Viscera of the neck

Abstract

The thyroid gland is a symmetrical H-shaped endocrine structure in the lower neck. It consists of two lobes, each extending from the oblique line of the thyroid cartilage above to the sixth tracheal ring below – united by a median isthmus covered by the anterior jugular veins. The small, (usually) paired and inconsistent parathyroid glands lie behind the lobes of the thyroid gland. They measure 6mm by 4mm by 2mm and are ordinarily four in number – two superior and two inferior. They are involved in the careful regulation of the body’s calcium levels. Both superior and inferior glands are ordinarily supplied by the inferior thyroid artery. Drainage is into the venous plexus on the anterior surface of the thyroid.