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Adrenal gland
	Endocrine system
	Adrenal gland
Latin	glandula suprarenalis
Gray's	subject #277 1278
System	Endocrine
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	Adrenal gland

In mammals, the adrenal glands (also known as suprarenal glands) are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position (ad-, "near" or "at" + renes, "kidneys"; and as concerns supra-, meaning "above"). They are chiefly responsible for releasing hormones in conjunction with stress through the synthesis of corticosteroids and catecholamines, including cortisol and adrenaline (epinephrine), respectively.

[edit] Anatomy and function

Anatomically, the adrenal glands are located in the thoracic abdomen situated 'on' top of the kidneys one on each side, specifically on their anterosuperior aspect. They are also surrounded by the adipose capsule and the renal fascia. In humans, the adrenal glands are found at the level of the 12th thoracic vertebra and receive their blood supply from the adrenal arteries. The adrenal gland is separated into two distinct structures, both of which receive regulatory input from the nervous system:

[edit] Adrenal cortex

The adrenal cortex is devoted to the synthesis of corticosteroid hormones from cholesterol. Some cells belong to the hypothalamic-pituitary-adrenal axis and are the source of cortisol and corticosterone synthesis. Under normal unstressed conditions, the human adrenal glands produce the equivalent of 35–40 mg of cortisone acetate per day.^[1] Other cortical cells produce androgens such as testosterone, while some regulate water and electrolyte concentrations by secreting aldosterone. In contrast to the direct innervation of the medulla, the cortex is regulated by neuroendocrine hormones secreted by the pituitary gland and hypothalamus, as well as by the renin-angiotensin system.

The cortex is divided into three zones, or layers. This division is sometimes referred to as "functional zonation". Moving from the outermost layer in:

[edit] Zona glomerulosa

The zona glomerulosa is the main site for production of mineralocorticoids, namely aldosterone, which plays an important role in the body's sodium homeostasis.

[edit] Zona fasciculata

The zona fasciculata is responsible for producing glucocorticoids, chiefly cortisol in humans. Cortisol secretion is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, by binding to a cell surface receptor and in turn increasing intracellular cAMP. In the absence of ACTH, the zona fasciculata secretes a basal level of cortisol.

[edit] Zona reticularis

The zona reticularis produces androgens, mainly dehydroepiandrosterone (DHEA) and DHEA sulfate in humans.

[edit] Adrenal medulla

The adrenal medulla is the core of the adrenal gland, and is surrounded by the adrenal cortex. The chromaffin cells of the medulla are the body's main source of the circulating catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). These water-soluble hormones, derived from the amino acid tyrosine, are part of the fight-or-flight response initiated by the sympathetic nervous system. The adrenal medulla can be considered as specialized ganglion of the sympathetic nervous system, lacking distinct synapses, instead releasing secretions directly into the blood.

[edit] Arteries and veins

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:

The superior suprarenal artery is provided by the inferior phrenic
The middle suprarenal artery is provided by the abdominal aorta
The inferior suprarenal artery is provided by the renal artery

Venous drainage of the adrenal glands is achieved via the suprarenal veins:

The right suprarenal vein drains into the inferior vena cava
The left suprarenal vein drains into the left renal vein or the left inferior phrenic vein.

The suprarenal veins may form anastomoses with the inferior phrenic veins.

The adrenal glands and the thyroid gland are the organs that have the greatest blood supply per gram of tissue. Up to 60 arterioles may enter each adrenal gland.^[2]

[edit] The adrenal gland in other animals

The adrenal gland is also found in non-mammals and serves much the same purposes. In teleost fish like trout, the gland forms part of the head kidney.^[3] There, adrenal cells are embedded in the resident lymphoid tissue. In cartilaginous fish like sharks, the adrenal gland is found within the posterior or main kidney.

[edit] See also

[edit] References

^ Jefferies, William (2004). Safe uses of cortisol. Charles C. Thomas Publisher. http://books.google.com/books?id=T6JLAgAACAAJ.
^ JE Skandalakis. Surgical Anatomy: The Embryologic And Anatomic Basis Of Modern Surgery (2004).
^ Adrenal Toxicology in Fishes, A Hontela, MM Vijayan. In: Adrenal Toxicology, Ed. by PW Harvey, D Everett, C Springall. Informa HealthCare, 2008, p. 235

[edit] External links

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

[safeuses-0] Jefferies, William (2004). Safe uses of cortisol. Charles C. Thomas Publisher. http://books.google.com/books?id=T6JLAgAACAAJ.

[1] JE Skandalakis. Surgical Anatomy: The Embryologic And Anatomic Basis Of Modern Surgery (2004).

[2] Adrenal Toxicology in Fishes, A Hontela, MM Vijayan. In: Adrenal Toxicology, Ed. by PW Harvey, D Everett, C Springall. Informa HealthCare, 2008, p. 235

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