The superior thyroid artery arises from the

external carotid artery The external carotid artery is a major artery of the head and neck. It arises from the common carotid artery when it splits into the external and internal carotid artery. External carotid artery supplies blood to the face and neck. Structure T ...

just below the level of the greater cornu of the

hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical verteb ...

and ends in the

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

Structure

From its origin under the anterior border of the

sternocleidomastoid 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 ...

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 A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal organs ...

; it then arches downward beneath the

omohyoid The omohyoid muscle is a muscle that depresses the hyoid. It is located in the front of the neck, and consists of two bellies separated by an intermediate tendon. The omohyoid muscle is proximally attached to the scapula and distally attached to t ...

, sternohyoid, and

sternothyroid 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 ...

muscles. To its medial side are the inferior pharyngeal constrictor muscle 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

, connecting with its fellow of the opposite side, and with the

inferior thyroid arteries 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 ...

. 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

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 The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ea ...

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

. * The superior laryngeal artery accompanies the internal laryngeal branch of the

, beneath the

. This artery branches from the superior thyroid artery near its bifurcation from the

. 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 The larynx (), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...

, 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. Bra ...

, 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 In modern medicine, a surgeon is a medical professional who performs surgery. Although there are different traditions in different times and places, a modern surgeon usually is also a licensed physician or received the same medical training as ...

may need to extend the original incision laterally to ligate the artery at its origin at the

. 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