Contain chromaffin granules, precursors of epinephrine and norepinephrine. Richly supplied with blood. The adrenal cortex is essential for life, and, through its hormones, is involved in numerous body functions. These activities include the maintenance of water and electrolyte balance, carbohydrate metabolism, and the normal functioning of connective tissue cells. The adrenal medulla is not essential for life.
Medullary cells store their hormones in the form of granules.
During normal activity only a small amount of catecholamine is secreted, but this is greatly increased during stressful periods of intense emotional reaction. It is believed that epinephrine and norepinephrine are secreted by two different types of cells. The epinephrine secreting cells are primarily located around the distal ends of sinusoids draining the adrenal cortex, whereas norepinephrine-secreting cells are associated with capillaries of the direct arterial supply of the medulla. All adrenal medullary cells are innervated by cholinergic nerve terminals of preganglionic sympathetic neurons. Chromaffin cells are also found in paraganglia, which are collections of catecholamine-secreting cells associated with autonomic ganglia.