Circumventricular organ in the context of "Vascular organ of lamina terminalis"

The area postrema, a paired structure in the medulla oblongata of the brainstem, is a circumventricular organ having permeable capillaries and sensory neurons that enable its role to detect circulating chemical messengers in the blood and transduce them into neural signals and networks. Its position adjacent to the bilateral nuclei of the solitary tract and role as a sensory transducer allow it to integrate blood-to-brain autonomic functions. Such roles of the area postrema include its detection of circulating hormones involved in vomiting, thirst, hunger, and blood pressure control.

The median eminence is generally defined as the portion of the ventral hypothalamus from which the portal vessels arise. 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, the median eminence is a circumventricular organ having permeable capillaries. Its main function is as a gateway for release of hypothalamic hormones, although it does share contiguous perivascular spaces with the adjacent hypothalamic arcuate nucleus, indicating a potential sensory role.