Inferior thyroid artery

At a glance

English

Inferior thyroid artery

Latin (TA2)

Arteria thyreoidea inferior arteria thyroidea inferior

System

Artery

Region

Neck

Side

Paired, left and right

About the inferior thyroid artery

The inferior thyroid artery is the main vessel to the lower half of the thyroid gland and the chief supply of the parathyroid glands. It arises low in the neck from the thyrocervical trunk, a short branch of the first part of the subclavian artery.

Its course is a characteristic loop. It first climbs along the medial border of scalenus anterior, anterior to longus colli and the vertebral artery. At about the level of the sixth cervical vertebra it bends medially and passes behind the carotid sheath, which holds the common carotid artery, internal jugular vein and vagus nerve, and deep to the sympathetic trunk, whose middle cervical ganglion often sits on the artery here. It then descends onto the back of the gland's lower pole and divides into upper and lower glandular branches.

Those glandular branches supply the posterior and lower parts of the gland and the parathyroids, and link with the superior thyroid artery as well as the opposite inferior thyroid artery. The vessel also gives the inferior laryngeal artery, which runs up with the recurrent laryngeal nerve beneath the inferior constrictor to the larynx and joins the superior laryngeal artery; tracheal branches that meet bronchial arteries below; oesophageal branches that meet oesophageal branches of the aorta; pharyngeal branches; and the ascending cervical artery, which climbs on the cervical transverse processes between scalenus anterior and longus capitis, feeding neck muscles and sending spinal branches through the intervertebral foramina.

In thyroid surgery the artery is a key landmark because the recurrent laryngeal nerve crosses close to it, usually behind but sometimes in front of or between its branches. Careless ligation can therefore cause hoarseness, and tying the trunk too close to the gland may deprive the parathyroids of blood and lead to low calcium after thyroidectomy. Surgeons often ligate only its branches on the gland surface for this reason.

Course and supply

Arises from

Arises from the thyrocervical trunk, a branch of the first part of the subclavian artery.

Ends in

Ends at the thyroid's lower pole in glandular branches that join the superior thyroid artery and its fellow of the other side; it also gives inferior laryngeal, tracheal, oesophageal, pharyngeal and ascending cervical branches.

Supplies

Supplies the lower and posterior thyroid, the parathyroid glands, the larynx below the vocal folds, the trachea, oesophagus and pharynx, and, through the ascending cervical artery, deep neck muscles and the cervical spinal canal.