Classic Endocrine Glands

Abstract

An epithelial lined vesicle results from Rathke’s pouch by the tenth day of gestation in Didelphis and lies in close association with the presumptive infundibulum of the diencephalon. At this stage of development, the newly formed multichambered pituitary vesicle is of uniform thickness. The epithelial wall of the pituitary vesicle consists of spindle-shaped cells and is pseudostratified in appearance. The dorsal wall remains uniformly thin and as development continues will form the pars intermedia. In contrast, the ventral wall of the pituitary vesicle thickens due to a proliferation of cells from within this layer and ultimately gives rise to cells of the pars distalis. Just prior to birth, the lumen of the multichambered pituitary vesicle becomes reduced to a flattened, curved cleft but continues to clearly delineate the pars intermedia from the forming pars distalis (Sherman and Krause 1990). By the end of the second postnatal week the relationships between the pars distalis, pituitary cleft, pars intermedia and pars nervosa are well established, and few changes other than size are observed during the remainder of pituitary development (Wheeler 1943).