The pineal body in mammals is a small organ which is an ovoid evagination of the diencephalon at the posterior corner of the third ventricle. The pineal body contains pinealocytes, which are endocrine in nature, and numerous glial cells. The organ is heavily innervated by sympathetic fibers. It is developed throughout the vertebrate classes, but in fish, amphibia, and reptiles it is characteristically associated with the parietal eye, which contains photosensitive cells behind a primitive lens. In these animals, the pinealocytes in the pineal body are also photosensitive. Both organs, the parietal eye and pineal body, which are connected by a nervous stem, are collectively called the pineal complex.
KeywordsPineal Gland Outer Segment Superior Cervical Ganglion Lower Vertebrate Pineal Organ
Unable to display preview. Download preview PDF.