pineal gland

epiphysis, small endocrine gland which is located in the center of the brain and secretes the hormone melatonin (Anatomy)

The pineal gland (also called the pineal body, epiphysis cerebri, or epiphysis) is a small endocrine gland in the brain. It is shaped like a tiny pine cone, and is located near the center of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join. It produces melatonin, a hormone that may weakly modulate wake/sleep patterns.
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Noun
1. a small endocrine gland in the brain; situated beneath the back part of the corpus callosum; secretes melatonin
(synonym) pineal body, epiphysis cerebri, epiphysis
(hypernym) endocrine gland, endocrine, ductless gland

A small gland located in the brain.

[PIN-ee-al]
A tiny organ in the cerebrum that produces melatonin. Also called pineal body or pineal organ.