ultimobranchial bodies
embryonic derivatives of the fourth pharyngeal pouches (sometimes described as a rudimentary fifth pouch); they migrate along with the parathyroid glands and are incorporated in the thyroid gland. In vertebrates other than mammals, these remain as discrete masses in the neck or mediastinum throughout adult life. The parafollicular cells of these bodies produce calcitonin. Called also postbranchial or telobranchial b's.
Medical dictionary.
2011.