Foothill Anatomy & Physiology Your Name ______
Cat Dissection Guide Group Members ______
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Dissection Rules
1. NO GOOFING AROUND. We are using sharp instruments, and the chemicals that the cats are preserved in can be harmful if they get in your eyes or mouth. Move slowly and carefully in the lab area. Don’t be in a rush.
2. WEAR GLOVES AND EYE PROTECTION. Again, the preservative can damage your eyes and may damage skin if not rinsed off. You must have either glasses or lab goggles. Students with contact lenses are strongly encouraged to wear glasses this week. If you get preservative on you or your clothing, DON’T PANIC. Just rinse with water and you’re fine.
3. NO FOOD OR DRINK WHATSOEVER. You will have chemicals on your hands, so no eating or drinking (even water) in the classroom this week.
4. BE RESPECTFUL. Be respectful of your classmates who may be sensitive to animal use, and be respectful to your cat specimen. Cutting or removing parts unnecessarily is not cool and will be grounds for a reduced grade.
5. WORK EFFICIENTLY BUT DON’T RUSH. You have limited time to complete all of the activities in this dissection, but make sure you read directions before cutting and do things in the order directed so that you do not make mistakes. Don’t waste too much time being meticulous, but don’t get reckless either.
Initial Preparation
1. Remove your cat from the plastic bag and place it on the lab table with a bed of paper towels underneath. Do not empty the fluid from the bag. This preservative will keep your cat moist when stored.
2. Fill out an index card with the names of all group members on BOTH sides with a permanent marker. Put this index card inside the large, clean bag to identify your cat specimen
3. When you are finished each day, you will return the cat to the bag it came in, and place this bag inside the larger plastic bag with the index card in it. You will close seal the outside bag tightly with rubber bands.
3. Identify whether your cat is male or female by looking on the card that came inside the bag with the specimen. If the symbol is a circle with an arrow sticking out the top, your cat is male. If the symbol is a circle with a cross sticking out the bottom your cat is female.
Our cat is MALE / FEMALE.
4. Lay your cat on its back (paws in the air). We will refer to this as the cat’s anatomical position. Towards the head will be superior, towards the tail inferior. Towards the belly or ventral surface will be anterior and towards the back or dorsal surface will be posterior. We will use these terms to maintain consistency with human anatomy.
The Muscular System – Muscles of the Cat Thigh and Calf
1. Carefully remove the fur and skin from the left thigh of your cat. Peel the skin back down the leg so that the muscles of the thigh and calf are visible.
2. Use the blunt probe and your fingers to get between and separate the individual muscles of the thigh and calf.
3. Using the lab manual provided at your lab table, refer to page 182-199 and identify the 11 muscles listed below. When you are confident you can identify all of them, call over your instructor to check your answers. Your instructor will sign off on each correct muscle. You will have ONE second chance to identify any you missed. You will not receive credit for muscles that your instructor must show you.
Muscles to be identified:
Sartorius ______
Gracilis ______
Vastus Lateralis ______
Rectus Femoris ______
Vastus Medialis ______
Adductor Femoris ______
Semimembranosus ______
Semitendinosis ______
Biceps Femoris ______
Gastrocnemius ______
Soleus ______
The Abdominal Cavity – Examination of the Internal Organs
1. Lay your cat on its back. Make an incision through the skin and muscle at the midline of the ventral surface of the cat from a point between the legs.
2. Using scissors, cut along the midline towards the head, until you reach the diaphragm. Don’t cut through the diaphragm just yet.
3. When you reach the diaphragm level, cut laterally both to the right and left, following the contour of the diaphragm and ribcage, which is a downward curved line. Also cut laterally at the beginning of your first incision line so that you may fold the two flaps of skin and muscle to the side and expose the entire abdominal cavity.
The Greater Omentum
1. Notice the membranous greater omentum, which covers the abdominal cavity. Your cat may have yellowish fat deposits on the omentum. Describe the appearance of the greater omentum:
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2. Peel the omentum away from the organs. It should come free at the bottom and peel upward like a shirt. You may need to cut the omentum where it is attached at the top. What organs does directly attach to? ______
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3. Remove and discard the greater omentum.
The Liver and Gallbladder
1. Locate the liver on the right side of the abdominal cavity (remember, the cat’s right). The organ is large, dark brown and smooth. It is made up of a number of lobes. Using the picture on p. 302 in the lab manual, identify the two lobes you can see on the surface.
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2. Carefully lift the lobes of the liver and see if you can find the gallbladder. It’s hard to miss. It’s a little dark green bag centrally located beneath the lobes of the liver. Using the scissors, cut into the gallbladder and squeeze out the contents. What is the greenish, yellow fluid that comes out?
______
What is the function of the fluid?
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3. See if you can find the common bile duct that carries bile from the liver and gall bladder to the digestive tract. Follow the duct and see where it enters the digestive system. What part of the intestine is this?
______
4. Carefully remove the liver and gallbladder. You may have to cut through some membranous tissues to do so, but try not to remove anything but the liver and gallbladder.
Digestive System
1. You can now examine some of the components of the digestive system. The esophagus is still obscured by the thoracic cavity, but you should be able to find where it passes through the diaphragm and enters the stomach.
2. Locate the stomach. Make a lengthwise incision in the stomach and observe the stomach contents. Can you identify anything that your cat ate shortly before it died?
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3. Remove the food contents from the stomach and discard. Look at the inner surface of the stomach. Is it smooth or rippled?
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If your cat’s stomach is distended (stretched out from food) you may not see ridges, but they are usually there. What are the ridges on the inside of the stomach called?
______
4. Follow the stomach to locate the duodenum of the small intestine. See if you can locate the ducts that enter the duodenum from the liver and pancreas. What do these ducts carry into the small intestine?
______
5. Carefully remove the pancreas from the abdominal cavity. It looks like a white spongy tongue and is located inferior to and slightly behind the stomach. What are the two functions of the pancreas?
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6. Gently pull the small intestines out of the abdominal cavity without cutting. You should notice that there is a pretty tough membrane attached to the entire length of the small intestine that has blood vessels and nerves embedded within. What is this membranous structure?
______
7. Make a lengthwise incision in the small intestine about one to two inches down the intestine from the duodenum. Look inside the intestine and clear out any digestive debris (chyme). Are there any ridges on the inside of this region of the small intestine? YES / NO
If so, are they parallel or perpendicular to the movement of food? PARALLEL / PERPENDICULAR
What are these ridges called? ______
8. Follow the small intestine down and see if you can find the location where the narrow-diameter small intestine transitions into the wider-diameter large intestine. What is the muscle ring that divides these two regions called?
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9. Follow this large intestine until it heads down through the pelvis and exits the body. What is this region called?
______
10. Now you’re going to carefully remove the entire digestive tract. Cut through the region you observed in the last step as close to the pelvic floor as possible.
11. Now go back to the stomach and cut the esophagus as close to the diaphragm as possible (we’re still not going into the thoracic cavity yet).
12. You will complete the removal of the digestive tract by carefully cutting through the mesentery and any other connective tissue that is holding the stomach and intestines in place. Lift the digestive tract out of your cat and place it on the dissecting tray.
13. Measure the following regions:
Stomach length: ______width at widest point: ______
Small Intestine length (you may have to remove mesentery to measure): ______
Large Intestine length: ______
Total Length: ______
14. Using your scissors, cut open the entire digestive tract lengthwise with one long incision. Examine the interior surface of the digestive tract from the end of the esophagus to the end of the large intestine. Use the dissecting microscope if necessary to get a closer look. Describe any differences you see in the lining of the digestive tract from region to region.
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The Spleen
1. The spleen is a darkly colored, tongue-shaped organ that is positioned near the pancreas, on the left side of the cat. Remove the spleen. Using your textbook, identify the function of this organ:
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Urinary System – Kidneys and Bladder
1. Find the kidneys along the back surface of the abdominal cavity. Find the hilus of the kidney (where the blood vessels and ureter join the kidney on its medial edge. Follow the ureters down to the urinary bladder. In the space below, draw the urinary system as it appears in your cat. Label the following structures – kidneys, adrenal glands, renal arteries, renal veins, ureters, urinary bladder, urethra (if visible):
2. Now carefully remove one whole kidney (right or left). You will have to cut through the renal artery, renal vein, renal nerve and ureter to fully free the kidney from the abdominal cavity. You may also have to cut through the wall of the abdominal cavity, as the kidneys are retroperitoneal.
3. Place the kidney on your dissecting tray. Cut the kidney frontally, so that there are front and rear halves. Try to cut the kidney right down the middle, where the ureter exits the kidney on its medial edge. Use the scalpel for this cut to make it as smooth and clean as possible.
4. Using the dissecting microscope, look at the inner surface of one half of the kidney. Draw what you see, and label the following structures if you can identify them – adrenal gland, renal cortex, renal medulla, renal pyramids, renal columns, minor and/or major calyces, renal pelvis, and ureter:
Thoracic Cavity – The Heart and Lungs
1. To open the thoracic cavity, you will use your scissors to cut through the ribcage, just to the right or left of the midline. A midline cut would go through the sternum and would be very tough. If you cut just lateral of the sternum, through the ribs, it will be an easier process. Cut from the diaphragm, up as high as you can towards the lower jaw. Put the more blunt point of the scissors inside, to avoid damage to the thoracic organs.
2. Make lateral cuts up near the neck towards the shoulders, to open the chest cavity. You may need to carefully separate the thoracic cavity lining (the parietal pleura and parietal pericardium) from the ribcage as you peel it back.
3. You should now be able to identify the two lungs and the heart. Notice the tough membrane that surrounds the heart. What is this membrane called?
______
4. Remove the membrane from step 3, exposing the heart and its blood vessels. See if you can identify the following blood vessels that are attached to the heart: aorta, superior and inferior vena cava, pulmonary arteries, pulmonary veins.
5. Carefully remove the heart by cutting the blood vessels and any remaining pericardium, and place it on your dissecting tray. Now that you’ve removed the heart, see if you can identify the any major blood vessels you could not see previously. Describe what you see:
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6. Cut the heart horizontally through the ventricles so that you have superior and inferior halves. Look at the sectioned surface under the dissecting microscope and draw what you see below. Label the ventricles:
8. Do you notice that one of the walls of one ventricle are thicker than the other? Why is this so?
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7. The heart and blood vessels have been injected with a rubbery dye. Which color represents oxygenated blood and which color represents deoxygenated blood?
OXYGENATED ______DEOXYGENATED ______
8. Now look at the lungs. Draw what you see, and label any of the following structures that you can – diaphragm, apex, base, cardiac notch, primary bronchi, trachea:
9. Cut horizontally through one of the thicker portions of one lung about halfway down its length. Remove the lower piece and look at the cross-section under the dissecting microscope. Draw what you see and label any of the following structures that you can – bronchus, pulmonary artery, pulmonary vein.
10. Carefully remove the lungs, bronchi and trachea and see if can identify the esophagus. Have your instructor sign off that you’ve identified the esophagus below:
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Extras
You have now completed the required dissection. If you have finished early and there is still time, please look for the following organs or structures. When you have found them, call over your instructor to sign on the line confirming that you have correctly identified each structure:
Sciatic Nerve ______Larynx ______
Femoral Artery ______Gonads (Testes or Ovaries) ______
Femoral Vein ______
Achilles Tendon ______
Descending Aorta ______
Inferior Vena Cava ______