circumventricular organ

Introduction

A group of specialized structures within the brain, so named because the occupy strategic positions along the ventricles.

Characteristics

features which characterize circumventricular organs:

• ependymal cells
  • tend not to be cuboidal as are most ependymal cells
  • have tight junctions
  • supra-ependymal cells are often observed at the ventricular surface
• highly vascularized structures
• fenestrated endothelium with loss of the blood-brain barrier (except for subcommissural organ)
  • the blood-CSF barrier is provided by tight junctions between ependymal cells

Function

• these organs function as chemoreceptor zones (CR) or neurohumoral organs (NH).

Structure

circumventricular organs include:

• subfornical organ
• vascular organ of the lamina terminalis (CR)
• median eminence (NH)
• posterior pituitary gland (NH)
• pineal gland
• subcommissural organ (NH)
• area postrema (CR)
• choroid plexus

More general terms

• central nervous system structure

More specific terms

• area postrema
• choroid plexus
• median eminence of hypothalamus
• organum vasculosum lamina terminalis (OVLT)
• pineal gland (body)
• posterior pituitary (neurohypophysis)
• subcommissural organ
• subfornical organ

Additional terms

• blood-brain barrier; blood-CSF barrier; plasma-CSF barrier