Not a circumventricular organ ?

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'.