[TA] a transitory endodermal tube in the embryo, carrying thyroid-forming tissue at its caudal end; normally, the duct disappears after the thyroid has moved to its definitive location in the neck; its point of origin is regularly marked on the root of the adult tongue by the foramen cecum; occasionally, its incomplete regression results in the formation of cysts along its embryonic course.pyramidal lobe of thyroid gland. SYN: ductus thyroglossus [TA], thyrolingual duct.