Digestive System Dissection

Transcription

1 Digestive System Dissection THE TERMS YOU NEED FOR THE PRACTICAL ARE IN THIS DISSECTION GUIDE. Instructions: Do one of the 2 respiratory dissections, and then the digestive dissection. Wordlist for cat digestive tract dissection Oral cavity Hard palate Soft palate Uvula Tongue Oropharynx Pharynx Parotid salivary gland Submandibular salivary gland All 3 tonsils Gingivae Incisor Canine Neck Enamel Esophagus Stomach Body Fundus Cardiac region Greater& lesser curvatures Cardiac valve/junction Pyloric Pyloric sphincter valve Rugae (if stomach is not distended) Duodenum Ileum Jejunum Peritoneum (visceral & parietal) Villi Liver Gall bladder Common bile duct Cystic duct Hepatic duct Falciform ligament Spleen Pancreas Cecum Ileocecal valve Ascending colon Transverse colon Descending colon Rectum

2 C) Digestive Tract Dissection (ALL of class) Unfold the protective layer which covers the intestines (Greater Omentum). You may be able to simply unfold this structure away from the intestines; however, it may be removed by cutting it loose from its attachment on the stomach, pancreas and spleen. If you remove the Greater Omentum, please save it with your cat. ID the diaphragm. Locate the stomach, the pink J-shaped structure. In order to see the different parts of the stomach, take your scissors and cut along the greater curvature. (If you are lucky you will see what the cat had for breakfast the day it died. And maybe some parasitic worms!). Clear out any food, hair, or intestinal parasites (worms), using a paper towel if necessary. Locate where the esophagus enters the stomach. From the inside of the stomach, it looks like a pucker or small volcano near the top of the stomach. Identify the Fundic, Cardiac, body and pyloric regions. I.D. The rugae. NOTE: if the stomach was filled with food when the cat died, the rugae may not be readily visible, as they get smoothed out when the stomach is distended.

3 Locate where the pyloric sphincter runs into the first part of the small intestine, the duodenum. The valve can be easily found at the end of the stomach, as it feels like a hard knuckle. Cut through the pyloric sphincter valve from the side, as it enters the duodenum. Basically, you are doing a frontal section (see following image). Spread apart the small intestines, noticing the mesenteries. In order to see the intestines better, unfold the loops by cutting through the connective tissue and blood vessels. The small intestines should unwind like a hose. By the time you cut all the loops loose, you should be able to follow the path that the chyme travels as it runs through the length of the small intestine. Locate the pancreas in the crux of the duodenum. WARNING: the pancreas won t look like much on the cat...just some glandular tissue running up towards the stomach. Notice how thin the pancreas is. The pancreatic duct is inside. You can dissect out the pancreatic ducts by getting a fairly sharp scalpel and shaving away the pancreas las seen in the image. However, it will not be on the lab practical as the cat s pancreas is so thin you often can t find it.

4 Locate the liver and gall bladder. ID the falciform ligament. Find the 3 ducts: hepatic, cystic and common bile. You will have to clean away the connective tissue surrounding them before you can individually distinguish all 3 ducts. You can follow the common bile duct all the way to the entrance at the duodenum (the ampullae). NOTE: Sometimes the gall bladder is really implanted into the liver. You can dissect out the gall bladder, removing it from the liver, quite easily BUT DO NOT COMPLETELY REMOVE IT. Simply use the tip of your scalpel to clean away the connective tissue holding it in place. About ½ way down the intestines, cut off a piece of the intestinal tube about 1-2 inches long. Using your scissors, cut open the tube. Notice the inner wall looks like shag carpeting...these are the villi.

5 Find the ileocecal junction. Again, the valve will feel like a hard knuckle. To see the valve clearly, cut off the top of the cecum like so: Clean out any fecal matter, using a paper towel and a little water if necessary. Look straight down; you should see another little pucker : Your large intestines are probably no longer in correct anatomical position. See if your group and put them back where they go, identifying the cecum, ascending colon, transverse colon, descending colon, and rectum. Cats do not have an appendix or a sigmoid colon. Notice that the rectum leaves the body just behind the urinary bladder.