Circumventricular organ is

Circumventricular organ-Any of the structures in or near the base of the brain that differ from normal brain tissue in having capillaries that lack the usual blood-brain barrier and thus are not isolated from ceain compounds in the blood. The secretory organs include the subcommissural organ (SCO), the posterior pituitary, the pineal gland, the median eminence and the intermediate lobe of the pituitary gland. These organs are responsible for secreting hormones and glycoproteins into the peripheral vascular system using feedback from both the brain environment and external stimuli.Ref: Ganong&;s review of medical physiology; 24th edition; page no:-605