POSTNATAL-DEVELOPMENT OF ALIMENTARY CANAL IN OPOSSUM .1. ESOPHAGUS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 122  (NOV) , 293-314
Abstract
Ninety opossums (Didelphis virginiana) were used to examine the postnatal development of the esophagus. Pouch-young were divided into 10 groups according to their snout-rump lengths. Four adults were also used in the study. Tissues were studied by light microscopy and scanning and transmission electron microscopy. A quantitative estimate was made of the changes in the thickness of the epithelium and of the mitotic activity of the epithelium and subepithelial layers. The esophageal epithelium of the newborn opossum was 2-3 cells in depth. Ciliated cells and occasional goblet cells were observed by the 2.5 cm stage within the epithelium and in subsequent stages. The epithelium of the 4.5 cm opossum showed 3 distinct strata: a germinal layer, a spinous layer and, adjacent to the lumen, a flattened layer of cells that retained their nuclei. The epithelium throughout the postnatal period and in the adult did not undergo complete keratinization. The esophageal glands began as outgrowths from the epithelium just prior to 4.5 cm (about 20 days postnatal). The glands continued their development throughout the postnatal period. Secretory units of the esophageal glands were composed of 2 distinct cell types: a mucous form and a light, rounded cell type which was less numerous and occupied the terminal portions of the secretory units. The secretory product of the esophageal glands appeared complex, consisting of neutral and acid glycoproteins. Both cell types were encompassed by myoepithelial cells. The relationship of the mitotic sequences to the observations made by microscopic examination of the developing esophagus was discussed.