Adrenal

The adrenal glands are small glands located in the retroperitoneal space immediately above the kidneys (ad meaning above and renal meaning kidneys). Comprised of an outer cortex and inner medulla layer, the adrenal glands produce a variety of hormones that are essential to maintaining the normal function of the body.

The adrenal cortex, or outer portion of the adrenal gland has three layers, each producing a unique hormone:

1. zona glomerulosa, the outermost layer, produces aldosterone
2. zona fasciculata, the middle layer, produces the steroid cortisol
3. zona reticularis, the inner layer, also contributes to cortisol production

The adrenal medulla, or inner portion of the adrenal gland, produces a group of hormones collectively referred to as catecholamines, including the hormones epinephrine and norepinephrine. These hormones are essential to the 'fight and flight' function of the nervous system and are better known as adrenaline.

The adrenal glands have a rich arterial blood supply arising from small vessels from the phrenic and renal arteries as well as from the aorta. The right adrenal gland has a single vein that drains directly into the inferior vena cava whereas the left adrenal vein drains directly into the left renal vein. On the left side, the inferior phrenic vein often joins the adrenal vein.