POSTNATAL-DEVELOPMENT OF ALIMENTARY CANAL IN OPOSSUM .2. STOMACH

  • 1 January 1976
    • journal article
    • research article
    • Vol. 122  (DEC) , 499-519
Abstract
Opossums [80] (Didelphis virginiana) were used to examine the postnatal development of the stomach. The pouch-young opossums were divided into 10 groups according to their snout-rump lengths. Four adults also were used. Tissues were studied by light microscopy and scanning and transmission electron microscopy. Calibrated pH papers were used to determine the pH of stomach contents. Quantitative studies of the gastric mucosa were made using sections of Epon-embedded material. The depth of the mucosa and of its constituent parts, the number of mitotic cells in the lining epithelium and the numbers of parietal cells, chief cells and mitotic figures in the glandular epithelium were determined. Histochemical tests were conducted. The formation of fovea and gastric glands occurred simultaneously during the postnatal period. During the first 60 postnatal days the developing gastric glands were composed of undifferentiated cells, parietal cells and scattered endocrine cells. Chief cells were not present until just prior to weaning. The pH of stomach contents ranged from 6.0-6.5 until weaning, when it dropped to 2.0-2.5. The surface lining cells contained a considerable amount of lipids during the first 3 wk after birth, which may indicate that the gastric mucosa was involved in the absorption of lipids during this period, although the mode of absorption appeared to be different from that described for intestinal epithelium.