Suprarenal gland

At a glance

English

Suprarenal gland

Latin (TA2)

Glandula suprarenalis

System

Endocrine gland

Region

Abdomen

Side

Paired, left and right

About the suprarenal gland

The suprarenal (adrenal) glands are paired, yellowish endocrine organs lying behind the peritoneum on the upper and medial aspect of each kidney, at about the level of the eleventh and twelfth ribs. Each is roughly five centimetres high, three wide and up to a centimetre thick, and the pair together weigh under ten grams. They lie inside the renal fascia with the kidneys but in a separate compartment, divided from them by a thin septum and cushioned by perirenal fat, so a kidney can be removed or can drop without taking the gland with it.

The two differ in shape and relations. The right gland is pyramidal and sits higher; it lies behind the inferior vena cava and the bare area of the liver, with the right crus of the diaphragm behind it. The left is crescent-shaped and slightly larger, draped along the medial border of the kidney above the hilum; the stomach, the body of the pancreas and the splenic artery lie in front of it, and the left crus behind. A furrow on the front of each gland, the hilum, is where its main vein leaves.

In section each gland has a thick outer cortex and a thin, darker inner medulla, which are really two different organs. The cortex, derived from mesoderm, has three zones. The outer zona glomerulosa makes aldosterone, which helps the kidney keep sodium and so controls blood pressure; the zona fasciculata makes cortisol, which mobilises fuel and damps inflammation and immunity; and the inner zona reticularis makes weak androgens. The medulla comes from neural crest and acts as a modified sympathetic ganglion: its chromaffin cells release adrenaline and noradrenaline directly into the blood in response to stress.

Disorders reflect these products. Too much cortisol causes Cushing syndrome, and too much aldosterone causes primary aldosteronism with high blood pressure and low potassium. Failure of the cortex, as in Addison disease, brings weakness, low blood pressure and skin darkening and can lead to a life-threatening crisis. Congenital adrenal hyperplasia is an inherited fault in steroid synthesis. Tumours of the medulla (phaeochromocytomas) cause bouts of high blood pressure, and small incidental lumps are often found on scans done for other reasons.

Function and supply

Function

The cortex secretes aldosterone, cortisol and weak androgens; the medulla releases adrenaline and noradrenaline into the blood during stress.

Nerve supply

Preganglionic sympathetic fibres, chiefly from the greater splanchnic nerve via the coeliac and suprarenal plexuses, end directly on the medullary cells; the cortex is controlled mainly by hormones (ACTH and the renin-angiotensin system).

Blood supply

Superior suprarenal arteries from the inferior phrenic artery, a middle suprarenal artery from the aorta and inferior suprarenal arteries from the renal artery; a single suprarenal vein drains the right gland into the inferior vena cava and the left into the left renal vein.