CorpusHuman Anatomy
EndocrineOrgan part

Pituitary stalk and median eminence

Infundibulum; eminentia mediana

Also known as: infundibulum, infundibular stalk, hypophyseal stalk, median eminence

The funnel-shaped connection between the hypothalamus and pituitary, carrying neurosecretory axons to the posterior lobe and the portal vessels that link the median eminence to the anterior lobe.

Show on body map Hypothalamic–Pituitary Axis

Overview

The median eminence is the swollen base of the tuber cinereum; it is a circumventricular organ with fenestrated capillaries, so it is the interface where hypothalamic hormones enter blood. Below it the infundibular stem descends through an opening in the diaphragma sellae to the posterior lobe, sheathed in front by the pars tuberalis of the anterior pituitary.

The stalk carries two parallel communication channels: (1) the hypothalamo-hypophyseal tract — ≈100 000 unmyelinated axons from the supraoptic and paraventricular nuclei carrying ADH and oxytocin to the posterior lobe; and (2) the long hypophyseal portal veins, which collect blood rich in releasing/inhibiting hormones from the primary capillary plexus of the median eminence and carry it to the secondary plexus (sinusoids) of the anterior lobe.

Location

Passes from the floor of the third ventricle through the diaphragma sellae into the sella turcica, posterior to the optic chiasm.

Parts & subdivisions

  1. Median eminence
    Primary capillary plexus (from the superior hypophyseal arteries) receiving releasing hormones; specialised ependymal cells called tanycytes line its ventricular surface.
  2. Infundibular stem
    Neural part of the stalk, continuous with the pars nervosa.
  3. Pars tuberalis
    Collar of adenohypophysial tissue around the stem; contains gonadotrophs and expresses melatonin receptors.
  4. Long portal veins
    Run along the stalk from the primary to the secondary plexus.

Anatomy

Arterial supply

Superior hypophyseal arteries (internal carotid) to the primary plexus of the median eminence and upper stalk.

Function

  • Conveys ADH and oxytocin along axons to the posterior pituitary.
  • Conveys hypothalamic releasing/inhibiting hormones to the anterior pituitary via portal blood.

Clinical significance

Stalk effect

Compression or transection (large adenoma, trauma, surgery) cuts dopamine delivery, so prolactin rises (usually to moderate levels, <≈2000–3000 mU/L) while other anterior pituitary hormones fall. A thickened stalk on MRI suggests hypophysitis, germinoma, sarcoidosis or histiocytosis.

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