DEVELOPMENT OF THE FETAL ADRENALS IN NONHUMAN PRIMATES: ELECTRON MICROSCOPY ,

Abstract

Publisher Summary This chapter discusses the development of the fetal adrenals in nonhuman primates. The adrenal gland of the human fetus largely comprises a unique region, termed the fetal zone, that occupies the majority of the cortex during fetal life and regresses soon after birth. Similar temporary fetal zones have been noted in armadillos, lions, mice, and rats. The initial subdivision of the human adrenal cortex into an inner fetal zone and an outer definitive zone occurs during the first trimester. Each zone arises from a separate proliferation of coelomic epithelium. The first aggregation of epithelium occurs in week 4 when the cortex becomes a distinct entity. Between months 2 and 3, a rudimentary permanent cortex appears as a thin peripheral rim of epithelium on the surface of the preexisting cellular mass. The outer zone comprises cells with the characteristics of rapidly dividing stem cells. The scanty cytoplasm contains free ribosomes; small, dense mitochondria with a few lamelliform cristae; and not much lipid.