POSTERIOR_PITUITARY

(Redirected from Neurohypophysis)

The 'posterior pituitary' (or 'neurohypophysis') comprises the posterior lobe of the pituitary gland and is part of the endocrine system.

Contents

Anatomy

Major hormones secreted

Role in disease

References

Additional images

Anatomy

The 'Posterior Pituitary Gland' consists mainly of neuronal projections (axons) extending from the supraoptic and paraventricular nuclei of the hypothalamus that secrete peptide hormones into the capillaries of the hypophyseal circulation.
The neurohypophysis also contains a specialised type of astrocytic glial cell - "pituicytes".
Despite its name, the posterior pituitary gland is not a gland, ''per se''; rather, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary gland.
Classification of the posterior pituitary varies, but most sources include the three regions below:

'Region'	'Description'
pars nervosa, or neural lobe, or posterior lobe[2]	This region consistutes the majority of the posterior pituitary, and is sometimes (incorrectly) considered synonymous with it. Notable features include Herring bodies and pituicytes. [2]
infundibular stalk	Also known as the "infundibulum" or "pituitary stalk". The term "hypothalamic-hypophyseal tract" is a near-synonym, describing the connection rather than the structure.
median eminence	This is only occasionally included as part of the posterior pituitary.[2] Other sources specifically exclude it from the pituitary.[2]

A few sources include the pars intermedia as part of the posterior lobe, but this is a minority view.

Major hormones secreted

Hormones known classically as posterior pituitary hormones are synthesized by the hypothalamus. They are then stored and secreted by the posterior pituitary into the bloodstream.

Hormone	Other names	Symbol(s)	Target	Effect	Source
Oxytocin	-	-	Uterus, mammary glands	Uterine contractions; lactation	paraventricular nuclei
Vasopressin	Arginine vasopressin, argipressin, antidiuretic hormone	AVP, ADH	Kidneys or Arterioles	Stimulates water retention; raises blood pressure by contracting arterioles	supraoptic

Role in disease

''Insufficient secretion'' of vasopressin is central diabetes insipidus, in which the body loses the capacity to concentrate urine. Affected individuals excrete as much as 20 L of dilute urine per day.
''Oversecretion'' of vasopressin causes the syndrome of inappropriate antidiuretic hormone.

References

1. Embryology at unc.edu
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Additional images