DUODENUM - Slide 127 (dog)
Find an area that is cut as true as possible, and find identifying characteristics: (1) goblet cells, villi, crypts of Lieberkuhn (intestinal glands) in the mucosa; (2) mucous Brunner=s glands in the submucosa. The Brunner=s glands are much less abundant here than in the previous slide, giving you a clear idea of the extent of each individual gland. Possibly your section shows the emptying of a duct of Brunner=s gland into the base of a crypt of Lieberkuhn. Can you identify the original level of the duodenal lumina surface, i.e., the level from which villi project and intestinal glands invaginate?
Notice the subtle difference in the way the connective tissue fibers of the submucosa and the muscle cells of the muscularis externa take the eosin stain. Collagen tends to stain a brighter, more intense pink than does cytoplasm. Using this color difference, can you pick out the muscle of the muscularis mucosae?
In the submucosa look for blood vessels and parasympathetic ganglion cells. Can you also see evidence of ganglion cells between the two layers of the muscularis externa? Has your section been taken from the adventitial or serosal surface of the duodenum?