Posterior pituitary

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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.)
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	n_07/12569241

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

Contents 1 Anatomy 2 Major hormones secreted 3 Role in disease 4 References 5 Additional images

[edit] Anatomy

It 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. [3]
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.[4] Other sources specifically exclude it from the pituitary.[5]

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

[edit] 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	Target	Effect	Source
Oxytocin	Uterus, mammary glands	Uterine contractions; lactation	paraventricular nuclei
Vasopressin (antidiuretic hormone; ADH)	Kidneys or Arterioles	Stimulate water retention or raise blood pressure by contracting arterioles	supraoptic

[edit] 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.

[edit] References

1. ^ Embryology at unc.edu
2. ^ Dorlands/Elsevier l_13/12501193
3. ^ Histology at BU 14004loa
4. ^ Dorlands/Elsevier n_07/12569241
5. ^ MeSH Median+eminence

[edit] Additional images

The posterior pituitary comprises the posterior lobe of the pituitary gland.

Hypothalamic nuclei

v • d • e Brain: diencephalon
Epithalamus	Pineal body, Habenula, Habenular nuclei
Hypothalamus	anterior: Anterior hypothalamic nucleus, Paraventricular nucleus, Preoptic area, Supraoptic nucleus, Suprachiasmatic nucleus intermediate/middle/tuberal/pituitary: infundibulum, median eminence, arcuate nucleus, Ventromedial nucleus, Dorsomedial hypothalamic nucleus, Tuber cinereum, Pituitary gland (Anterior pituitary, Posterior pituitary) posterior/lateral: posterior nucleus, Mammillary body, Lateral nucleus
Subthalamus	Subthalamic nucleus, Zona incerta
Thalamus	Pulvinar, Metathalamus (Medial geniculate nucleus, Lateral geniculate nucleus), list of thalamic nuclei
Other	Third ventricle, Interventricular foramina, Optic chiasm, Subfornical organ