Comparative Medicine Branch

Virtual Mouse Necropsy

Step 6: Intestines, Stomach, Spleen, and  Pancreas

Gross Anatomy of Male Mouse After Gastrointestinal Tract Removal

1. Salivary Gland
2. Rim Cage
3. Diaphragm
4. Liver
5. Spleen
6. Pancreas
7. Forestomach
8. Glandular Stomach
9. Kidney
10. Ascending Colon
11. Male Urogenital System

The next obvious group of tissues to tackle is the intestines and all other organs that are attached to them.

1. Sever the intestines from the body as far down as possible on the colon.
2. If you want to preserve the rectum and colon, it may be beneficial if you simply cut the skin around the anus.
3. Free the intestines from any fatty anchors until you reach the stomach.
4. The caudate lobes of the liver are going to be on the lateral sides of the stomach. You must cut the connective tissue carefully to leave the liver intact.
5. Cut the esophagus directly above the stomach in the abdominal cavity, leaving 0.25-0.5 cm of esophagus connected to the stomach. At this point, the entire gastrointestinal tract can be removed from the abdominal cavity.

Intestines

Gross Anatomy of Gastrointestinal Tract Right Side

1. Esophagus
2. Stomach
3. Duodenum
4. Jejunum
5. Ileum
6. Cecum
7. Ascending colon
8. Descending colon
9. Rectum

Starting at the rectum/colon, unzip the coiled intestines by pulling gently, using your scissors for help whenever you feel it is necessary. As you do so, check the surface of the intestines for enlarged Peyer's patches. There are many different parts of the intestine, but the majority of them cannot be differentiated from each other grossly.

Pancreas/Spleen

1. At one point, the ease with which the intestines can be pulled apart will change as you reach the pancreas. The pancreas is tan in color and can be easily differentiated from the surrounding fat. First, cut the stomach away at the duodenal junction and remove the spleen, placing the spleen in preservative.
2. Cut a section of the small intestine to which the pancreas is attached, using the intestine as a handle.
3. Spread the pancreas flat on a piece of paper towel. Within the tissue lie the pancreatic lymph nodes, which are identifiable only if enlarged.
4. Once again, place the piece of paper in formalin.

Stomach

If you wish to inflate the stomach,

1. Fill your syringe with your preservative and insert it into the duodenal junction.
2. Inject the fixative as you hold the needle in place with forceps.
3. On removing the syringe, some leakage may occur, but most of the fixative will remain in the stomach.

Fixation and Trimming Protocol for Stomach

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