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Collection of cells or tissue that removes specific substances from the blood, alters or concentrates them, and then either releases them for further use by the body or eliminates them. Typically, the functional cells of a gland rest on a membrane and are surrounded by a meshwork of blood vessels. Endocrine, or ductless, glands (e.g., pituitary, thyroid, adrenal) discharge hormones into the bloodstream directly rather than through ducts (seeendocrine system). Exocrine glands (e.g., digestive, mammary, salivary, sweat) discharge their products through ducts.
This entry comes from Encyclopædia Britannica Concise. For the full entry on gland, visit Britannica.com.