Adrenal_glands are located above each kidney (ad = above; renal = kidney). The adrenal glands are divided into two regions: (1) the cortex and (2) the medulla. The cortex is the upper layer of the gland and is capped by a CT capsule. The medulla is the inner layer of the gland. The micrograph shows a central vein in the medulla, which is called the medullary_vein.

The medulla develops from neural tissue and is controlled by the sympathetic_nervous_system, or SNS. The medullary cells respond to stress by producing epinephrine and norepinephrine to elicit the "fight-or-flight" response. Old names for epinephrine and norepinephrine are adrenaline and noradrenaline.

The cortex is divided into three layers, or zones:

(1) zona_glomerulosa,

(2) zona_fasciculata, and

(3) zona_reticularis

The layers of the cortex collectively produce steroid hormones known as corticosteroids. The corticosteroids are divided into three groups:

(1) Mineralocorticoids, such as aldosterone, which are produced in the zona glomerulosa; the

(2) Glucocorticoids, such as the cortisones, which are produced in the zona fasciculata; and the

(3) Gonadocorticoids, such as the estrogens, progesterone, and testosterones, which are produced in the zona reticularis, along with some glucocorticoids.