SCANNING ELECTRON-MICROSCOPIC STUDY OF INTESTINAL-MUCOSA OF THE NILE CROCODILE (CROCODYLUS-NILOTICUS)

As part of an ongoing study of the intestinal tract of the Nile crocod ile Crocodylus niloticus, the appearance of the small intestinal mucos a was examined using a scanning electron microscope (SEM). The duodenu m displayed ridge-like and complex primary folds, both of which were a rranged in a longitudinally directed zigzag pattern. The two types of folds alternated with each other, with the second type following the z igzag contours of the first. The folds were covered with polygonal- an d dome-shaped epithelial cells. The latter cell type was less common a nd was restricted in location to the proximal two thirds of the mucosa l folds, Both types of epithelial cells were covered with stubby micro villi which displayed a distinct linear arrangement. Goblet cells were present between the absorptive cells. In the jejunum the basic patter n of the folds persisted except that both types of primary folds becam e tall and leaf-like. The angle of the zigzag pattern was less acute t han in the duodenum. In the ileum the two types of alternating folds d ecreased in height and were arranged in a longitudinally directed wave -like fashion. The zigzag mucosal folds of the small intestine ended a bruptly at the ileorectal junction. The rectum displayed low, irregula r folds which formed occasional large, puckered, rosette-shaped struct ures. The particular arrangement of the intestinal folds fulfills the dual function of promoting the absorptive process and facilitating the smooth passage of the intestinal contents. (C) 1995 Wiley-Liss, Inc.