Pineal Body

pineal gland

 or pineal body

Endocrine gland in the brain that produces melatonin. It is large in children and begins to shrink at puberty. The gland may play a significant role in sexual maturation, circadian rhythm and sleep induction, and seasonal affective disorder and depression. In animals it is known to play a major role in sexual development, hibernation, and seasonal breeding.

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pineal body [′pin·ē·əl ‚bäd·ē]

(anatomy)

An unpaired, elongated, club-shaped, knoblike or threadlike organ attached by a stalk to the roof of the vertebrate forebrain. Also known as conarium; epiphysis.

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Pineal Body 

(also called pineal eye), an eyelike organ in some higher fishes, such as dipnoans and some holosteans, and in such reptiles as the tuatara and many lizards. It develops from an outgrowth of the roof of the diencephalon and communicates with the diencephalon by means of an unpaired nerve. The structure of the pineal body is particularly similar to that of the ordinary paired eye in reptiles: their pineal body has a crystalline lens that faces the parietal foramen in the roof of the skull and that has a multilayered retina with photosensitive and pigmentary cells. The pineal body in some lizards perceives differences in light. The pineal body is reduced in higher vertebrates.