Thyroid Grafts

Abstract

During the fifth week of gestation, the thyroglossal anlage arises from the ventral wall of the primitive pharynx at the foramen cecum and migrates caudally. The thyroid gland arises from proliferation of the cells at the distal end of this diverticulum. The thyroglossal duct usually disappears, but if it persists it may become enveloped in the developing hyoid bone. During this same period of development, the ultimobranchial bodies arise from the fourth branchial arch. They migrate laterally around the neck to fuse with the developing thyroid gland. This is all that is known about the ultimobranchial bodies. There is no evidence that they are actually thyrogenic. An aberrant thyroid gland is the development in an abnormal site of the body's total thyroid tissue. An accessory thyroid gland is a supplementary fraction of thyroid tissue that grows at a distance from a normally placed gland. Aberrant or accessory thyroid glands may