Adrenal gland

Adrenal gland
Endocrine system
Adrenal gland
Latin	glandula suprarenalis
Gray's	subject #277 1278
Artery	superior suprarenal artery, middle suprarenal artery, Inferior suprarenal artery
Vein	suprarenal veins
Nerve	celiac plexus, renal plexus
Lymph	lumbar glands
MeSH	Adrenal+Glands
Dorlands/Elsevier	g_06/12392729

The adrenal glands (also known as suprarenal glands) are the triangle-shaped endocrine glands that sit atop the kidneys; their name indicates that position (ad, "near" or "at" + renes, "kidneys"). They are chiefly responsible for regulating the stress response through the synthesis of corticosteroids and catecholamines, including cortisol and adrenaline.

Overview

Anatomically, the adrenal glands are located in the abdomen, situated on the anteriosuperior aspect of the kidneys. In humans, the adrenal glands are found at the level of the 12th thoracic vertebra and receive their blood supply from the adrenal arteries.

It is separated into two distinct structures, both of which receive regulatory input from the nervous system.

• As its name suggests, the adrenal medulla is at the center of the adrenal gland surrounded by the adrenal cortex. The adrenal medulla is the body's main source of the catecholamine hormones adrenaline (epinephrine) and noradrenaline (norepinephrine).

• By contrast, some cells of the adrenal cortex belong to the hypothalamic-pituitary-adrenal axis and are the source of cortisol synthesis. Other cortical cells produce androgens such as testosterone, while some regulate water and electrolyte concentrations by secreting aldosterone.

Blood supply

Although variations of the blood supply to the adrenal glands (and indeed the kidneys themselves) are common, there are usually three arteries that supply each adrenal gland:

Artery	Source
superior suprarenal artery	inferior phrenic
middle suprarenal artery	abdominal aorta
Inferior suprarenal artery	renal artery

Hormones

The adrenal glands secrete steroids, including some sex hormones, and catecholamines. Steroids are synthesized and secreted by the adrenal cortex, while catecholamines are synthesized and secreted by chromaffin cells of the adrenal medulla.

• The principal steroids are aldosterone (a mineralocorticoid) and cortisol (a glucocorticoid).
  • Aldosterone promotes sodium retention and potassium excretion and is therefore important in maintaining fluid balance and blood pressure.
  • Cortisol on the other hand has a wide range of metabolic effects such as protein and fat breakdown that aim to elevate of blood glucose levels.

• Many sex hormones are secreted including testosterone and oestrogen. The sex hormone that is secreted by the adrenals that has the most influence is dehydroepiandrosterone (DHEA). It has virilising effects and is important in development and maintenance of pubic hair, axillary hair, pubertal growth spurts, and sex drive. The effects are only significant in females as the effects are masked by high testosterone levels in males.

• Catecholamines that the adrenal glands secrete are adrenaline and noradrenaline. Adrenaline has the more influential effects. The affects of adrenaline and noradrenaline are wide ranging; adrenaline has a more marked effect on the heart and metabolic activities while noradrenaline is involved more in peripheral vasoconstriction. Adrenaline and noradrenaline secretion is stimulated directly by sympathetic neurons in response to stressors.

The adrenal glands secrete other hormones as well.

Additional images

Abdominal portion of the sympathetic trunk, with the celiac and hypogastric plexuses.	Posterior abdominal wall.	Suprarenal glands viewed from the front.	Suprarenal glands viewed from behind.
	Above each human kidney is one of the two adrenal glands.

See also

• Fight-or-flight response
• Stress

References

• MedlinePlus Encyclopedia 002219
• Virtual Slidebox at Univ. Iowa Slide 272
• Anatomy Atlases - Microscopic Anatomy, plate 15.292 - "Adrenal Gland"
• Histology at BU 14501loa
• SUNY Labs 40:03-0105 - "Posterior Abdominal Wall: The Retroperitoneal Fat and Suprarenal Glands"
• Adrenal Gland, from Colorado State University
• Cross section at UV pembody/body8a

Endocrine system - Adrenal glands
Medulla: Chromaffin cells Cortex: Zona glomerulosa | Zona fasciculata | Zona reticularis