CorpusHuman Anatomy
EndocrineOrgan part

Posterior pituitary (neurohypophysis)

Neurohypophysis; lobus posterior hypophysis

Also known as: neurohypophysis, pars nervosa

The neural lobe of the pituitary, made of axon terminals of hypothalamic neurons, which stores and releases antidiuretic hormone and oxytocin directly into the blood.

Show on body map Hypothalamic–Pituitary Axis

Overview

The neurohypophysis is not a gland in the usual sense: it synthesises no hormones. It consists of the unmyelinated axons of supraoptic and paraventricular magnocellular neurons (the hypothalamo-hypophyseal tract), their terminals on fenestrated capillaries, and supporting glial cells called pituicytes. Hormone-filled neurosecretory granules accumulate in axonal dilatations called Herring bodies.

When the parent neurons fire, action potentials reach the terminals, Ca²⁺ enters and granules release ADH or oxytocin together with their neurophysin into the capillaries of the inferior hypophyseal arteries. Because release is neural, responses are rapid (seconds), e.g. ADH within minutes of a rise in osmolality and oxytocin within a minute of suckling.

Location

Posterior part of the sella turcica, behind the anterior lobe; continuous above with the infundibular stem.

Parts & subdivisions

  1. Pars nervosa
    Main body of the lobe containing axon terminals, Herring bodies and pituicytes.
  2. Infundibular stem
    Neural stalk carrying the axons.

Anatomy

Arterial supply

Inferior hypophyseal arteries (cavernous internal carotid); drains to the cavernous sinus, with short portal vessels to the anterior lobe.

Histology

Unmyelinated axons, Herring bodies (eosinophilic granule-filled dilatations), pituicytes (astrocyte-like glia) and fenestrated capillaries.

Function

  • Releases ADH (water reabsorption, vasoconstriction).
  • Releases oxytocin (uterine contraction, milk ejection).

Clinical significance

Posterior pituitary bright spot

Stored hormone–neurophysin granules make the normal posterior lobe hyperintense on T1-weighted MRI; loss of this bright spot supports central diabetes insipidus.

Ectopic posterior pituitary

In congenital hypopituitarism the bright spot may lie at the median eminence with a thin or absent stalk (pituitary stalk interruption syndrome).

Compiled from standard anatomy and physiology references — see the Endocrine System sources. For education only; not medical advice.