The Adrenal Cortex Consists of Three Distinct Zones

In the adult human, the adrenal cortex consists of three his-tologically distinct zones or layers (Fig. 34.1). The outer zone, which lies immediately under the capsule of the gland, is called the zona glomerulosa and consists of small clumps of cells that produce the mineralocorticoid aldosterone. The zona fasciculata is the middle and thickest layer of the cortex and consists of cords of cells oriented radial to the center of the gland. The inner layer is comprised of interlaced strands of cells called the zona reticularis. The zona fasciculata and zona reticularis both produce the physiologically important glucocorticoids, cortisol and corticosterone. These layers of the cortex also produce the

The Three Zones The Adrenal Cortex
The three zones of the adrenal cortex and corresponding hormone secretion.

androgen dehydroepiandrosterone, which is related chemically to the male sex hormone testosterone. The molecular structures of these hormones are shown in Figure 34.2.

Like all endocrine organs, the adrenal cortex is highly vascularized. Many small arteries branch from the aorta and renal arteries and enter the cortex. These vessels give rise to capillaries that course radially through the cortex and terminate in venous sinuses in the zona reticularis and adrenal medulla,- therefore, the hormones produced by the cells of the cortex have ready access to the circulation.

The cells of the adrenal cortex contain abundant lipid droplets. This stored lipid is functionally significant because cholesterol esters present in the droplets are an important source of the cholesterol used as a precursor for the synthesis of steroid hormones.

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