ABSTRACT
The adrenal or suprarenal glands are located near the superior poles of the normally placed kidneys and contain two distinct different functioning areas of tissue, the cortex and the medulla. Although anatomically very close, the cortex and the medulla arise from two different and distinct areas. The adrenal medulla is derived from migrating ectodermal neural crest cells. The cortex develops from the primitive mesoderm medial to the urogenital ridge, starting about the 4th gestational week. By the 6th week, the cortex is apparent as an aggregation of mesenchyme on either side of the root of the mesentery and the developing gonad. At this time, nerve fibers, which the developing medullary cells will traverse, penetrate the developing adrenal cortex. The cortex develops two distinct areas by the 8th gestational week. The central area or the fetal zone is laterally and centrally located, while a thin rind develops on the outer aspect of the adrenal as the ultimate definitive adult cortex. The definitive cortex begins to differentiate into hormoneproducing zones, the zona glomerulosa and the zona
fasciculata, late in gestation. Most of the developing proliferation during the latter part of gestation is in the peripheral cortex region. The zona reticularis does not become apparent until about the end of the 3rd year of life (Figure 14.1). The zona glomerulosa or outermost layer of the definitive cortex will produce aldosterone. The zona fasciculata and zona reticularis will form a unit after the reticularis develops in early childhood. The zona fasciculata will produce the glucocorticoid hormones, while the zonal reticularis will produce the sex or androgen hormones.
