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1 The$Pig$ $ Dissection$Manual$ (you%only%get%one,%don t%lose%it)% DIGENISCLASSES2016 Name: Block:

5 Fetal Pig Lab Check off each organ/structure as you locate it on your pig. Answer questions where indicated. I. External Anatomy of the Pig A. Age: 1. By using this table and measuring the length of your pig in centimeters you can determine the approximate age of the pig. Measure your pig from crown to rump as shown in the diagram (this does not include the length of the tail). 2. How old is your pig? (approximate) Size in cm Age (in days) Full Term ( ) B. Body: Check off each organ/structure as you locate it on your pig. head and neck trunk: part of body from base of neck to pelvis...basically everything except head, tail & appendages tail appendages (limbs) 1. Head and Neck of Pig: eyes ears nostrils mouth larynx 2. Appendages: digits 3. Trunk: thorax sternum abdomen Are they open yet? Can you see the tongue? Not visible yet but feel for the Adam s Apple under the skin in the pig s throat area. You will see this when the throat area is dissected later. How many digits does the pig have on each foot? How many digits does the pig walk on, on each foot? The body cavity that extends from the neck to the diaphragm (basically, the chest area). The bone in the center of the chest to which ribs attach in front (you can feel for it). Body cavity posterior to the thorax. Pig Packet 2016 Page 1 of 10

6 umbilical cord Still partially attached to the ventral side of the abdomen. This used to be attached to the placenta in the womb of the mother. mammary glands anal opening 4. Sex Determination: Nipples or teats; are found on the ventral surface. How many mammary glands does your pig have? Why are there so many? Located under the tail. You are responsible for knowing the structures on both the male and female pig. First, determine the sex of your pig by reading both descriptions below and matching one to your pig. Then, find a group to partner with that have a pig of the opposite sex. You will be responsible for showing each other the relevant parts later on. Female External Anatomy urogenital opening Found immediately ventral to the anal opening; this opening can be recognized by the fleshy knob next to it (this knob is the vulva). Male External Anatomy urogenital opening Look for a small hole just posterior to the base of the umbilical cord. scrotal sacs penis What is the sex of your pig? Two slight swellings posterior to the hind legs. This is a muscular tube structure lying under the skin, running posteriorly from the urogenital opening. You can feel this under the skin. It is not very obvious. Name of Partner Group: (they should have opposite sex pig) II. Digestive System Do male pigs have mammary glands? (look at Partner Group pig if yours is female) You are about to begin your examination of the alimentary canal (consisting of the mouth, esophagus, stomach, small intestine, and large intestine) and a number of glands (liver, pancreas). A. Mouth 1. This is the entrance to the digestive system. Find the following: tongue papillae teeth esophagus Bumps on the surface of the tongue. Some may only be partially erupted. Look carefully in the mouth and/or feel carefully with your finger or probe. Not visible yet. Wait for later dissection of the throat. Pig Packet 2016 Page 2 of 10

7 B. Abdominal Cavity Now you are ready to examine the viscera (the internal organs) of the abdominal cavity. ** Read through all the steps in this section first, then go through them again, performing each step. ** 1. Place the pig on its dorsal side (ventral side up). You may wish to tie your pig s forelegs at this point, as demonstrated in class, for greater ease in handling the pig. 2. Pull up on the umbilical cord in order to lift the thin wall of abdomen, holding it away from the internal organs. Carefully insert the fine point of the scissors, or the scalpel, through the wall of the abdomen where lifted, just anterior to the base of the umbilical cord (see incision diagram on next page). Cut through the skin and muscle to the abdominal cavity. Always cut up so as to not injure internal organs. If you don t know what this means, ask. 3. Cut in a straight line down the midline of pig from umbilical cord to bottom of sternum. DO NOT CUT THROUGH RIBS or DIAPHRAGM (it s okay if you do, but try not to). 4. Refer to diagrams on next page for help. Cut around both sides of the umbilical cord. The umbilical vein (sometimes blue due to injected plastic) extends from the inside of the umbilical cord to the liver, the large brown organ in the abdomen. You will have to cut through the umbilical vein, but make note of it first. 5. FEMALE ONLY: Carefully join the cuts from either side of the umbilical cord at a point just posterior to the cord. The umbilical cord should still be attached to your pig, however (Internally, the urinary bladder is still attached to the base of the umbilical cord, even though you have cut through the skin and muscle.) Now continue your cut down between the legs. MALE ONLY: Do NOT join the cuts from either side of the umbilical cord (as was done in female). Instead, continue the two cuts separately (posteriorly) between the hind legs as shown in diagram. This is to avoid cutting the penis which is just below the skin. Written instructions continue on next page... Incisions to be made in numerical order for dissection of abdomen For MALE Pig Only: For FEMALE Pig Only: Pig Packet 2016 Page 3 of 10

8 6. In both cases, just in front of the hind legs, cut laterally through the body wall on either side. Make another two lateral cuts at the top of the abdomen, exposing but not damaging the diaphragm. You should now have two flaps which can be opened sideways to expose the internal organs of the abdomen. 7. Remove and throw away any stray pieces of red or blue plastic. Drain and gently rinse out the abdominal cavity of your pig. This may be easier to do at a large sink. (You may have a great deal of brown fluid in the abdominal cavity if the bile from the liver has escaped into this area. Just rinse as much away as possible.) You are now ready to find the following abdominal organs/parts: liver gall bladder stomach pancreas pyloric valve small intestine large intestine Made of two parts: colon appendix spleen Large reddish brown organ at the anterior end of the abdominal cavity. Gently lift liver. You will see a greenish or colorless sac on the posterior side of the liver. This is where a digestive juice called bile is stored. A bag-like structure, best seen by lifting liver further. Lift the stomach to find this. It is a gray or yellowish mass that looks a bit like cauliflower. As part of the digestive system, the pancreas secretes digestive enzymes. It also secretes the hormone insulin. A hard lump of muscle at the exit of the stomach where it connects to the small intestine. Feel for this. (Also called pyloric sphincter.) Loose mass of tubing leading directly from pyloric valve; connects with the large intestine. This is usually partly beige / partly greenish. Darker-colored, usually green mass of tubing found in abdomen. First part of large intestine; is tightly coiled and often green in color. rectum Posterior part of large intestine that leads to the anal opening. It is straight, not coiled. To see it, you must push aside the colon and small intestine. anal opening A little foot-like pouch which forms at the junction of the small and large intestine. (sometimes tricky to find - follow small intestine along until you find where it meets with the large intestine) A long, flat, brownish organ located near the stomach on the pig s left (not a digestive organ; the spleen stores blood and functions in the immune system). Located just under the tail. What is missing? How does food get from the mouth to the stomach? We ll see this later. III. Urogenital System The urinary system is closely linked to the structures of the reproductive system in both the male and female pig. When we refer to both these systems collectively we use the term urogenital. **Remember, regardless of the sex of your pig, you are expected to eventually know the systems of both the female and the male. Pig Packet 2016 Page 4 of 10

9 A. Urinary (Excretory) System kidneys ureters urinary bladder urethra B. Female Reproductive System Two bean-shaped structures located against the dorsal wall of the abdomen. To expose these, use a probe to tear/pull away the shiny membrane (peritoneum) that covers them. Thick white tubes running posteriorly from the kidneys to the urinary bladder. These carry the urine from the kidneys to the urinary bladder. You may have to tear away more membrane to expose these. Trace these from the kidneys all the way to where they attach to the urinary bladder. The storage organ for urine. This is an elongated sac lying between two large blood vessels called the umbilical arteries (probably red/pink due to injected plastic). The outermost tip of the urinary bladder is attached to the umbilical cord, though there is no opening of the bladder at this point. ** Look for the entrance of the ureters into the bladder at the base of the bladder, opposite the umbilical cord end. point of joining of ureters and bladder two umbilical arteries (red/pink, flanking urinary bladder) The tube that runs from the urinary bladder: into the urogenital sinus in the female pig and through the penis in the male pig (see Reproductive Systems for more on these structures). You probably will not see much of the urethra until you dissect the reproductive system. 1. Flip the urinary bladder & umbilical cord toward the pig s anterior end. At the posterior end of the bladder, insert the end of the probe and push upward to feel for the hard pelvic bone. (The bladder appears to be disappearing into this hole in the pelvis.) 2. With a scalpel, carefully cut through the pelvic bone between the hind legs so the legs will lie flat. Be careful not to damage the tissues lying beneath the bone -- you can place the probe beneath the pelvic bone and use it as a guide to help you with this. 3. Once you have cut through the pelvis, flip the umbilical cord and bladder back toward the posterior end in order to start at the beginning of the female reproductive system. ovaries uterine tubes uterine horns uterus Two small white bean-shaped bodies in the lower part of the abdomen. You may have to move the intestines aside in order to see them. Lift an ovary with a probe and look on the underside of the ovary for a tiny, tightly coiled tube. The uterine tubes broaden into thicker tubes, the uterine horns. These are homologous to the fallopian tubes in humans. In the pig, this is where embryos develop (not in the body of the uterus, as in the human). This allows for multiple births (large litter size) in the pig. Somewhat V-shaped area, at the joining of the two uterine horns, just anterior to the base of the urinary bladder. Unlike the human, the uterus is not the site of embryo development for the pig -- it is just a birth canal. Pig Packet 2016 Page 5 of 10

10 vagina A thick muscular tube which is a posterior continuation of the uterus. Use the probe to explore where the uterus disappears under the bladder. You will have to push apart the severed pelvic bone and carefully clear away membranes connecting the urethra and vagina to each other so that you can trace the uterus to the vagina. Note that the vagina lies dorsal to ( below ) the urethra, which extends from the base of the urinary bladder toward the pig s posterior. There is no obvious distinction marking the transition from uterus to vagina. urethra* urogenital sinus Tube which extends posteriorly from the base of the bladder, and joins with the vagina to form the the urogenital sinus in the female pig. *Not a reproductive structure in female - this is part of the urinary system. Located about an inch or less from the end of the pig; the vagina joins with the urethra to form the urogenital sinus. This tube finally leads to the urogenital opening in the female pig. urogenital opening Opening to urogenital sinus; found ventral to the anal opening in female. vulva Fleshy protuberance found at / covering urogenital opening. Also called the urogenital papilla. List, in order, the structures an egg must travel through to exit the female pig s reproductive system: ovary --> uterine tubes --> --> --> --> --> urogenital opening. List, in order, the structures urine must travel through to exit the female pig s urinary system: kidney --> --> --> --> --> urogenital opening. C. Male Reproductive System scrotal sacs processus vaginalis testis (pl. testes) epididymis ductus deferens Two slight swellings at the posterior end, between the hind legs. This is an elongated membranous sac that contains the testis and other reproductive structures. There is one in each scrotal sac. To find these, cut the surface skin and muscle of the scrotal sacs. The processus vaginalis can now be slipped out. Carefully do this on each side of the pig. Carefully cut open the membrane of the processus vaginalis to reveal the small tan bean-like organ where sperm are produced. Tiny, tightly-coiled white tube that runs in a C-shape alongside the curve of the testis. This is where sperm are stored. A thin white cord that resembles flat dental floss. This is a continuation of the epididymis, leading from the epididymis to the urethra. Follow the ductus deferens as it loops over the ureter near the attachment of the ureter to the bladder. This cord joins to the urethra on its dorsal wall. (Note: you probably will not be able to see the attachment of the ductus deferens to the urethra -- it will appear to attach to the base of the bladder.) Pig Packet 2016 Page 6 of 10

11 urethra & penis The urethra is the tube leading from the base of the bladder to the urogenital opening. The last part of this tube is surrounded by the muscle of the penis (erectile tissue). Finding the first part of the urethra (near the bladder) may require cutting through the pelvic bone (see optional below). Finding the urethra as it passes through the penis is also a tricky dissection. Note that the penis (the muscle surrounding the latter part of the urethra) is INTERNAL in the fetal pig and since muscles are not well developed in the fetus, you will not find an obvious structure you can call the penis. Feel for the urethra/penis (a muscular tube) running under the skin just posterior to the umbilical cord. Remove the covering of the skin and trace the urethra through the pelvic bone. The urethra is a continuous tube that runs from the base of the bladder to the urogenital opening. Optional: Cut through the pelvic bone in the area between the top of the hind legs so that the legs will lie flat. Be careful not to harm underlying structures. Try to follow the length of the urethra from the base of the bladder, through the pelvis, back up under the skin (penile tissue) to the urogenital opening. List, in order, the structures an sperm must travel through to exit the male pig s reproductive system: testis --> --> --> --> urogenital opening. List, in order, the structures urine must travel through to exit the male pig s urinary system: kidney --> --> --> --> urogenital opening. IV. Respiratory System A. Dissection of the mouth Review the respiratory structures you have already observed: nostrils (nares) and mouth. To see the rest of the respiratory system from the entrance point to the body, use your scissors to cut the jaws as follows: 1. Direct the pointed blade (fine blade) of the scissors down the throat and starting at the corners of the mouth cut firmly all the way through the cartilage of the jaw, on both sides of the mouth. 2. Deepen your cuts until the mouth opens freely. As you cut deeper, re-angle your scissors so you are continuing your cuts down the throat. Careful not to damage the back of the throat. epiglottis A small white tab found deep in the throat, at the opening to the trachea (covering a hole called the glottis). This tab is made of cartilage. The jaw must be open very wide in order to see this. If you do not see it, you may not have cut the jaws enough OR it may be tucked into the glottis -- use your probe to find it. Where does the opening (the glottis) lead? Explore the rest of the respiratory system to find out Pig Packet 2016 Page 7 of 10

12 B. Dissection of the neck and thoracic cavity diaphragm Flat sheet of muscle at the base of the thoracic cavity, attached to body wall. This separates the thoracic cavity from the abdominal cavity. Before you open the ribcage, you may have to cut the diaphragm laterally, right next to and along the rib cage, in order to expose the thoracic cavity more clearly. Now cut through the rib cage with scissors on a line from the diaphragm to just to the right (or left) of the sternum (the breastbone) up to the pig s chin. Do not damage the delicate structures below. thymus gland* In the neck, where you have just dissected, find: larynx thyroid gland* trachea The thymus gland tissue fills much of the throat area and may extend over the heart. Confirm with the teacher that you have found this. Then you can remove some of the thymus to give you a clear view of the neck region. The thymus is part of the endocrine* system, not the respiratory. The voice box or Adam s apple; an enlarged white structure in the throat, found at the anterior end of the trachea. Reddish-brown bean-shaped structure at base of larynx. This is an endocrine* gland that produces hormones which control metabolism. This is not a respiratory organ. The windpipe, a tube leading from the larynx to the lungs. rings of cartilage You can find and feel these rings on the trachea. These rings help keep the trachea open for the passage of air. Without them, the trachea would collapse and air cannot pass through. esophagus** Push aside the trachea and note a smaller and more flexible tube lying dorsal to the trachea. This carries food from the mouth to the stomach and is not part of the respiratory system. The esophagus is part of the system. Why doesn t the esophagus need rings of cartilage also??? How does food move through the esophagus? By the process of: In the thoracic cavity, find: lungs C. Inflation of the lungs Spongy and un-inflated. Note the lobes into which they are divided. Cut a small piece of lung tissue and place in a beaker of water (there should be beakers in the shelves in the back of the room). Does the tissue float or sink? Why? Now, cut a small slit in the trachea, below the larynx (i.e. perform a tracheotomy on your pig) and place a clean straw down into the trachea and blow to inflate the lungs. You will need a good seal between the straw and the small hole you made for this to work. You should be able to see the inflation of the lungs and often a slight color change in the inflated tissue. Cut another piece of inflated lung tissue and place in water. Does it float or sink? Why? Pig Packet 2016 Page 8 of 10

13 V. Circulatory System (figures 9a, 9b, 10, 11) **NOTE: When you see the directions LEFT or RIGHT written in your lab manual or on a diagram, this refers to the pig s left and right, not yours. A. External anatomy of the heart (figure 9a) heart pericardium left ventricle right ventricle coronary artery right atrium left atrium Lies in the center of the chest between the lungs. Tough membrane covering heart. Remove it using scissors & forceps. Large chamber on the lower left side of the heart (the pig s left). Chamber on pig s lower right. (Pink) Artery running diagonally down the ventral side of the pig s heart from its upper left to lower right. Separates the two ventricles. Dark reddish brown flap on the anterior (upper) part of the heart, lying over the right ventricle. Also called the right auricle. Same as above except on left side. Also called the left auricle. Veins carry blood toward the heart from the rest of the body or lungs. Arteries carry blood away from the heart to the rest of the body or lungs. Blood in the veins is rich in (O2 or CO2?) and poor in. Blood in the arteries is rich in and poor in. Exceptions to this rule: Umbilical arteries and vein, Pulmonary arteries and veins. B. Blood vessels attached to the heart In our pigs, the blood vessels has been drained and injected with colored latex so they will show up better. The ARTERIES will appear PINK if they are thin-walled and WHITE if they are thick-walled. The VEINS will appear BLUE if well injected (because they are all thin-walled and show the color). pulmonary artery Large white artery leading out of the right ventricle, lying between the two atria. This branches into a left and right branch, one for each lung. aorta pre-cava post-cava Large white artery whose base is covered by the pulmonary artery. It leads out of the left ventricle, arches through the branches of the pulmonary, and turns posteriorly to head down through the thoracic and abdominal cavities. This part of the aorta is called the aortic arch. Also called the anterior vena cava. The large (blue) vein entering the right atrium. Also called the posterior vena cava. Lift the heart up and towards the head. The postcava is the (blue) vein that runs from the abdominal cavity, through the diaphragm, and into the right atrium. Pig Packet 2016 Page 9 of 10

14 C. Following the arteries & veins a bit further post-cava (abdominal cavity) thoracic aorta abdominal aorta (already mentioned above, also called posterior vena cava) Lift the organs of the abdominal cavity to one side and find the large blue vessel running up/down the back of the pig. Observe that it goes through the diaphragm and is the same postcava you saw entering the heart. Portion of the aorta that runs through the thoracic cavity. Push the heart and left lung toward the right side to see the large white vessel that runs along the dorsal wall behind the lungs, from the heart to the abdomen. Continuation of the thoracic aorta that runs into the abdominal cavity. Move the abdominal organs to see it. umbilical arteries You will find these to the right and left of the urinary bladder. They should be pink but sometimes the injection to these vessels is not complete and they may be un-injected (beige or dark brown) or misleadingly blue. These carry blood from the fetal pig to the umbilical cord. Is the blood in the umbilical arteries rich or poor in oxygen? VI. Endocrine System The endocrine system consists of isolated glands. These glands secrete chemicals called hormones. Look for & ID the following glands of the endocrine system: thymus gland thyroid gland pancreas ovaries / testes You removed much of this when you dissected the neck and thoracic region. It is large, irregularly shaped and light-colored. This is part of the immune system and helps to fight off disease and infection. Small, brownish, bean-shaped gland located in the throat. The function of the thyroid is secretion of hormones which affect the metabolic rate. Also a digestive organ. Located directly under the stomach. It secretes many digestive enzymes, as well as the endocrine hormones insulin and glucagon. You located these when you dissected the reproductive system. Ovaries secrete estrogen and progesterone while the testes secrete testosterone. These hormones are responsible for sexual development and reproduction. Pig Packet 2016 Page 10 of 10

Fetal Pig Dissection. Introduction:

Fetal Pig Dissection. Introduction: Fetal Pig Dissection Introduction: Today, we begin a new chapter in our study of biology. In the first half of the year we looked at how the smallest units of life work, reproduce and pass on their genes.