Dictionary Definition

neurohypophysis n : the posterior lobe of the pituitary body; primarily glandular in nature [syn: posterior pituitary, posterior pituitary gland, pars nervosa] [also: neurohypophyses (pl)]

User Contributed Dictionary

English

Noun

neurohypophysis (plural neurohypophyses)
  1. the posterior lobe of the pituitary gland, responsible for the release of oxytocin and Antidiuretic Hormone (ADH), also called vasopressin

Extensive Definition

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

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:
A few sources include the pars intermedia as part of the posterior lobe, but this is a minority view. It is based upon the gross anatomical separation of the posterior and anterior pituitary along the cystic remnants of Rathke's pouch, causing the pars intermedia to remain attached to the neurohypophysis.

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.

Role in disease

Insufficient secretion of vasopressin is central todiabetes 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

Additional images

Image:Nasennebenhöhlen.gif

See Also

neurohypophysis in German: Hypophysenhinterlappen
neurohypophysis in Spanish: Neurohipófisis
neurohypophysis in French: Neurohypophyse
neurohypophysis in Finnish: Neurohypofyysi
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