Posterior pituitary

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

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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.

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 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
2. ^ l_13/12501193 at Dorland's Medical Dictionary
3. ^ Histology at BU 14004loa
4. ^ n_07/12569241 at Dorland's Medical Dictionary
5. ^ MeSH Median+eminence

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