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Gland, in animals, organ that secretes essential substances. Endocrine glands (thyroid, adrenals, and pituitary) secrete hormones into the bloodstream. Exocrine glands secrete substances (perspiration, tears, mucus, saliva) via ducts into internal organs or onto body surfaces.

See also: Hormone.

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21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Ghibellines to Grand Prix