Adrenal cortex
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2008-05-10T21:34:26Z
194.82.51.28
{{Infobox Anatomy |
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Latin = cortex glandulae suprarenalis |
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Caption = Layers of cortex. |
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Precursor = [[mesoderm]]<ref name="titleEmbryology of the adrenal gland">{{cite web |url=http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=endocrin.box.466 |title=Embryology of the adrenal gland |accessdate=2007-12-11 |format= |work=}}</ref> |
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DorlandsPre = c_57 |
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[[Image:Adrenal gland (cortex).JPG|thumb|200px|Cortical part of the adrenal gland (on the pointer).]]
Situated along the perimeter of the [[adrenal gland]], the '''adrenal cortex''' mediates the stress response through the production of [[mineralocorticoid]]s and [[glucocorticoid]]s, including [[aldosterone]] and [[cortisol]] respectively. It is also a secondary site of [[androgen]] synthesis.
==Layers==<!-- This section is linked from [[Reticular layer]] -->
The cortex can be divided into three distinct layers of [[biological tissue|tissue]] based on their organisation. A useful mnemonic, GFR, relates to the glomerular filtration rate, as used in [[Glomerular filtration rate|clinical practice]].
{| class="wikitable"
| '''Layer''' || '''Name''' || '''Primary product'''
|-
| Most superficial cortical layer || [[zona glomerulosa]] || [[mineralocorticoid]]s (eg, [[aldosterone]])
|-
| Middle cortical layer || [[zona fasciculata]] || [[glucocorticoid]]s (eg, [[cortisol]])
|-
| Deepest cortical layer || [[zona reticularis]] || weak [[androgen]]s (eg, [[dehydroepiandrosterone]])
|}
==Steps of hormone synthesis==
* All adrenocortical hormones are synthesised from [[cholesterol]].
* [[Cholesterol]] is transported into the [[inner mitochondrial membrane]] by [[steroidogenic acute regulatory protein]] ({{Gene|STAR}}), where it is converted into [[pregnenolone]] by the enzyme {{Gene|CYP11A1}}. Accordingly, production of hormones in all three layers of the adrenal cortex is limited by the transportation of cholesterol into the [[mitochondria]] and by its conversion into pregnenolone.
* Pregnenolone can be either [[dehydrogenated]] to [[progesterone]], or [[hydroxylated]] to [[17-alpha-hydroxypregnenolone]].
The steps up to this point occur in many [[steroid]]-producing tissues. Subsequent steps, however, only occur in the adrenal cortex:
* Progesterone → (hydroxylation at C21) → [[Deoxycorticosterone]] → (two further hydroxylations) → [[Aldosterone]]
* Progesterone → (hydroxylation at C17) → 17-alpha-hydroxyprogesterone → (hydroxylation) → [[Deoxycortisol]] → (hydroxylation) → [[Cortisol]]
==Production==
The adrenal cortex produces a number of different [[corticosteroid]] [[hormone]]s:
*[[Mineralocorticoids]]: They are produced in the [[zona glomerulosa]]. The primary [[mineralocorticoid]] is [[aldosterone]]. Its secretion is regulated by the [[oligopeptide]] [[angiotensin II]] (angiotensin II is regulated by [[angiotensin I]], which in turn is regulated by [[renin]]). Aldosterone is secreted in response to high [[extracellular]] [[potassium]] levels, low extracellular [[sodium]] levels, and low fluid levels and blood volume. Aldosterone affects [[metabolism]] in different ways:
**It increases [[urine|urinary]] excretion of potassium [[ions]]
**It increases interstitial levels of sodium ions
**It increases water retention and blood volume
*[[Glucocorticoids]]: They are produced in the [[zona fasciculata]]. The primary glucocorticoid released by the adrenal gland is [[cortisol]]. Its secretion is regulated by the hormone [[Adrenocorticotropic hormone|ACTH]] from the [[anterior pituitary]]. Upon binding to its target, cortisol enhances [[metabolism]] in several ways:
**It stimulates the release of [[amino acid]]s from the body
**It stimulates [[lipolysis]], the breakdown of [[fat]]
**It stimulates [[gluconeogenesis]], the production of [[glucose]] from newly-released amino acids and [[lipid]]s
**It increases blood glucose levels in response to stress, by inhibiting glucose uptake into [[muscle cells|muscle]] and [[adipose tissue|fat cells]]
**It strengthens [[cardiac muscle]] contractions
**It increases water retention
**It has anti-inflammatory and anti-allergic effects
*[[Androgens]]: They are produced in the [[zona reticularis]]. The most important androgens include:
**[[Testosterone]]: a hormone with a wide variety of effects, ranging from enhancing muscle mass and stimulation of [[cell growth]] to the development of the [[secondary sex characteristic]]s.
**[[Dihydrotestosterone]] (DHT): a [[metabolism|metabolite]] of testosterone, and a more potent androgen than testosterone in that it binds more strongly to androgen receptors.
**[[Androstenedione]] (Andro): an androgenic steroid produced by the [[testes]], adrenal cortex, and [[ovaries]]. While [[androstenedione]]s are converted metabolically to testosterone and other [[androgen]]s, they are also the parent structure of [[estrone]].
**[[Dehydroepiandrosterone]] (DHEA): a steroid hormone produced from [[cholesterol]]. It is the primary precursor of natural [[estrogen]]s. DHEA is also called [[dehydroisoandrosterone]] or [[dehydroandrosterone]].
==Pathology==
* [[Adrenal insufficiency]] (e.g. due to [[Addison's disease]])
* [[Cushing's syndrome]]
* [[Congenital adrenal hyperplasia]]
* [[Conn's syndrome]]
==See also==
* [[Adrenal gland]]
==References==
{{Refimprove|date=December 2007}}
{{reflist}}
==External links==
* {{SUNYAnatomyLabs|40|04|02|03}} - "Posterior Abdominal Wall: Blood Supply to the Suprarenal Glands"
* {{MedicalMnemonics|180|2201|412|}}
* {{BUHistology|14502loa}}
* {{AnatomyAtlasesMicroscopic|15|292}} - "Adrenal Gland"
* [http://www.rahulgladwin.com/blog/2007/02/functions-of-adrenal-cortex.html Adrenal Cortex Medical Notes on rahulgladwin.com]
{{Adrenal gland}}
[[Category:Glands]]
[[Category:Abdomen]]
[[Category:Endocrine system]]
[[de:Nebenniere#Nebennierenrinde]]
[[pl:Kora nadnerczy]]
[[pt:Córtex adrenal]]