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Adrenai Cland: Histology

ENDOCRINE PHYSIOLOGY

Capsule Zona glomerulosa

Capsular plexus

Capsule

Cortical capillaries Fasciculata

Medullary capillaries

Normal human suprarenal gland

Humań suprarenal gland after administration of crude ACTH

Schemalic stereogram of intrinsic suprarenal circulation

Suprarenal artery (one of many)

Figurę 8.12 Adrenal Gland Histology-

The adrenal gland consiSlS of a cortex and medulla, and both regions are richly vascularized by a radially oriented plexus of ves5els. The adrenal cortex produces morę than two dozen steroid hormones and sfrucfurally is divided into three distinct hislological regions: an miler zona glomerulosa that produces mineralocorticoids {princi-paUy aldosterone), a mtddle zona fasciculata that produces glucocor-ócoids (primarily cortisol. corticosterone, and cortisone), and an -nner zona rełicularis that produces androgens. As shown in this fig-ACTH stimulation significantly affects the mainlenance and func •>on of the inner two layers of the adrenal cortex. The adrenal medulla occupies the center of the adrenal gland and produces epi-nepbrine and norepinophrine. The medullary < dis ar.tually are the postganglionic elements of the sympathetic division of the autonomie nervous system, but as endocrine cells, they rclcasc epineph-rine and norepinephrine into the blood rather than into a synaptic cleft. Epinephrine accounts for about 70% to 80% of fhe medullary secretions. As illustrated in the lower panel, blood drains trom the cortex into the medulla. This vascular arrangement enstires that the medulla receives large amounts of cortisol, which stimulates the enzyme that converts norepinephrine to epinephnne (i.e., phcnylethanolamine-N-methyłtransferasef.

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