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Importing Wikidata short description: "Posterior lobe of the pituitary gland" (Shortdesc helper) |
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{{Infobox anatomy
| Name = Posterior pituitary
| Latin =
| Greek =
| Image = File:Pituitary gland representation.PNG
| Caption = Pituitary gland. Posterior pituitary is in blue and Anterior pituitary is in orange. Pars nervosa and infundibular stalk are not labeled, but pars nervosa is at bottom and infundibular stalk is at top.
| Width =
| Image2 = File:Gray1181.png
| Caption2 = Median sagittal through the hypophysis of an adult monkey. (Posterior lobe labeled at bottom right.)
| Precursor = [[Neural tube]] (downward-growth of the [[diencephalon]])<ref>[http://www.med.unc.edu/embryo_images/unit-nervous/nerv_htms/nerv016a.htm Embryology at unc.edu]</ref>
| System =
| Artery = [[
| Vein = [[
| Nerve =
| Lymph =
}}
The '''posterior pituitary''' (or '''neurohypophysis''') is the [[Posterior (anatomy)|posterior]] lobe of the [[pituitary gland]] which is part of the [[endocrine system]]. The posterior pituitary is not glandular as is the [[anterior pituitary]]. Instead, it is largely a collection of [[axonal projection]]s from the [[hypothalamus]] that terminate behind the anterior pituitary, and serve as a site for the secretion of [[neurohypophysial hormone]]s ([[oxytocin]] and [[vasopressin]]) directly into the blood.<ref name="NHM-Neuroendocrine systems">{{cite book | vauthors = Malenka RC, Nestler EJ, Hyman SE | editor = Sydor A, Brown RY | title = Molecular Neuropharmacology: A Foundation for Clinical Neuroscience | year = 2009 | publisher = McGraw-Hill Medical | location = New York | isbn = 9780071481274 | pages = 246, 248–259 | edition = 2nd | chapter = Chapter 10: Neural and Neuroendocrine Control of the Internal Milieu | quote = <br />•The hypothalamic–neurohypophyseal system secretes two peptide hormones directly into the blood, vasopressin and oxytocin. ...<br />•The hypothalamic–pituitary–adrenal (HPA) axis. It comprises corticotropin-releasing factor (CRF), released by the hypothalamus; adrenocorticotropic hormone (ACTH), released by the anterior pituitary; and glucocorticoids, released by the adrenal cortex.<br />•The hypothalamic–pituitary–thyroid axis consists of hypothalamic thyrotropin-releasing hormone (TRH); the anterior pituitary hormone thyroid–stimulating hormone (TSH); and the thyroid hormones T<sub>3</sub> and T<sub>4</sub>.<br />•The hypothalamic–pituitary–gonadal axis comprises hypothalamic gonadotropin–releasing hormone (GnRH), the anterior pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the gonadal steroids.}}</ref> The '''hypothalamic–neurohypophyseal system'''<!--term redirects here, bolded per MOS:BOLD--> is composed of the hypothalamus (the [[paraventricular nucleus]] and [[supraoptic nucleus]]), posterior pituitary, and these axonal projections.<ref name="NHM-Neuroendocrine systems" />
==Structure==
The posterior pituitary consists mainly of [[neuron]]al projections ([[axon]]s) of [[magnocellular neurosecretory cell]]s extending from the [[supraoptic nucleus|supraoptic]] and [[paraventricular nucleus|paraventricular nuclei]] of the [[hypothalamus]]. These axons store and release neurohypophysial hormones [[oxytocin]] and [[vasopressin]] into the neurohypophyseal capillaries, from there they get into the [[systemic circulation]] (and partly back into the [[hypophyseal portal system]]). In addition to axons, the posterior pituitary also contains [[pituicyte]]s, specialized [[glial cell]]s resembling [[astrocyte]]s assisting in the storage and release of the hormones.<ref>{{cite journal|last=Hatton|first=GI|title=Pituicytes, glia and control of terminal secretion.|journal=The Journal of Experimental Biology|date=September 1988|volume=139|pages=67–79|doi=10.1242/jeb.139.1.67|pmid=3062122|url=http://jeb.biologists.org/content/139/1/67.full.pdf}}</ref>
Classification of the posterior pituitary varies, but most sources include the two regions below:
===Pars nervosa===
;Infundibular stalk: Also known as the [[Pituitary stalk|infundibulum]] or pituitary stalk, the infundibular stalk bridges the hypothalamic and hypophyseal systems.▼
===Infundibular stalk===
{{main | Pituitary stalk}}
▲
The [[median eminence]] is only occasionally included as part of the posterior pituitary. Other sources specifically exclude it from the pituitary.<ref>{{MeshName|Median+eminence}}</ref>
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===Hormone secretion===
Two hormones are classically considered as being related to the posterior pituitary: oxytocin and vasopressin. These hormones are created in the hypothalamus and released in the posterior pituitary. After creation, they are stored in neurosecretory vesicles regrouped into [[Herring bodies]] before being secreted in the posterior pituitary via the bloodstream.
{| class="wikitable"
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|-
| [[Oxytocin]]
|
| OT, OXY
| [[Uterus]], [[mammary gland]]s
| [[Uterine contraction]]s; [[lactation]]
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|-
| [[Vasopressin]]
|
| VP, AVP, ADH
| [[Kidney]]s and [[arteriole]]s
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==See also==
{{Anatomy-terms}}
* [[Anterior pituitary]]
* [[Hypothalamic–pituitary–adrenal axis]]
* [[Hypothalamic–pituitary–thyroid axis]]
* [[Hypothalamic–pituitary–gonadal axis]]
==References==
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{{DEFAULTSORT:Posterior Pituitary}}
[[Category:Endocrine system anatomy]]
[[Category:Neuroendocrinology]]
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