pineal gland

variants: or less commonly pineal or pineal body or pineal organ

Definition of pineal gland

: 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 The hormone is secreted throughout the night by the pineal gland in the center of the brain, inducing and maintaining drowsiness. Claudia Wallis, Scientific American, 18 Nov. 2017 The episode’s title comes from the antiviral treatment, which is created by combining hybrid bone-marrow stem cells with secretions from the pineal gland of a living hybrid. Oliver Sava, Vulture, 5 June 2021 Melatonin is secreted by the pineal gland, located deep within the brain, and released into the bloodstream. Sandee Lamotte, CNN, 22 Mar. 2021 That turns out to be significant, since synchronic messes with the pineal gland—hence its unusual effects with regard to how users experience time. Jennifer Ouellette, Ars Technica, 22 Nov. 2020 Deep within the brain lies a pea-sized gland called the pineal gland, which primarily produces the hormone melatonin. Miriam Fauzia, USA TODAY, 24 Nov. 2020 Because of his cancer, Steve has the uncalcified pineal gland of a teenager rather than an adult. Jennifer Ouellette, Ars Technica, 22 Nov. 2020 Infrared thermometers, which are held near the forehead to scan body temperature without direct contact, point an infrared light directly at the brain's pineal gland, exposing it to harmful radiation. Beatrice Dupuy, Star Tribune, 31 July 2020 It is produced in the pea-size pineal gland, which is nestled in the middle of your brain and syncs melatonin production with the rising and setting of the sun. Anna Goldfarb, New York Times, 24 Apr. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'pineal gland.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of pineal gland

1712, in the meaning defined above

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The first known use of pineal gland was in 1712

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Dictionary Entries Near pineal gland

pineal eye

pineal gland

pine aphid

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Cite this Entry

“Pineal gland.” Dictionary, Merriam-Webster, Accessed 25 Oct. 2021.

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More Definitions for pineal gland

pineal gland


Medical Definition of pineal gland

: 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

More from Merriam-Webster on pineal gland Encyclopedia article about pineal gland


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