Digestive organs of the abdomen
Next we will examine the abdominal organs. The most conspicuous organ in the abdominal cavity is the liver, which fits under the dome of the diaphragm. The stomach lies posterior to the liver on the left hand side of the body (remember, this means the specimen's left, not yours). Locate the spleen, a reddish organ which lies along the left side of the stomach. The spleen is actually part of the circulatory system; it is involved with the production, storage and destruction of red blood cells, and in the immune response.
Examine the stomach more closely and notice that the stomach wall is thickened where it joins the small intestine. This region is the pyloric sphincter, a thick band of circular muscle which controls passage of food from the stomach to the intestine.
Now return to the liver and look at its posterior surface. You should be able to see a greenish sac, the gall bladder. The gall bladder acts as a storage organ for bile, which is secreted by the liver. Bile is not a digestive enzyme, but it is important in digestion because it emulsifies (breaks up) fat so that it can be more easily digested. Bile is also released into the duodenum via the bile duct, which you should be able to locate between the gall bladder and the duodenum. You may have to dissect away some of the visceral peritoneum to see it clearly.
In the previous two images, the first part of the small intestine, the duodenum was visible leading away from the stomach at the pyloric sphincter. It crosses to the left side of the body, turns toward the stomach, and then turns posteriorly. This point is considered the beginning of the jejuno-ileum, but you will not see any demarcation between the parts. The next image shows the coils of the small intestine as they are spread apart. Notice that they are supported by the mesentery, which contains several blood vessels which will be studied next week.
Next, locate the pancreas in the loop of the small intestine. You will be able to identify it by its lobulated, cauliflower-like surface. Remember that the pancreas is both an exocrine gland, producing digestive enzymes, and an endocrine gland, producing the hormones insulin and glucagon. The digestive enzymes pass to the duodenum through a small pancreatic duct, but this will be difficult to see in your specimen.
The small intestine eventually enters the large intestine, or colon. At the point where it enters, the muscles of the colon wall form the ileocecal valve, which prevents material from reentering the small intestine. Notice that a part of the colon forms a blind sac, the caecum, to one side of the ileocecal valve. Like the small intestine, the colon is also tightly coiled. The terminal portion of the large intestine is the rectum. Most of the rectum lies deep within the pelvic cavity, and will be seen later in this dissection. The rectum opens to the body surface at the anus.