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Blood Supply of the Hypothalamus and Pituitary

المؤلف:  Wass, J. A. H., Arlt, W., & Semple, R. K. (Eds.).

المصدر:  Oxford Textbook of Endocrinology and Diabetes

الجزء والصفحة:  3rd edition , p113-114

2026-01-18

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 See Figure 1. The hypothalamus is supplied by small arteries which penetrate the base of the brain. These are derived from vessels forming the circle of Willis in the interpeduncular fossa. An anteromedial group from the anterior cerebral and anterior communicating arteries supply the anterior part of the hypothalamus including the optic chiasm, suprachiasmatic, and supraoptic regions and the anterior column of the fornix. A posteromedial group from the posterior communicating artery and proximal part of the posterior cerebral artery supply more posterior parts of the hypothalamus. Superior hypophyseal arteries usually arise from the internal carotid immediately after it pierces the sellar diaphragm. They form anterior and posterior branches and a plexus of vessels which sur round the infundibulum. From these some branches pass toward the ependyma of the third ventricle in the median eminence where they are surrounded by a plexus of capillaries (gomitoli). In the median eminence arteries give rise to fenestrated capillaries that form an external (mantle) plexus and an internal (deep) plexus. From the external and internal plexus, long portal vessels descend along the stalk to the anterior pituitary where they branch repeatedly to form the vascular sinusoids that surround the anterior pituitary endocrine cells. Short portal vessels formed from the capillary plexus lower in the stalk also pass to the anterior pituitary. There are no capillaries among the cells of the pars intermedia. The anterior pituitary therefore has no direct arterial supply, but its fenestrated sinusoids are fed entirely by the long and short portal vessels. By contrast, the posterior pituitary and the lower part of the pituitary stalk receives a direct arterial supply from the inferior hypophyseal arteries, derived from the internal carotid artery within the cavernous sinus, and which pass directly into the posterior pituitary to form a plexus of fenestrated capillaries within that gland. A few small branches from the artery pass forward and give some supply to the periphery of the anterior pituitary. Collecting veins draining all the parts of the pituitary pass via the intercavernous and cavernous sinuses into the inferior petrosal sinus and from there into the internal jugular vein. Inferior petrosal sinus blood sampling can therefore be useful in the diagnosis of pituitary tumours.

Fig1. Vasculature of the pituitary gland.

Whereas the capillaries in most of the hypothalamus are continuous and, with the surrounding astrocytic end feet, form an effective blood– brain barrier, those in the median eminence are fenestrated, The fenestrations of the median eminence capillaries not only allow those capillaries to collect the hypophysiotropic hormones secreted by the terminals of the parvocellular neurosecretory neurons and to transfer them to the anterior pituitary, but they also provide a route whereby otherwise impermeant peptide hormones secreted by fat (e.g. leptin), the pancreas (e.g. insulin) and the gut (e.g. ghrelin) can reach neurons in the arcuate nucleus around the base of the third ventricle, where they are important signals in the homeostatic control of feeding behaviour. The median eminence is therefore one of the ‘circumventricular organs’ of the third ventricle (c.f. the organum vasculosum of the lamina terminalis, subfornical organ, and area postrema) where the blood– brain barrier is permeable.