Median eminence
Template:Distinguish Template:Infobox brain The median eminence is generally defined as the portion of the ventral hypothalamus from which the portal vessels arise.<ref>Template:Cite book</ref> The median eminence is a small swelling on the tuber cinereum, posterior to and on top of the pituitary stalk; it lies in the area roughly bounded on its posterolateral region by the cerebral peduncles, and on its anterolateral region by the optic chiasm.
As one of the seven areas of the brain devoid of a blood–brain barrier,<ref name="windows">Template:Cite journal</ref> the median eminence is a circumventricular organ having permeable capillaries.<ref name="pmid3651843">Template:Cite journal</ref><ref name="gross1">Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Its main function is as a gateway for release of hypothalamic hormones,<ref name="palkovits">Template:Cite journal</ref> although it does share contiguous perivascular spaces with the adjacent hypothalamic arcuate nucleus, indicating a potential sensory role.<ref name=gross1/><ref name="shaver">Template:Cite journal</ref>
PhysiologyEdit
The median eminence is a part of the hypothalamus from which regulatory hormones are released.<ref name=windows/><ref name=palkovits/> It is integral to the hypophyseal portal system, which connects the hypothalamus with the pituitary gland. The pars nervosa (part of the posterior pituitary gland) is continuous with the median eminence via the infundibular stalk. Parvocellular neurosecretory cells from the hypothalamus terminate in the median eminence.<ref>Template:Cite book</ref>
The median eminence is the structure where secretions of the hypothalamus (releasing and inhibiting hormones) regulatory hormones, known as "hypophysiotropic hormones") collect before entering the portal system emptying into the general circulation.<ref name=windows/><ref name=palkovits/> Such hypophysiotropic hormones include: CRF (corticotropin-releasing factor), GnRH (gonadotropin-releasing hormone), TRH (thyrotropin-releasing hormone), GHRH (growth hormone-releasing hormone), and DA (dopamine).<ref name=palkovits/> These hypophysiotropic hormones stimulate or inhibit the release of hormones from the anterior pituitary.<ref name=palkovits/> Further, anatomical evidence exists for bidirectional communication between the median eminence and the arcuate and ventromedial nucleus of the hypothalamus.<ref name=gross1/><ref name=shaver/>