| Posterior pituitary | |
|---|---|
| Pituitary gland. Posterior pituitary is in blue. Pars nervosa and infundibular stalk are not labeled, but pars nervosa is at bottom and infundibular stalk is at top.) | |
| Median sagittal through the hypophysis of an adult monkey. (Posterior lobe labeled at bottom right.) | |
| Latin | glandula pituitaria, pars nervosa |
| Gray's | subject #275 1275 |
| Artery | inferior hypophyseal artery |
| Vein | hypophyseal vein |
| Precursor | Neural tube (downward-growth of the diencephalon)[1] |
| MeSH | Pituitary+Gland,+Posterior |
| Dorlands/Elsevier | Posterior pituitary hormones |
The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system. 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.
Contents |
The posterior pituitary consists mainly of neuronal projections (axons) extending from the supraoptic and paraventricular nuclei of the hypothalamus. These axons release peptide hormones into the capillaries of the hypophyseal circulation. In addition to axons, the posterior pituitary also contains pituicytes, specialized glial cells resembling astrocytes.
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.
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 | - | OT | Uterus, mammary glands | Uterine contractions; lactation | supraoptic and paraventricular nuclei |
| Vasopressin (antidiuretic hormone) | Arginine vasopressin, argipressin, antidiuretic hormone | VP, AVP, ADH | Kidneys or Arterioles | Stimulates water retention; raises blood pressure by contracting arterioles, induces male aggression | supraoptic and paraventricular nuclei |
Insufficient secretion of vasopressin underlies diabetes insipidus, a condition in which the body loses the capacity to concentrate urine. Affected individuals excrete as much as 20 liters of dilute urine per day. Oversecretion of vasopressin causes the syndrome of inappropriate antidiuretic hormone (SIADH).
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