Adrenal (SUPRARENAL) gland

Location: perirenal fat at the superior poles of the kidney.

CORTEX

Origin: mesodermal mesenchyme.

Function: steroid-secreting portion of gland that constitutes nearly 90% of the gland by weight.

Composition: thick connective tissue capsule from which trabeculae extend into the parenchyma.

Zona glomeruloza adrenocorticocytes, the outer zone that constitutes 15% of the cortical volume.

Function: Mineralocorticoids regulate sodium and potassium homeostasis and water balance. Aldosteron controls the blood pressure.

Zona fasciculata adrenocorticocytes, a thick middle zone that constitutes near 80% of the cortical volume.

Function: Glucocorticoids (95% activity in hydrocortisone) regulate glucose and fatty acid metabolism, provide resistance to stress, and suppress inflammatory response and some allergic reactions.

Zona reticularis adrenocorticocytes, the inner zone that constitutes only 5-7% of the cortical volume.

Function: Sex steroids - weak androgens.

MEDULLA

Origin: Neural crest cells that migrate into the developing gland.

Function: Catecholamine-secreting portion of the gland. They possess the sympathomimetic functions: increase heart rate, increase blood pressure, reduce blood flow to viscera and skin, stimulate conversion of glycogen to glucose, increase sweating, induce dilation of bronchioles, increase rate of respiration, decrease digestion, decrease urine production.

Composition: connective tissue with numerous sinusoidal blood capillaries and

Chromaffin cells, clusters of modified neurons.

Function: secretion of epinephrine, norepinephrine, and chromogranins.