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circumventricular organ
A group of specialized structures within the brain, so named because the occupy strategic positions along the ventricles.
Function:
- these organs function as chemoreceptor zones (CR) or neurohumoral organs (NH).
Structure:
circumventricular organs include:
1) subfornical organ
2) vascular organ of the lamina terminalis (CR)
3) median eminence (NH)
4) posterior pituitary gland (NH)
5) pineal gland
6) subcommissural organ (NH)
7) area postrema (CR)
8) choroid plexus
Characteristics:
features which characterize circumventricular organs:
1) ependymal cells
a) tend not to be cuboidal as are most ependymal cells
b) have tight junctions
c) supra-ependymal cells are often observed at the ventricular surface
2) highly vascularized structures
3) 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
Related
blood-brain barrier; blood-CSF barrier; plasma-CSF barrier
Specific
area postrema
choroid plexus
median eminence of hypothalamus
organum vasculosum lamina terminalis (OVLT)
pineal gland (body)
posterior pituitary (neurohypophysis)
subcommissural organ
subfornical organ
General
central nervous system structure
References
- The Human Nervous System, George Paxinos,
Academic Press, San Diego CA 1990
- Stedman's Medical Dictionary 27th ed, Williams &
Wilkins, Baltimore, 1999