It distributes twigs to the adjacent muscles, and numerous branches to the thyroid gland, connecting with its fellow of the opposite side, and with the inferior thyroid arteries. The branches to the gland are generally two in number. One, the larger, supplies principally the anterior surface; on the isthmus of the gland it connects with the corresponding artery of the opposite side. A second branch descends on the posterior surface of the gland and anastomoses with the inferior thyroid artery.
Besides the arteries distributed to the muscles and to the thyroid gland, the branches of the superior thyroid are:
The infrahyoid branch (or hyoid artery): a small artery that runs along the lower border of the hyoid bone beneath the thyrohyoid muscle. This artery connects with the infrahyoid branch of the opposite side. The infrahyoid branch is a derivative of the secondaortic arch.
The cricothyroid artery may contribute to the supply of the larynx. It follows a variable course either superficial or deep to the sternothyroid muscle. If superficial, it may be accompanied by branches of the ansa cervicalis, and if deep, it may be related to the external laryngeal nerve. It can connect with the artery of the opposite side and with the laryngeal arteries.
Clinical significance
This artery must be ligated at the thyroid when conducting a thyroidectomy. If the artery is severed, but not ligated, it will bleed profusely. In order to gain control of the bleeding, the surgeon may need to extend the original incision laterally to ligate the artery at its origin at the external carotid artery. Furthermore, the external laryngeal branch of the superior laryngeal nerve courses close to the superior thyroid artery, making it at risk of injury during surgery.
