<prompt> Not a circumventricular organ ?Subfornical areaNeurohypophysisAdenophysisOVLT  <response>: Ans. is c i.e., Adenophysis Structures outside the blood brain barrierCeain areas of brain have fenestrated capillaries and because of their permeability, are said to be outside blood-brain barrier. These areas are located around the third ventricle and are therefore called circumventricular organs. These areas are i Posterior pituitary neurohypophysis and the adjacent ventral pa of median eminence of the hypothalamus; ii The area postrema; iii The organ vasculusum of lamina terminalis OVLT; and iv Subfornical organs SFO.Although the blood-brain barrier is deficient in the circumventricular organs, the blood-CSF barrier in these organs is quite effective due to the presence of tight-junctions between the modified ependymal cells of the third ventricle called the tancytes. 