Histogenesis of the Proventricular Submucosal Gland of the Chick as Revealed by Light and Electron Microscopy

Author Institution: Malone College, Canton, OhioThe development of the submucosal tubuloalveolar glands of the proventriculus was studied with both light and electron microscopes, with special reference given to the 13-18-day period. Beginning as an invagination in the stratified columnar epithelium lining the lumen of the proventriculus, the simple tubular gland, by repeated bifurcation of the invaginated portion, by sloughing of the superficial cells, and by remodeling of the residual basal cells from columnar to cuboidal, becomes a compound tubuloalveolar gland composed of numerous secretory units. Concomitant with the gross cellular changes, ultrastructural changes in the intercellular membranes are evident. By day 4 after hatching, the cells forming the secretory units appear to be functional