Anatomy of the cecum of the laboratory mouse and rat.

The anatomy of the cecum of the laboratory mouse and rat was studied from a comparative standpoint. The topographical situation, mesenterial connections and arterial supply to the ceca were examined macroscopically. Dried specimens were made to study the morphological form and internal structures. Microscopically, at the light, transmission and scanning electron microscopic levels, the characteristic structural aspects of the ceca of both species were observed. The mucosa of the mouse cecum is arranged in soft-contoured, looped configurations (SEM), which appear as wide-opened crypts light microscopically. The rat has a similar appearance except that the configurations are more densely arranged and the crypts narrower. With TEM, the cecal epithelial cells of both species display typical features of intestinal absorptive cells. The observations made in the rat and mouse are compared with each other and with other species where detailed information is available.