone. 9. Complete the table below: Color

Texture

Other tissues it attaches to

Bone Tendon Cartilage Ligament

10. Thoroughly clean your hands, table, tools, and tray with soap and water. Question 3: Compare ligaments with tendons. List two ways they are similar and two ways they are different. _____________________________________________________________________________ _____________________________________________________________________________ Question 4: Compare the bones of a chicken wing with those of a human arm by examining the diagram below. List three ways they are similar and three ways they are different. _____________________________________________________________________________ _____________________________________________________________________________

bbachman.wikispaces.com

Exercise 8: Sheep Brain Dissection Purpose: After completing this lab, you will be able to identify and describe the major regions and features of the brain. Materials: sheep brain, scalpel, scissors, dissecting tray, apron, gloves, goggles Procedure: 1. Place your sheep brain so that you are viewing its lateral aspect. Compare the various areas of the sheep brain (cerebrum, brain stem, cerebellum) to the picture of the human brain in figure 1.

Cerebrum

Cerebellum Brain stem Figure 1: The human brain

Question 1: Relatively speaking, which of these structures is obviously much larger in humans? ______________________________________________________________________________ 2. Examine the superior surface of the brain. Notice that, like the human brain, its surface contains convolutions (sulci, or fissures and gyri, or hills). The sulci of a human brain are deeper than those of a sheep brain. Question 2: Given your understanding of surface area as learned throughout the year, why do you think this is so? ______________________________________________________________________________ ______________________________________________________________________________

3. Turn the brain over so that the ventral surface is up. Look for the club-like olfactory bulbs on the inferior surface of the frontal lobes of the cerebral hemispheres. (They may have been removed.) Question 3: What sense does olfactory pertain to? Use your textbook or an online resource to find out. ______________________________________________________________________________ Question 4: Is the sense of smell more important as a protective and food-getting sense in sheep or in humans? Support your response. ______________________________________________________________________________ ______________________________________________________________________________ 4. Compare your sheep brain with figure 2 below. Try to identify as many of the structures as you can. Again, some of the structures may no longer be present.

Optic chiasma Medulla oblongata

Spinal cord Olfactory bulb Pons

Optic nerve

5. Carefully examine the cerebellum. Notice that, in contrast to the human cerebellum, it is not divided longitudinally, and that its fissures are oriented differently. Observe the tree-like arrangement of its white matter. Question 5: What is this white matter called? ________________________________________ 6. Proceed to the lab table that contains midsagittal sections of the sheep brain. Using figure 3 as a guide, identify the structures listed below. 36

Cerebral hemisphere

Cerebellum

Corpus callosum

Pineal body

Spinal cord

Olfactory bulb Thalamus Optic chiasma

Hypothalamus

Pons

Medulla Fourth ventricle

Figure 3: Sagittal section of sheep brain

Question 6: Use your textbook or online resources to write a brief description of the function of the following structures: a. thalamus: ___________________________________________________________________ b. hypothalamus: _______________________________________________________________ _____________________________________________________________________________ c. midbrain: ___________________________________________________________________ d. pons: _______________________________________________________________________ e. medulla oblongata: ____________________________________________________________ ______________________________________________________________________________ f. third and fourth ventricles: ______________________________________________________ ______________________________________________________________________________ g. spinal cord: __________________________________________________________________ h. corpus callosum: _____________________________________________________________ 7. On a sheet of paper, make three drawings of the brains you have observed: dorsal, ventral, and sagittal views. In your drawings, label all of the parts that appear in bold in this packet. 8. Mr. Clancy has set up a station with a transverse section of the brain and spinal cord. Examine each specimen and identify the gray and white matter. Make a sketch of what you see and label the gray and white matter.

Exercise 9: Somatic Reflexes Purpose: During this lab you will learn to test for various reflexes in the body. Materials: reflex hammer, penlight Introduction: The Reflex Arc Neurons communicate in many ways, but much of what the body must do everyday is programmed as reflexes. Reflexes are rapid, predictable, involuntary motor responses to stimuli, and they occur over neural pathways called reflex arcs. Reflexes can be classified as either autonomic or somatic. Autonomic (or visceral) reflexes are not subject to conscious control. These reflexes activate smooth muscles, cardiac muscle, and the glands of the body that regulate body functions such as digestion and blood pressure. Somatic reflexes include all reflexes that stimulate skeletal muscles. An example of such a reflex is the rapid withdrawal of your hand from a hot surface. There are many types of somatic reflexes, several of which you will attempt to induce during this lab: the stretch, superficial cord, corneal, and gag reflexes. Some require only spinal cord activity, while others require brain involvement. Stretch reflexes are important postural reflexes that act to maintain posture, balance, and locomotion. Stretch reflexes are produced by tapping a tendon, which stretches the attached muscle. This stimulates muscle spindles (special sensory receptors in the muscle) and causes a reflex contraction of the stretched muscle, which resists further stretching. Even as the primary stretch reflex is occurring, impulses are relayed to higher brain centers to advise of muscle length and speed of shorteningâ&#x20AC;&#x201D;information needed to maintain muscle tone and posture. Reflex tests are used clinically to evaluate the nervous system and diagnose an abnormality or dysfunction that may cause an inhibition, exaggeration, or absence of reflexes. For each of the reflex tests that follow, evaluate each result using the following ratings: 0 = no response +1 = little response +2 = normal response +3 = above normal response +4 = exaggerated response 39

Procedure: A. Patellar (knee-jerk) reflex 1. Have your lab partner sit on the lab table with her legs hanging free. 2. Tap the patellar ligament sharply with the reflex hammer just below the knee to obtain a response (see figure 1). The knee-jerk hammer reflex assesses the L2-L4 level of the spinal cord. Test both knees and record your results. Left knee: _____________________

Right knee: _____________________

Figure 1: Morgan Bryant ’14 tests the patellar reflex response from Caroline O’Neill ’14.

3. Fatigue affects the patellar reflex response. Have your partner jog in place until her legs are tired (really tired—no slackers!). Test the patellar reflex again and record your response. Was it more or less vigorous than the first test? Left knee: _____________________

Right knee: _____________________

B. The Achilles (ankle jerk) reflex 1. Have your partner remove her shoe. 2. Hold your partner’s foot on the bottom with one hand. Dorsiflex her foot slightly (bring her toes slightly toward her knee) to increase the tension of the gastrocnemius (calf) muscle.

3. Sharply tap your partner’s Achilles tendon with the reflex hammer (see figure 2). Repeat for the other ankle. The ankle-jerk reflex assesses the first two sacral segments of the spinal cord. Record your results. Left ankle: _____________________

Right ankle: _____________________

Figure 2: Morgan Bryant ’14 tests the Achilles reflex response from Caroline O’Neill ’14.

C. The Plantar reflex The plantar reflex is an important neurological test. It is found by stimulating the cutaneous receptors in the sole of the foot. Stimulation of these receptors normally causes the toes to flex (curl) and move closer together. Damage to the corticospinal tract, a major voluntary muscle tract, produces what is known as Babinski’s sign, an abnormal response in which the toes flare and the big toe moves upward. (In newborns, Babinski’s sign is seen because the nervous system is not yet completely myelinated). 1. Have your partner remove a shoe and carefully lie on a lab table. Her knees should be slightly bent, and her thighs should be rotated so that the sides of her feet rest on the table. 2. Move the handle of the reflex hammer firmly up the lateral side of the sole from the heel to the base of the big toe (see figure 3). Repeat with the other foot and record your results Left foot: _____________________

Right foot: _____________________

Was this a normal plantar reflex of Babinski’s sign? What is your evidence? _____________________________________________________________________________

Figure 3:Testing the plantar reflex.

D. Pupillary Reflex When photoreceptors in the retina are stimulated by light, nerve impulse are sent via the optic nerve to integrating centers in the brain. Interneurons from these centers send impulses to the midbrain, which instantly relays a message to smooth muscles in the iris of the eye. When these muscles contract, the pupil constricts. 1. Conduct the testing in an area where the lighting is relatively dim. 2. Approximate the size of your partnerâ&#x20AC;&#x2122;s pupils in millimeters as best you can. Right pupil: _____________ mm

Left pupil: _____________ mm

3. Stand to the left of your partner to conduct the testing. Your partner should shield her left eye by holding a hand vertically between the right eye and the side of the nose. 4. Using a quick right-to-left motion, shine the penlight into your partnerâ&#x20AC;&#x2122;s right eye. What is the pupillary response? Explain the value of this reflex. _____________________________________________________________________________ _____________________________________________________________________________ 5. Observe the left pupil while shining the penlight on the right pupil. Has the same type of change (called a consensual response) occurred in the left eye? Why do you think this happens? _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________

Exercise 10: The Cow Eye Purpose: During this activity you will observe the structures of the eye and note their functions. Materials: cow eye, dissecting tray, dissecting kit, goggles, apron, gloves. Procedure: 1. Obtain a cow eye and place it on your dissecting tray. 2. Examine the external surface of the eye. Note the thick cushion of adipose tissue that surrounds it. Find the optic nerve (cranial nerve II) as it leaves the eyeball, the severed remnants of the extrinsic eye muscles, the conjunctiva, the sclera, the iris, and the cornea. The cornea is normally transparent; if a preserved cow eye is used, it will appear opaque. 3. Trim away as much fat and connective tissue as you can. Holding the eye with the cornea facing upward, carefully make an incision with a point of your scissors into the sclera about onequarter of an inch above the cornea. The sclera is very tough, so you will have to apply a good deal of pressure to penetrate it. Take caution not to injure yourself as you make your incision, and be wary of fluid that may squirt out of the eye as you cut it. After making this incision, carefully cut around the circumference of of the eyeball, remaining parallel to the irisâ&#x20AC;&#x2122;s edge (see figure 1).

Figure 1: Make a cut with your scissors about one-quarter of an inch away from the edge of the iris.

4. Carefully lift the anterior part of the eyeball away from the posterior portion. The vitreous body, a clear, jellylike substance, should remain in the posterior part; if it does not, tease it away from the anterior part using a blunt probe. Note the following structures by examining the posterior portion: 43

a. Sclera: The “white of the eye” forms a tough protective wall for the delicate structures inside the eye. A mucous membrane called the conjunctiva lines the inner surface of the eyelids as well as the front of the sclera. b. Choroid coat: This tunic appears iridescent in the cow eye due to a special reflecting surface called the tapetum lucidum. This surface reflects the light within the eye and is found in the eyes of animals that live in low-intensity light conditions. It is not found in humans. The choroid is highly vascular. c. Retina: The neural layer of the retina appears as a delicate white membrane that resembles a wet tissue. It separates easily from the choroid coat. Notice its point of attachment, called the optic disc. 5. Return to the anterior portion of the eyeball to examine the following structures: a. Lens: This is a biconvex structure that is usually clear and malleable. In preserved specimens it feels hard to the touch and is opaque. b. Ciliary body: This black pigmented body encircles the lens. It is a muscle that contracts to adjust the thickness of the lens for focusing. c. Cornea: The cornea is a modified transparent portion of the sclera. This allows light to pass into the eye. d. Iris: This colored portion of the eye is actually a muscle. It functions to constrict or dilate the pupil, thus regulating how much light enters the eye. e. Pupil: Students often mistake the pupil for a “black dot” in the center of the eye, when in fact it is a hole in the center of the donut-shaped iris. The pupil allows light to enter the eye and reach the retina, which contains the sensory receptors for vision. 6. Make a drawing of the structures listed in bold.

Retina Tapetum lucidum

Ciliary body

Lens

Figure 2

Exercise 11: Visual Testing Purpose: After completing this exercise, you will understand how to test for visual acuity, astigmatism, and color blindness. You will also be able to locate your blind spot. Materials: Snellen visual acuity chart, astigmatism chart, index card, blind spot diagram, Ishihara plates Procedure: A: Visual Acuity 1. Stand facing the eye chart with your toes touching the 20-foot line. If you wear glasses, decide whether you want to test your vision with them on or off. 2. Cover you left eye with an index card. 3. Your partner should stand near the Snellen chart. Start with the top line of the chart and read the letters while your partner checks for accuracy. 4. If you read all letters on the assigned line correctly or miss one letter, go on to the next line. When your partner informs you that you have missed two or more letters, record the number on that line (example: 20/60, 20/200). 5. Repeat the procedure for the right eye. Record your vision below: Vision in left eye: ______________

Vision in right eye: ______________

Question 1: How do you translate your results from the visual acuity test? In other words, what does it mean if you have 20/40 vision in your right eye? ______________________________________________________________________________ ______________________________________________________________________________ Question 2: Why is it called â&#x20AC;&#x153;nearsightedâ&#x20AC;? if a person has a distance vision of 20/100? ______________________________________________________________________________ ______________________________________________________________________________ B: Astigmatism Note: The test for astigmatism should be performed without corrective lenses because astigmatic compensation is usually included in eyeglass prescriptions. 45

Procedure 1. Stand 8 to 10 feet from the astigmatism chart. The chart consists of a series of radial lines of equal thickness. 2. Cover your right eye with an index card and view the chart. If you have an astigmatism, some of the lines will appear exceptionally thick and dark. 3. Repeat the procedure for the right eye. 4. If you wear corrective lenses, repeat the procedure while wearing them to see if your prescription compensates for the astigmatism. Question 3: What is astigmatism? How does it affect vision? Can it be corrected? Research your answer. ______________________________________________________________________________ ______________________________________________________________________________ C: Demonstrating the blind spot Procedure: 1. Hold the blind spot figure (see about 20 inches from your face with the cross (â&#x153;&#x161;) directly in front of your right eye. 2. Close or cover your left eye and focus your right eye on the cross, which should be positioned so that it is directly in line with your right eye. 3. Keeping your left eye covered or closed, slowly bring the page closer to your face while focusing on the cross with your right eye. At a certain distance, the circle will disappear from your field of vision because its image falls on the blind spot of the eye.

Figure 1

Question 4: Why does this happen? Research what the blind spot is and explain why the circle disappears. ______________________________________________________________________________ ______________________________________________________________________________

D: Testing for Color Blindness Procedure: 1.View the Ishihara plates in bright light or sunlight while holding them 30 inches away and at a right angle to your line of vision. 2. Report to your lab partner what you see in each plate. Take no more than three seconds to make a decision. Your lab partner should write down your responses. 3. Have your partner check the accuracy of your responses using the answer key provided. Question 5: What types of color blindness are there? Research why it is more common in males than in females. _____________________________________________________________________________ _____________________________________________________________________________

Exercise 12: Pig Heart Dissection Purpose: After examining the anatomy of the pig heart, you will gain a better understanding of the chambers, hearts, and valves of the human heart and their respective functions. Materials: fresh pig heart, dissecting tray, dissection kit, apron, gloves, goggles Introduction: The dissection of a pig heart is valuable because it is similar in size and structure to the human heart. Use figures 1 and 2 at the end of this lab to guide your dissection. Procedure: 1. Rinse the pig heart in cold water. 2. Observe the texture of the pericardium. Find its point of attachment to the heart. Question 1: Where does the pericardium attach to the heart? ____________________________ _____________________________________________________________________________ 3. Examine the external surface of the heart. Notice the accumulation of adipose tissue, which in many cases marks the separation of the chambers and the location of the coronary arteries. Carefully scrape away some of the fat with a scalpel to expose the coronary blood vessels. 4. Slit open the parietal pericardium and cut it from its attachment points to the heart. Observe the visceral pericardium, or epicardium. 5. Identify the base and apex of the heart, and then identify the two wrinkled auricles, ear-like flaps of tissue projecting form the atrial chambers. The balance of the heart muscle is ventricular tissue. To identify the left ventricle, compress the ventricular chambers on each side of the longitudinal fissures carrying the coronary blood vessels. The side that feels thicker and more solid is the left ventricle. The right ventricle is much thinner and feels somewhat flabby when compressed. Question 2: Why is the left ventricle much thicker than the right ventricle? _________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 49

6. Cut through the wall of the aorta until you see the aortic semilunar valve. Identify the two openings into the coronary arteries just above the valve. Insert a blunt probe into one of these holes to see if you can follow the course of a coronary artery across the heart. 7. Turn the heart to view its posterior surface. Try to identify the thin-walled pulmonary veins entering the left atrium. Identify the superior and inferior venae cavae entering the right atrium. Compare the approximate diameter of the superior vena cava with that of the aorta. Question 3: Which has a larger diameter: the superior vena cava or the aorta? _______________ ______________________________________________________________________________ Question 4: Which has thicker walls? _______________________________________________ Question 5: Why do you suppose these differences exist? _______________________________ ______________________________________________________________________________ ______________________________________________________________________________ 8. Insert a blunt probe into the superior vena cava and use scissors to cut through its walls so that you can see the interior of the right atrium. Do not extend your cut entirely through the atrium or into the ventricle. Observe the tricuspid valve. Question 6: How many flaps does the tricuspid valve have? _____________________________ 9. Pour some water into the right atrium and allow it to flow into the ventricle. Slowly and gently squeeze the right ventricle to watch the closing action of this valve. (If you squeeze too vigorously, you’ll get a face full of water.) Drain the water from the heart before continuing. 10. Return to the pulmonary trunk and cut through its anterior wall until you see the pulmonary valve. Pour some water into the base of the pulmonary trunk to observe the closing action of this valve. 11. Drain the heart again. Return to the superior vena cava, and continue the cut made in its wall through the right atrium and tricuspid valve into the right ventricle. 12. Next, make a longitudinal incision through the aorta and continue it into the left ventricle. Notice how much thicker the myocardium (muscle) of the left ventricle is than that of the right ventricle. Question 7: Are the chordae tendinae (“heart strings”) observed in the right ventricle also present in the left ventricle? _____________________ 13. Count the number of cusps in the mitral valve. How many do you see? __________________ 14. Continue your incision from the left ventricle superiorly into the left atrium. Try to locate the entry points of the pulmonary veins into the left atrium.

15. Observe the endocardium inside the left ventricle. Question 8: Why do you think this tissue is so smooth? ________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 16. Return the heart to your plastic bag and place it in the designated container. Return all equipment and wash your hands thoroughly with soap and water.

Superior vena cava Aorta

Aorta

Pulmonary veins Pulmonary trunk Right atrium Right atrium

Left atrium Left atrium Right ventricle

Left coronary artery Left ventricle Right ventricle Left ventricle

Right coronary artery

Figure 1: Anterior view of pig heart

Figure 2: Posterior view of pig heart

Exercise 13: Pulse and Heart Sounds Purpose: During this activity, you will learn how to detect heart sounds. Materials: stethoscope, alcohol wipe Introduction: The term pulse refers to the alternating surges of pressure (expansion and then recoil) in an artery that occur with each beat of the left ventricle. Normally the pulse rate equals the heart rate, and the pulse averages 70 to 76 beats per minute in the resting state. Conditions of the pulse other than its rate are also useful. Can you feel it stronglyâ&#x20AC;&#x201D;does the blood vessel expand and then recoil (sometimes visibly) with the pressure wavesâ&#x20AC;&#x201D;or is it difficult to detect? Is it like the regular ticking of a clock, or does it seem to skip beats? As we learned in our study of the heart, two distinct heart sounds can be heard during each cardiac cycle. These heart sounds are commonly described by the monosyllables lub and dup. The sequence is lub-dup, pause, lub-dup, pause, and so on. The first sound (lub) occurs as the atrioventricular valves close during the beginning of systole. The second heart sound (dup) occurs as the semilunar valves close at the end of systole. The closing of these valves causes the heart sounds heard by auscultation, which means listening to body sounds, typically by using a stethoscope.

Part 1: Pulse Procedure: 1. The pulse may be felt easily on any artery close to the body surface when the artery is compressed over a bone or firm tissue. Palpate (examine by touch) the following pulse or pressure points on your partner by placing the tips of your index and middle fingers of one hand over the artery (do not use your thumb). It helps to compress the artery firmly as you begin your palpation and then immediately ease up on the pressure slightly. In each case, notice the regularity of the pulse, and rate its force. Figure 1 shows superficial pulse points to be palpated. 2. Work with your partner to practice palpating pulse at the following pulse points. Place a check next to each one you successfully detect. _____ Common carotid artery: at the side of the neck _____ Temporal artery: anterior to the ear, in the temple region _____ Radial artery: at the lateral aspect of the wrist, just above the thumb 53

_____ Brachial artery: in the antecubital (hmm, what area is this again?) region, at the point where it splits into the radial and ulnar arteries _____ Popliteal artery: at the back of the knee _____ Posterior tibial artery: just above the medial malleolus (the inner bump of your ankle) _____ Dorsalis pedis artery: on the dorsum (top) of the foot

Figure 1: Common pulse points (Pearson Education)

Question 1: Which pulse had the greatest amplitude (strength)? ________________________ Question 2: Which pulse had the least amplitude? _________________________ Question 3: Can you offer any explanation for this difference? _________________________ ____________________________________________________________________________ ____________________________________________________________________________ 3. Because of its easy accessibility, the radial pulse is often taken during exams. With your partner sitting quietly, practice counting the radial pulse for 1 minute. (If you have difficult detecting a pulse at this location, try palpating the carotid artery in the neck). Make three counts and average the results. Count 1: __________ Count 2: __________ Count 3: __________ Average: __________

Question 4: Define pulse. ________________________________________________________ ______________________________________________________________________________ Question 5: In which pulse point was it easiest for you to find a pulse? Which point was the hardest? ______________________________________________________________________ _____________________________________________________________________________

Part 2: Heart Sounds Procedure: 1. On your own body, find the location to auscultate the mitral valve (the fifth intercostal space just left of the left nipple) and the aortic valve (second intercostal space just right of the sternum. Mr. Clancy will place stickers on the articulated skeleton to show where you will auscultate these heart sounds. You can also refer to figure 1.

Figure 1

2. Obtain a stethoscope and alcohol wipe. Clean the earpieces with the wipe and let them air dry. Note: Earpieces should be angled forward when placed in the external ear canal to facilitate hearing the heart sounds. 3. In order to clearly hear the first heart sound (lub), you will auscultate the mitral valve. You may listen to your own heart or your partnerâ&#x20AC;&#x2122;s. 4. Place the diaphragm at the apex of the heart, located at the fifth intercostal space just left of the nipple. If the heart sound is difficult to hear, have your subject lean forward to tip the heart against the anterior thoracic wall and try again.

5. To auscultate the aortic valve, palpate the suprasternal (jugular) notch and then the sternal angle (marks the insertion of the second rib). Mr. Clancy will indicate this spot on the articulated skeleton. Now drop down one inch on the sternum from the sternal angle and then move right another inch. You should now be at the second intercostal space just to the right of the sternum where you can clearly hear the dup, or second heart sound. Question 6: At rest, which sound is louder: the lub or dup? ____________________________

Exercise 14: Blood Pressure Purpose: During this activity, you will learn how to measure blood pressure. Materials: sphygmomanometer, stethoscope, alcohol wipe Introduction: Blood pressure is the pressure the blood exerts against the inner blood vessel walls; it is generally measured in the arteries. Because the heart alternately contracts and relaxes, the rhythmic flow of blood into the arteries causes the blood pressure to rise and fall during each beat. Thus, you must take two blood pressure readings: the systolic pressure, which is the pressure in the arteries at the peak of ventricular ejection, and the diastolic pressure, the pressure during ventricular relaxation. Blood pressures are reported in millimeters of mercury (mm Hg), with the systolic pressure appearing first; for example, 120/80 translates to a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg. Normal blood pressure varies considerably from one person to another. The sphygmomanometer, commonly called a blood pressure cuff, is an instrument used to measure blood pressure. It consists of an inflatable cuff with an attached pressure gauge. The cuff is wrapped snugly around the arm and inflated to stop flow of blood to the forearm. As the cuff pressure is gradually released, the examiner listens with a stethoscope over the brachial artery for characteristic sounds called the sounds of Korotkoff, which indicate the resumption of blood to the forearm. The pressure at which the first soft tapping sounds are heard is recorded as the systolic pressure. As the pressure is reduced further, blood flow becomes more turbulent, and the sounds become louder. Below the diastolic pressure, when an artery is no longer compressed, blood flows freely and the sounds of Korotkoff can no longer be heard. The pressure at which the sounds disappear is recorded as the diastolic pressure. Procedure: 1. Work in pairs to obtain radial artery blood pressure readings. Obtain a stethoscope, alcohol swabs, and a sphygmomanometer. Clean the earpieces of the stethoscope with the swabs, and check the cuff for the presence of trapped air by compressing it against the laboratory table. (A partially inflated cuff will produce erroneous measurements.) 2. Have your partner sit in a comfortable position with one arm resting on the lab table (approximately at heart level if possible). Wrap the cuff around your her arm, just above the elbow, with the inflatable area on the medial arm surface. The cuff may be marked with an arrow; if so, the arrow should be positioned over the brachial artery. Secure the cuff by tucking the distal end under the wrapped portion or by bringing the Velcro速 areas together. (See figure 1) 57

Figure 1: Morgan Bryant ’14 prepares to have her blood pressure measured by Caroline O’Neill ’14.

3. Palpate the brachial pulse and place the diaphragm of the stethoscope over this pulse point. Note: The cuff should not be kept inflated for more than one minute. If you have any trouble obtaining a reading within this time, deflate the cuff, wait two minutes, and try again. A prolonged interruption of blood flow can cause fainting. 4. Inflate the cuff to approximately 160 mm Hg, and slowly release the pressure valve. Watch the pressure gauge as you listen for the first soft thudding sounds of the blood spurting through the partially blocked artery. Make a mental note of this pressure (systolic pressure), and continue to release the cuff pressure. You will notice first an increase, then a muffling, of the sound. Record, as the diastolic pressure, the pressure at which the sound disappears. Record your results. Patient: __________________________________ Systolic pressure: ________________

Diastolic pressure: _______________

Question 1: Define blood pressure, systolic pressure, and diastolic pressure. ________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Question 2: What vital role does blood pressure play? _________________________________ _____________________________________________________________________________ Question 3: What do you think would be the effect of hemorrhage (bleeding) on a person’s blood pressure? ______________________________________________________________________________ ______________________________________________________________________________ 58

Exercise 15: External Anatomy of the Fetal Pig Purpose: In this exercise you will examine the external anatomy of the fetal (unborn) pig. Materials: fetal pig, dissecting kit, dissecting tray, string, plastic bag, gloves, apron, goggles Introduction: The fetal pig exhibits the basic structural and functional organization that is found in many mammals, including humans. Thus, when you study the pig, you are in essence studying yourself. Students often ask about the source of these specimens. They were purchased from a biological supply company that prepared them after they had been purchased from a facility where sows (female pigs) are processed for food. The gestation period (time of development in the femaleâ&#x20AC;&#x2122;s uterus) for a pig is about 112-115 days. Your specimen is approximately 100 days of age. After being removed from the sow, the fetus was treated with a preservative, and latex or a similar compound was injected into the major blood vessels. Thus, the arteries will appear red in color and the veins will be seen as blue. As you proceed with the dissection, remember that your goal is to first identify the various organ systems and their component parts and then develop an understanding of the relationships among these systems. From your study of this organism you will be able to make comparisons to the human body. Procedure: 1. The body sections of the fetal pig are the head, neck, limbs, tail, and trunk. The trunk is divided into two regions: the upper area called the thorax (chest) and the lower area called the abdomen. 2. The eyes are probably closed. If they are, carefully open them with a probe and find the nictitating membrane. This moves across the eyeball and helps keep it clean. You have a vestige of such a membrane in the medial corner of each eye. Question 1: In humans, the third eyelid (nictitating membrane) and the appendix are vestigial organs. What does this mean? ______________________________________________________________________________ ______________________________________________________________________________ 59

3. The external ears or pinnae are laid back against the head. Each surrounds an opening leading to the eardrum. 4. The snout is composed of bone, cartilage, and other tough connective tissue. Its strength and shape make it well adapted for pushing through soil in search of food. The openings are called the nares. 5. Place your pig on its back (the dorsal surface) in the dissecting tray. Note that the umbilical cord emerges from the ventral surface of the abdomen. Previously, it had been connected to the placenta, which attached the fetus to the wall of the femaleâ&#x20AC;&#x2122;s uterus. See figure 1. 6. Locate the teats (nipples) leading to the mammary glands. You will see five to eight pairs on the thoracic and abdominal surfaces. Question 2: Can teats be used to determine the sex of your pig? Why or why not? ___________ _____________________________________________________________________________ Question 3: Why would the number of teats on a female pig be important after she had given birth to a large litter of piglets? _____________________________________________________________________________ _____________________________________________________________________________ 7. Lift the tail to find the anus. This is the opening through which undigested materials are eliminated. 8. Examine the feet and limbs. Each toe has a pad of a white horny substance that later hardens into a hoof. Pigs walk on the tips of these toes. Question 4: How does this differ from the part of your foot that bears your weight when walking? _____________________________________________________________________________ _____________________________________________________________________________ 9. Determine the sex of your pig. A male is identified by the scrotal sacs located ventral to the anus and between the upper ends of the hind limbs. The testes may or may not be present in the scrotal sacs depending on whether they have descended from within the abdominal cavity. If you have a male, also locate the urogenital opening of the penis just posterior to the base of the umbilical cord. 10. If your specimen is a female, the urogenital opening can be located immediately ventral to the anus. A small, pointed genital papilla marks its location.

Question 5: Imagine a surgeon inking a straight line on the surface of your abdomen from your right hip to your navel. The surgeon then marks a spot exactly halfway along this line. This location is called McBurneyâ&#x20AC;&#x2122;s Point. Why do you think this precise area is significant? ____________________________________________________________________________ _____________________________________________________________________________

Umbilical cord

Teats

Anus

Figure 1: Ventral view of the fetal pig.

Exercise 16: The Digestive System of the Fetal Pig Purpose: During this exercise you will explore the major organs of the fetal pig’s digestive system. Materials: fetal pig, dissecting kit, dissecting tray, string, plastic bag, gloves, apron, goggles Procedure: 1. Place your specimen ventral side up on the dissecting tray. Tie one end of a piece of string to the ankle of one of the forelimbs. Pass the string beneath the tray and tie it to the other ankle. Make the string as taut as possible. Do the same with the hind legs. (When you finish your work for this lab, do not untie the strings from the legs. Rather, slip the strings from under the tray, leaving them attached to the pig for the next lab.) 2. Refer to figure 1. Use your scissors to cut through the wall of the abdomen to make a partial circle (1) around the umbilical cord. Be careful not to cut too deeply; doing so might damage the underlying organs. 3. Make incisions 2 and 3, extending each cut laterally. 4. Make cuts 4, 5, and 6. By doing so, you will form two flaps in the body wall and expose the organs of the abdominal cavity. 5. In order to obtain an unobstructed view of the organs, you must first locate and free the umbilical vein. This blood vessel runs from the base of the umbilical cord to the liver. Cut it at its midpoint in such a way that visible stumps remain at both ends. 6. The organs that are part of the digestive tract are structured to perform one or more of the following functions: • • • • •

Moving ingested materials through the digestive tract. The physical breakdown (mechanical digestion) of food into smaller pieces. Secreting enzymes to accomplish chemical digestion of foods into simpler organic molecules. Absorbing the end products of digestion into the bloodstream. Eliminating materials that were not digested (for example, fiber).

7. Locate the peritoneum. It is a membrane that lines the inner walls of the entire abdominal cavity. It is shiny in appearance and slippery to the touch. A similar membrane, the mesentery, surrounds and suspends the digestive organs. 63

4 1

Figure 1: Ventral view of the fetal pig showing the necessary incisions.

Question 1: Why would an infection in one area of the peritoneum become widespread and life threatening? (This is why a ruptured appendix was once a major cause of death in young children.) _____________________________________________________________________________ _____________________________________________________________________________ Question 2: Why is it an advantage for the digestive organs to be surrounded by and enclosed in a slippery membrane? _____________________________________________________________________________ _____________________________________________________________________________ 8. The liver is the largest organ in the abdominal cavity. It is reddish brown in color and is located at the anterior end of the cavity, immediately posterior to the diaphragm. Note how it fits into the arch of the diaphragm. The liver has many functions, but its main digestive function is to produce bile. This liquid acts in the small intestine to emulsify large lipid globules into smaller lipid droplets. Question 3: Is the emulsification of lipids by bile an example of mechanical or chemical digestion? Why? (Look up the word emulsion.) _____________________________________________________________________________ _____________________________________________________________________________ 9. Lift the central lobe of the liver to find the gall bladder. This is a greenish sac attached to the underside of the liver at the point where the umbilical vein enters the liver. 10. The gall bladder stores bile produced by the liver. When bile is released from the gall bladder following the ingestion of lipid-rich foods, it travels through ducts to the first part of the small intestine, the duodenum. Carefully tease away some of the liver tissue to locate these ducts. Question 4: Why would a â&#x20AC;&#x153;stoneâ&#x20AC;? lodged in the bile duct be a problem for an individual? _____________________________________________________________________________ _____________________________________________________________________________ 11. The stomach is an enlarged portion of the digestive tract located on the left side of the body, partially covered by the liver. At its anterior end, it connects to the esophagus. Posteriorly, it connects to the duodenum of the small intestine. In addition to the physical churning of food made possible by the muscular walls of the stomach, the chemical digestion of proteins begins here.

Diaphragm

Liver

Spleen

Small intestine

Large intestine

Umbilical artery

Figure 2: Digestive system of the fetal pig. In this photograph, the stomach is covered by the liver.

12. The spleen is a long, flattened, dark red organ attached by the mesentery to the outer curvature of the stomach. The spleen has no digestive function; it produces red blood cells in the fetus and then stores them in the adult.

13. Locate the pancreas. (This may be difficult to do.) It is an elongated granular organ that lies along the dorsal surface of the abdominal cavity between the stomach and duodenum. One end is in contact with the duodenum while the other end extends toward the spleen. Lift the stomach to search for it. It looks somewhat like a small clump of oatmeal. The pancreas produces both hormones and several digestive enzymes that are secreted into the duodenum. 14. The small intestine is divided into three sections. The first part, the duodenum, is about one inch long in the fetal pig and runs along the edge of the pancreas. The other sections, the jejunum and ileum, are about equal in length, but there are no clear borders recognizable between them. Note that the coils of the small intestine are held together by the mesentery. The considerable length of the small intestine is related to its function because: a. Most chemical digestion of food takes place here. b. Digestion is completed here. c. The absorption of the end products of digestion into the bloodstream takes place here. Question 5: In the small intestine, the end products of the chemical digestion of carbohydrates are monosaccharide molecules. What are the products of protein digestion? _____________________________________________________________________________ _____________________________________________________________________________ 15. Mr. Clancy will prepare a section of ileum for you to view under a microscope. Examine the inner lining. Its velvety appearance is due to the presence of villi, numerous tiny, fingerlike projections extending from the small intestineâ&#x20AC;&#x2122;s walls. Villi greatly increase the surface area of the small intestineâ&#x20AC;&#x2122;s inner walls. Most of the end products of digestion are absorbed through them. 16. Follow the length of the small intestine until you find the place where it joins the large intestine, or colon, in the lower right side of the abdominal cavity. At this junction, look for a short pouch called the cecum. In humans, a small blind tube called the vermiform (wormlike) appendix is attached to the cecum. 17. The rectum lies against the dorsal body wall at the end of large intestine. It is a short, straight tube that opens to the outside via the anus. Do not trace the rectum to the anus at this time. Separate some of the coils of the large intestine and note the many blood vessels in the mesentery. 18. Since digestion is completed in the small intestine, the large intestine has no digestive function. Rather, its job is to reabsorb water from the undigested materials that pass through it, causing the matter to become solid and form feces prior to their elimination from the body through the anus. Failure of this process, in infants in particular, can lead to life-threatening dehydration. 67

Pancreas

Stomach

Figure 3: A view of the digestive system with the liver cut away to reveal the stomach.

Exercise 17: The Cardiovascular and Respiratory Systems of the Fetal Pig Purpose: During this activity you will: • • • • •

Identify the major cardiovascular and respiratory structures of the fetal pig. Relate these structures to their functions. Differentiate between the two main types of blood vessels and the two types of heart chambers. Outline the differences between the circulatory patterns of a fetal pig and an adult pig. Locate the thymus and thyroid glands.

Materials: fetal pig, dissecting kit, dissecting tray, string, plastic bag, label, gloves, apron, and goggles Procedure: 1. Remove your pig from the plastic bag and rinse it in the sink. Place the pig on its dorsal surface in the dissecting tray and secure it by passing the strings beneath the tray. 2. Use scissors to extend your original midline incision from the diaphragm anteriorly into the neck (see figure 1). To accomplish this, you will have to cut through the hard sternum, which along with the ribs forms a protective shield over the heart. 3. Make two additional cuts laterally where the neck joins the trunk. Avoid cutting too deeply and damaging underlying structures. Examine the organs and vessels of the thoracic cavity. Refer to figure 2. 4. The lungs fill most of the space within the thoracic cavity. They partly cover the heart and extend down to and fit onto the curve of the diaphragm. Each lung is divided into sections or lobes. Observe how the ribs form a cage enclosing the thoracic cavity. Pleural membranes line the inner surface of the thoracic cavity and the outer surface of the lungs. 5. Place your fingers on the bottom of your own rib cage. This is how far down your lungs extend. 6. Locate the thymus gland. It is a soft, whitish structure with clumped material that lies over the anterior portion of the heart and extends to the neck. The thymus plays a vital role in the development of the body’s immune defenses. 69

Figure 1: Incision lines for opening the thoracic cavity.

Larynx

Trachea

Thymus gland

Apex of heart Lobe of right lung

Lobe of left lung

Diaphragm Figure 2: The thoracic cavity of the fetal pig.

7. Remove the thymus gland and inspect the heart. Note how the pointed end of the heart (the apex) rests against the anterior surface of the diaphragm. The heart is surrounded by a sac-like membrane called the pericardium. 8. On both sides of the pericardium, locate the phrenic nerves. They are delicate and resemble long pieces of fine, whitish sewing thread. Free them and trace anteriorly into the neck and posteriorly into the diaphragm. These nerves help to control the rate at which the heart beats. 9. Remove the pericardium to study the heart more closely. 10. The heart is composed mostly of muscular tissue formed into four chambers: a. The left and right atria (singular: atrium) are thin-walled chambers forming the anterior end of the heart. They resemble two small, bent ears perched on top of the heart. The atria are the receiving chambers; they collect blood being returned to the heart. b. The left and right ventricles are the most muscular chambers. They make up the bulk of the heart. Both ventricles are pumping chambers. Together they send blood to all parts of the body. 11. The coronary arteries can be found in a groove that crosses the ventral surface of the heart. These blood vessels supply blood to the heart muscle itself. 12. Examine the organs of the neck region (see figure 3). Locate the trachea (windpipe). The trachea is the tube through which air is carried to the lungs. You can recognize it the series of rings made of cartilage arranged one above the other along its length. These rings keep the trachea open at all times. The trachea divides into two tubes, the bronchi, that extend into the lungs. 13. The esophagus lies dorsal to the trachea. Food is transported through this tube to the stomach. Its walls are softer than those of the trachea and it is generally collapsed and closed when no food is passing through it. Use your probe to free it from the membranes attaching it to the trachea. 14. Identify the larynx. It is a whitish, enlarged structure at the anterior end of the trachea. Use your probe to clear away the surrounding membranes and muscles. Tap the larynx with your probe to see how hard it is. The larynx is called the â&#x20AC;&#x153;voice boxâ&#x20AC;? because it contains the vocal cords. 15. Find the thyroid gland lying on the ventral surface of the trachea near its base. It is round and reddish brown in color. This gland secretes a hormone that controls the bodyâ&#x20AC;&#x2122;s rate of metabolism.

16. Lateral to the trachea and running parallel on both sides of it are the vagus nerves. Along with the phrenic nerves that you identified earlier, they also help control the rate at which the heart beats.

Larynx

Left common carotid artery

Trachea

Figure 3: The neck region of the fetal pig.

17. Lift the heart at its apex and tilt it backward so that its dorsal surface can be seen. Observe two large veins entering the right atrium. The superior vena cava returns blood low in oxygen to the heart from the head, neck, and forelimbs. The inferior vena cava returns blood low in oxygen to the heart from the lower parts of the body. 18. The paired external and internal jugular veins return blood to the heart from the head and neck. The internal jugular veins are located medially, close to the trachea. The external jugular veins are located more laterally. The subclavian veins drain blood from most of the shoulders and the front limbs. Locate the point at which all of these vessels merge to form the superior vena cava. 19. Turn your attention again to the heart and locate the pulmonary trunk. This is a large, short blood vessel that arises from the anterior end of the right ventricle, curves between the atria, and then divides into the left and right pulmonary arteries, which carry blood to the lungs to be oxygenated. The pulmonary trunk is the most conspicuous of the large blood vessels entering and leaving the heart. Using it as a landmark, you will have little difficulty locating and identifying the other major blood vessels.

20. The aorta is a large artery that emerges from the left ventricle and passes dorsal to the pulmonary trunk. The two small coronary arteries branch off of the aorta as it exits the heart. The aorta then branches to the left side of the body and travels posteriorly along the mid-dorsal line. 21. As the aorta arches to the left, it gives off branches that become the right and left subclavian arteries in the shoulders. Further branching results in the formation of the right and left common carotid arteries, which supply blood to the head and neck. 22. Use your probe to move the digestive organs out of the way to reach the arteries found along the dorsal surface of the body wall. With your probe, peel away the peritoneal membrane that forms the dorsal surface of the body wall. 23. Locate the aorta. See if you can identify its branches listed below: a. celiac artery: an unpaired artery that arises from the aorta just posterior to the diaphragm. It supplies blood to the stomach, spleen, and liver. b. superior mesenteric artery: also unpaired, this blood vessel arises just posterior to the celiac artery and supplies nutrient-rich blood to the small and large intestines. c. renal arteries: paired arteries that supply blood to the kidneys. d. genital arteries: paired arteries that supply blood to the ovaries in females and the testes in males. e. posterior mesenteric artery: an unpaired artery that leaves the dorsal aorta slightly posterior to the genitals. It supplies blood to the posterior colon and rectum. f. external and internal iliac arteries: arise at the posterior end of the aorta. The external iliac arteries supply blood to the hind limbs. The internal iliac arteries lead to the umbilical arteries. Question 1: Cholesterol is a lipid material that thickens the walls of arteries, reducing the blood flow through them. Why is this process of particular concern when it occurs in the coronary arteries or carotid arteries? _____________________________________________________________________________ _____________________________________________________________________________ Question 2: When a patient is suffering from pleurisy, where is the infection? _____________________________________________________________________________ _____________________________________________________________________________

Question 3: Most arteries carry oxygenated blood. Why are the pulmonary arteries the exception to this rule? _____________________________________________________________________________ _____________________________________________________________________________ Question 4: What is meant by the expression, “The drink went down the wrong tube”? _____________________________________________________________________________ _____________________________________________________________________________ 25. It is time for you to become a surgeon. Using your dissection tools, carefully remove the heart, lungs, trachea, and larynx intact, as shown below.

Figure 4: The heart, lungs, larynx, and trachea removed from the fetal pig.

Exercise 18: The Digestive System of the Shark: Part 1 Purpose: During this lab you will examine the digestive system of the dogfish. Materials: dogfish, dissecting kit, large dissecting tray, safety goggles, apron, gloves Procedure: 1. Place your shark on the dissection tray ventral side up. 2. Using scissors, make an incision immediately cranial to the cloaca. Cut through the skin and muscle cranially and slightly to the left of the median line until your reach the pectoral girdle (see cut #1 in figure 1). It is important to avoid cutting along the midline near the pectoral girdle so that you will not damage the underlying structures. Carefully extend the incision above the pelvic girdle the the level of the second gill slit. 4. Make two sets lateral incisions through the body wall in the pectoral girdle and the pelvic girdle (cuts #2 and #3 in figure 1). Note the body layers that have been cut; from the surface passing deep, they are the skin, a thin layer of connective tissue, the muscle layer, and the smooth membrane that lines the pleuroperitoneal cavity, called the parietal peritoneum. 5. You have now exposed the large body cavity known as the pleuroperitoneal cavity. Now pull back the flaps of the ventral body wall to observe the internal anatomy of your shark. 6. Using figure 2 to help you in your search, identify the following structures: a. Liver: a large, grayish organ consisting of long right and left lateral lobes and a short median lobe. b. Falciform ligament: a sickle-shaped membrane connecting the liver to the inside ventral body wall. c. Esophagus: a constriction between the pharynx and stomach. Unlike the esophagus of higher vertebrates, the sharkâ&#x20AC;&#x2122;s esophagus is short and wide. d. Stomach: a large, J-shaped organ that fills much of the cavity. e. Spleen: a dark-colored organ near the caudal end of the stomach. It is part of the lymphatic system. f. Intestine: a caudal continuation of the stomach. Continuing caudally, it consists of three sections: the duodenum, the valvular intestine, and the colon. g. Pancreas: a flattened white gland on the cranial portion of the duodenum. It secretes essential digestive enzymes and insulin. 75

h. Gall bladder: a small greenish sac on the median cystic lobe of the liver. It stores bile produced by the liver. i.

Kidneys: paired brown structures lying between the dorsal body wall and the parietal peritoneum on either side of the vertebral column.

7. Close the walls of the shark and secure it with your name tag. Question 1: Our esophagus is long and narrow, while a sharkâ&#x20AC;&#x2122;s is short and wide. Why do you think this is so? (Hint: How do we handle food in our mouths differently from a shark?) _____________________________________________________________________________ _____________________________________________________________________________

Cut #2

Cut #1

Cut #3

Figure 1: Incisions through the ventral surface of the shark.

Median cystic lobe of liver Cranial portion of stomach Lateral lobe of liver Lateral lobe of liver

Fundic portion of stomach

Pancreas

Pyloric portion of stomach

Spleen

Spiral intestine

Figure 2: Organs of the pleuroperitoneal cavity.

Exercise 19: The Digestive System of the Shark: Part 2 Purpose: During this lab, you will continue your examination of the digestive system of the dogfish. Materials: dogfish, dissecting kit, large dissecting tray, safety goggles, apron, gloves Procedure: 1. Place your shark on the tray, ventral side up. Open the pleuroperitoneal cavity. 2. Examine the stomach. It is divided into three regions. The upper part is called the cranial portion. Question 1: Why do you think this section is called the cranial portion? ____________________ ______________________________________________________________________________ 3. The lower-middle part is referred to as the fundic stomach. Fundus means the bottom or base of an organ. The stomach ends at the pyloric sphincter. Here you should feel a thick involuntary muscle. Pylorus means “gatekeeper.” Question 2: What do you think the function of the pyloric sphincter is? ____________________ ______________________________________________________________________________ 4. Slit open the stomach along its longitudinal axis and remove any food present. Question 3: If there is food in the stomach, can you determine whether or not it was ingested recently? Explain. _____________________________________________________________________________ _____________________________________________________________________________ 5. The stomach wall is composed chiefly of muscle. Inspect the rugae (folds) on its inner lining. Question 4: Why do you think rugae are present? _____________________________________  _____________________________________________________________________________ _____________________________________________________________________________

6. On a sheet of white paper, make a sketch of your shark, drawing it ventral side up. Be sure to include and label all parts that appear in bold print. In addition, label the following parts from the previous lab: a. pleuroperitoneal cavity b. liver, including the two lateral lobes and the median cystic lobe c. falciform ligament d. esophagus e. spleen f. spiral intestine g. pancreas h. gall bladder

Gall bladder Esophagus Liver Stomach Ventral pancreas

Spleen Spiral intestine Cloaca

Figure 1: Ventral view of the sharkâ&#x20AC;&#x2122;s viscera.

Exercise 20: The Digestive System of the Shark: Part 3 Purpose: To remove the digestive tract of the dogfish. Materials: dogfish, dissecting kit, large dissecting tray, safety goggles, apron, gloves Procedure: 1. Place your specimen on the tray ventral side up. 2. Use scissors to cut through the cranial portion of the esophagus. 3. Use your thumb and index finger to locate the end of the digestive tube, the colon. The colon communicates with the cloaca. Cut through the colon as close to the cloaca as possible. 4. Using your fingers and a blunt probe, tease away any blood vessels and membranes that connect the digestive tract to the body cavity. Carefully remove the entire digestive tract and arrange it on your dissecting tray. 5. Place the rest of your shark in the designated trash container. 6. Take turns with your partner identifying the following parts of the digestive tract: esophagus, stomach, duodenum, valvular intestine, and colon. 7. Use a scalpel to open the valvular intestine. Make a shallow incision along one side between the large blood vessels that travel lengthwise to its wall. Note its structure. The spiral valve located within serves to increase the surface area for the absorption of nutrients. Question 1: Humans do not have spiral valves to increase the surface area of the small intestine. How is this accomplished in the human small intestine? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Â 8. Make a sketch of the digestive tract of your shark, labeling each of the bold-faced structures above. Draw it as you see it, with the esophagus, stomach, and valvular intestine slit open. 9. Complete the chart on the next page. Be sure to include as many comparisons as you can. 10. When you have finished, place the digestive tract of your shark in the designated trash container. 81

Comparison of Shark and Human Digestive Systems

Organ

Shark

Human

Oral cavity

Teeth

Nostrils

Pharynx

Esophagus

Stomach

Small Intestine

Large Intestine

Cloaca/Anus

Liver

Exercise 21: Tactile Sensitivity Purpose: During this activity, you will indirectly measure cutaneous touch receptor density. Materials: toothpicks, millimeter ruler Introduction: Some areas of the skin have greater tactile (touch) sensitivity than others. The greater the number of cutaneous receptors in the area (touch receptor density), the greater the tactile sensitivity of that area. In addition, the size of the somatosensory cortex area in the brain receiving information from a specific body area is directly proportional to the cutaneous receptor density. The two-point discrimination test is an indirect measure of cutaneous touch receptor density. A subject is touched by two closely spaced points and asked if she can feel both points. The objects are moved farther apart until two points can be felt. An area of skin with a greater density of touch receptors is more sensitive to touch and can discriminate between two points closer together than an area with a lower density of touch receptors. Procedure: 1. Begin by making a prediction. List the cutaneous receptor density of the following areas in order from greatest to least: cheek, fingertip, palm, forearm, back of leg. a. ________________________________ b. ________________________________ c. ________________________________ d. ________________________________ e. ________________________________ 2. Have your partner close her eyes. For each area listed on the chart on page 84, place the toothpick points on the skin. 3. Put the points of the two toothpicks together. Touch the pair of toothpicks to your partnerâ&#x20AC;&#x2122;s skin. Ask her if one or two points can be felt. 83

4. Increase the distance between the toothpick points. For the fingertip and palm, increase the distance 1 millimeter. For the cheek, forearm, and back of leg, increase the distance by 2 millimeters. 5. Continue to increase the distance between the toothpick points until your partner can feel two points. This distance is the two-point discrimination distance and is measured in millimeters. Record this value in the chart. 6. Repeat for each area of the body and record your results. 7. Switch. Have your partner test you. 8. Calculate the reciprocal (1/two-point distance) of the two-point discrimination distance for each area and record the value in the chart. The reciprocal represents the portion of the somatosensory cortex that receives information from sensory receptors for a given body area. Areas with high sensory receptor density are represented by a correspondingly greater area of cerebral cortex. 9. Collect the individual two-point discrimination distance and reciprocal values for each body area from all lab groups. 10. Calculate the average two-point discrimination distance and reciprocal for each body area and record them in your chart.

Area Tested

Two-Point Discrimination Distance (mm)

Reciprocal (mm)

Cheek Fingertip Palm Forearm Back of leg

Class TwoPoint Discrimination Distance (mm)

Class Average Reciprocal (mm)

Question 1: Which body area had the highest average of cutaneous receptor density? Which had the lowest? ______________________________________________________________________________ ______________________________________________________________________________ Question 2: Was there any variation in tactile sensitivity per body area among your classmates? If so, describe your results. ______________________________________________________________________________ ______________________________________________________________________________ Question 3: Which body area tested was represented by the largest area of cerebral cortex? Why do you think this was the case? ______________________________________________________________________________ ______________________________________________________________________________ Question 4: Discuss why cutaneous receptor density varied or did not vary among individuals. ______________________________________________________________________________ ______________________________________________________________________________

References Allen, Connie, and Harper, Valerie. Laboratory Manual for Anatomy and Physiology, fourth edition. New Jersey: John Wiley and Sons, 2011. Ashley, Laurence, and Chaisson, Robert. Laboratory Anatomy of the Shark. Dubuque: William C. Brown Publishers, 1988. Bohensky, Fred. Photo Manual and Dissection Guide of the Fetal Pig. Wayne, New Jersey: Avery Publishing Group, Inc., 1978. Hammond, Robert. Human Vision. Burlington, North Carolina: Carolina Biological Supply Company, 1980. Koepfer, Helen, and Abramson, Donald. Life in the Lab: A Manual for Non-Majors, fourth edition. Dubuque, Iowa: Kendall/Hunt Publishing Company, 1999. Marieb, Elaine. Essentials of Human Anatomy and Physiology Laboratory Manual, second edition. San Francisco: Benjamin Cummings, 2003. Phillips, Roger. Dissection of the Fetal Pig. Burlington, North Carolina: REX Educational Resources Company, 1985. Wingerd, Bruce. Dogfish Anatomy and Dissection Guide. Eden Prairie, Minnesota: Bluedoor Publishing Company, 2006. Wingerd, Bruce. Rat Anatomy and Dissection Guide. Eden Prairie, Minnesota: Bluedoor Publishing Company, 2008.