Adrenal glands (also known as suprarenal glands) are important endocrine glands of human body. They are two in number, one lying on the upper pole of each kidney. They are yellowish in color and are surrounded by renal fascia.
Each adrenal gland has an outer yellow cortex and inner brown medulla. Each of the right and left adrenal glands has different external structure.
Right adrenal gland:
The right adrenal gland is pyramid shaped and is present at the upper pole of right kidney.
It lies behind the right lobe of the liver and extends medially behind the inferior vena cava. Posteriorly, it rests on the diaphragm.
Left adrenal gland:
The left adrenal gland is crescentic in shape. It extends along the medial border of the left kidney from the upper pole to the hilus.
It lies behind the pancreas and the lesser sac of peritoneal cavity. It also rests on the posterior surface of the diaphragm.
Hormones of adrenal glands:
The adrenal glands secrete a variety of hormones. Hormones secreted by the cortex are different from those secreted by the medulla.
Hormones secreted by cortex:
The cortex of adrenal glands secretes three types of hormones: Mineral Corticoids, Gluco-corticoids and Sex hormones.
- Mineral corticoids: These are concerned with the control of fluid and electrolyte balance.
- Gluco-corticoids: These are concerned with the control of the metabolism of carbohydrates, fats, and proteins
- Sex hormones: Small amounts of sex hormones are released by the cortex. These hormones are concerned with pre-pubertal development of sex organs.
Hormones secreted by medulla:
The medulla secretes the catecholamines; epinephrine and norepinephrine.
Each gland receives arterial blood supply from three arteries:
- Inferior phrenic artery
- Suprarenal artery
- Renal artery
Venous blood from each gland is drained by a single vein, which emerges from the hilus. On the right side, the vein drains into inferior vena cava, whereas on the left, it drains into renal vein.
The lymph from both glands drains into the lateral aortic nodes.
Preganglionic sympathetic fibers derived from the splanchnic nerves supply the glands. Most of the nerves end in the medulla of the gland.