ultimobranchial gland, in biology, any of the small bodies in the pharynx that develop behind the fifth pair of gill pouches in the vertebrate embryo. In mammals the ultimobranchial tissue has become incorporated into the parafollicular cells of the thyroid gland. Ultimobranchial glands produce the hormone calcitonin, which reduces the amount of calcium in the blood.

This article was most recently revised and updated by Kara Rogers.
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