POSTNATAL-DEVELOPMENT OF ALIMENTARY CANAL IN OPOSSUM .3. SMALL-INTESTINE AND COLON

  • 1 January 1977
    • journal article
    • research article
    • Vol. 123  (FEB) , 21-45
Abstract
Opossums (Didelphis virginiana) (105) were used to examine the postnatal development of the small and large intestines. Pouch-young were divided into 17 groups according to their snout-rump lengths. Four adults were also used in the study. Tissues were studied by light microscopy, scanning and transmission electron microscopy. Quantitative studies included measurements of the depth of the mucosal epithelium, the depth of the crypts and the lengths of the intestinal villi. Paneth and goblet cells were counted and reported as the number of cells per 1000 epithelial cells. The developing colon was assessed at the same stages and in a similar fashion. The number of mitotic cells and goblet cells were counter per 1000 epithelial cells. Histochemical tests were conducted. The epithelium of the entire small intestine is modified for absorption until just prior to weaning. The principal intestinal lining cells show an extensive apical endocytic complex, large supranuclear vacuoles and numerous cytoplasmic inclusions. Intestinal epithelial cells of the colon appear to be modified for absorption during the first 2 wk after birth. In contrast to the small intestine, goblet cells are numerous in the colon early during the postnatal period. The significance of macromolecular absorption and the possibility of passive immunity being transmitted in the opossum during suckling, are discussed and related to similar events that occur in the suckling young of several eutherian species. The possible functional significance of 2 large membranes that develop in the lamina propria of the intestines after weaning is discussed.