The superior thyroid artery arises from the external carotid artery just below the level of the greater cornu of the hyoid bone and ends in the thyroid gland.

Structure

From its origin under the anterior border of the sternocleidomastoid the superior thyroid artery runs upward and forward for a short distance in the

carotid triangle The carotid triangle (or superior carotid triangle) is a portion of the anterior triangle of the neck. Coverings and boundaries It is bounded: * Posteriorly by the anterior border of the Sternocleidomastoid; * Anteroinferiorly, by the superior bel ...

, where it is covered by the skin,

platysma The platysma muscle is a superficial muscle of the human neck that overlaps the sternocleidomastoid. It covers the anterior surface of the neck superficially. When it contracts, it produces a slight wrinkling of the neck, and a "bowstring" effec ...

, and fascia; it then arches downward beneath the omohyoid,

sternohyoid The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure The sternoh ...

, and sternothyroid muscles. To its medial side are the

inferior pharyngeal constrictor muscle The inferior pharyngeal constrictor muscle is a skeletal muscle of the neck. It is the thickest of the three outer pharyngeal muscles. It arises from the sides of the cricoid cartilage and the thyroid cartilage. It is supplied by the vagus nerve ...

and the external branch of the

superior laryngeal nerve The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of vagus nerve and in its course receives a branch from the superior cervical ganglion of the sympathetic nervous system. The superi ...

Branches

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 The inferior thyroid artery is an artery in the neck. It arises from the thyrocervical trunk and passes upward, in front of the vertebral artery and longus colli muscle. It then turns medially behind the carotid sheath and its contents, and als ...

. 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 The thyrohyoid muscle is a small skeletal muscle on the neck. It originates from the lamina of the thyroid cartilage, and inserts into the greater cornu of the hyoid bone. It is supplied by the hypoglossal nerve, and a branch of the ventral rami o ...

. This artery connects with the infrahyoid branch of the opposite side. The infrahyoid branch is a derivative of the second

aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...

. *The sternocleidomastoid branch runs downward and laterally across the sheath of the

common carotid artery In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
sternocleidomastoideus The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the access ...

muscle and neighboring muscles and skin; it frequently arises as a separate branch from the external carotid artery. * The superior laryngeal artery accompanies the

internal laryngeal branch The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of vagus nerve and in its course receives a branch from the superior cervical ganglion of the sympathetic nervous system. The supe ...

of the

, beneath the

. This artery branches from the superior thyroid artery near its bifurcation from the external carotid artery. Together with the

internal laryngeal nerve The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of vagus nerve and in its course receives a branch from the superior cervical ganglion of the sympathetic nervous system. The superi ...

, it pierces the lateral thyrohyoid membrane, and supplies blood to the muscles,

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...

, and glands of the larynx, connecting with the branch from the opposite side. *The cricothyroid artery may contribute to the supply of the larynx. It follows a variable course either superficial or deep to the

sternothyroid muscle The sternothyroid muscle, or sternothyroideus, is an infrahyoid muscle in the neck. It acts to depress the hyoid bone. It is below the sternohyoid muscle. It is shorter and wider than the sternohyoid. Structure The sternothyroid arises from the ...

. If superficial, it may be accompanied by branches of the

ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin. Bran ...

, 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 A thyroidectomy is an operation that involves the surgical removal of all or part of the thyroid gland. In general surgery, endocrine or head and neck surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other conditio ...

. 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 in close proximity to the superior thyroid artery, making it at risk for injury during surgery.

Additional images

File:Gray474.png, Diagram showing the origins of the main branches of the carotid arteries. File:Gray513.png, The internal carotid and vertebral arteries. Right side. (Superior thyroid visible at center.) File:Gray1174.png, The thyroid gland and its relations. File:Gray1210.png, Side of neck, showing chief surface markings. File:Slide3jjj.JPG, Superior thyroid artery File:Slide1EBAB.JPG, Muscles, arteries and nerves of neck.Newborn dissection. File:Slide2deded.JPG, Muscles, nerves and arteries of neck.Deep dissection. Anterior view.

References

External links