The adrenal (or suprarenal) glands are paired endocrine glands situated over the medial aspect of the upper poles of each kidney

They are retroperitoneal, with parietal peritoneum covering their anterior surface only

The right gland is pyramidal in shape, contrasting with the semi-lunar shape of the left gland

Perinephric (or renal ) fascia encloses the adrenal glands and kidney

This fascia attaches the glands to the crura of the diaphragm

Each adrenal gland is composed of two distinct tissues, encapsulated by the connective tissue known as the capsule

Cortex

Medulla

Veins and lymphatics leave each gland via the hilum, but arteries and nerves enter the glands at numerous sites

Cortex and medulla are the functional portion of the gland

Is yellowish in colour

Functionally, it can be divided into three regions

Zona glomerulosa

Produces and secretes mineralocorticoids such as aldosterone

Zona fasciculata

Produces and secretes glucocorticoids such as cortisol. It also secretes a small amount of androgens

Zona reticularis

Produces and secretes androgens such as dehydroepiandrosterone. It also secretes a small amount of corticosteroids

Lies in the centre of the gland, and is dark brown in colour

It contain chromaffin cells, which are neuroendocrine cells that are modified sympathetic ganglia

They secrete catecholamines (epinephrine and norepinephrine) into the bloodstream in response to stress

These hormones produce a flight-or-fight response

Chromaffin cells also secrete enkephalins which function in pain control

Mineralocorticoids, mainly aldosterone – regulates blood pressure and electrolyte balance

Glucocorticoids, such as cortisol – increases blood sugar levels, suppresses the immune system, and aids in metabolism

Catecholamines – prepare the body for the fight-or-flight response by increasing the heart rate, constricting blood vessels, increasing the metabolic rate, heightening cognitive awareness, and increasing the respiratory rate

Arterial supply

Superior adrenal artery – arises from inferior phrenic artery

Middle adrenal artery – arises from abdominal aorta

Inferior adrenal artery – arises from the renal arteries

Venous drainage

Right and left adrenal veins

Right adrenal vein drains into the inferior vena cava

Left adrenal vein drains into the left renal vein