The circumventricular organs

Charanjit Kaur and Eng-Ang Ling

Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore

Offprint requests to: Charanjit Kaur, Department of Anatomy, Yong Loo Lin School of Medicine, MD10, 4 Medical Drve, National University of Singapore, Singapore 117594. e-mail: antkaurc@nus.edu.sg

Summary. The circumventricular organs (CVOs) are midline structures located around the third and fourth ventricles that are characterized by a lack of blood-brain barrier. The pineal gland, median eminence, neuro-hypophysis and the subcommisural organ are classified as secretory, whereas the subfornical organ, area postrema and the organum vasculosum of the lamina terminalis as the sensory CVOs. Glial cells consisting of astrocytes and microglia/macrophages are present in all these organs. The pineal gland, neurohypophysis and the median eminence lack the presence of neurons that are present in the rest of the CVOs. Most of the CVOs are lined by ependymal cells except for the pineal and the neurohypophysis. Modified ependymal cells known as tanycytes are present in the ependymal lining. These organs are important sites for communication with the cerebrospinal fluid as well as between the brain and peripheral organs via blood-borne products as they lack the blood-brain barrier. Histol Histopathol 32, 879-892 (2017)

Key words: Pineal gland, Median eminence, Neurohypophysis, Subcommisural organ subfornical organ, Area postrema, Organum vasculosum of the lamina terminalis

DOI: 10.14670/HH-11-881