pineal gland

noun

variants or less commonly pineal or pineal body or pineal organ

: a small, typically cone-shaped structure of the brain that arises from the roof of the third ventricle, is enclosed by the pia mater, and functions primarily as an endocrine gland secreting melatonin

Note: The pineal gland varies in morphological complexity, and in some nonmammalian vertebrates (such as various reptiles) may serve a photoreceptive function.

Examples of pineal gland in a Sentence

Recent Examples on the Web

Melatonin is a hormone produced in the pineal gland that regulates the sleep-wake cycle and is an antioxidant.18 Melatonin supplements are taken by some people for sleep problems and jet lag. —Heather Jones, Verywell Health, 1 Aug. 2024

Melatonin is a hormone produced in the brain’s pineal gland that helps maintain our circadian rhythm—the 24-hour internal clock that regulates our sleep/wake cycles. —Margaret Osborne, Smithsonian Magazine, 18 Dec. 2023

Part of the problem, said Khan, is the disruption of production of melatonin, a naturally occurring hormone that is secreted by the pineal gland in response to darkness. —Cara Lynn Shultz, Peoplemag, 28 Aug. 2023

Secreted by the pineal gland, its presence in sufficient amounts is vital for the maintenance of a healthy sleep wake cycle. —Amber Smith, Discover Magazine, 14 Aug. 2023

Word History

First Known Use

1712, in the meaning defined above

Kids Definition

pineal gland

noun

pi·​ne·​al gland

ˈpī-nē-əl,

pī-ˈnē-

: a small usually cone-shaped part of the brain of most vertebrates that has an eyelike structure in reptiles and produces melatonin especially in response to darkness

called also pineal body

Medical Definition

pineal gland

noun

: a small body that arises from the roof of the third ventricle and is enclosed by the pia mater and that functions primarily as an endocrine gland that produces melatonin

called also pineal, pineal body, pineal organ