The sternothyroid is a strap muscle connecting the sternum directly to the thyroid cartilage, depressing the larynx after it has been elevated during swallowing. It is deeper than the sternohyoid and lies directly on the thyroid gland, making it a landmark structure in thyroid surgery. The oblique line of the thyroid cartilage, its insertion, is also where the thyrohyoid and inferior pharyngeal constrictor attach.
| Origin | Posterior surface of the manubrium sterni below the origin of the sternohyoid |
|---|---|
| Insertion | Oblique line on the lamina of the thyroid cartilage |
| Nerve Supply | Ansa cervicalis (C1, C2, C3) |
| Blood Supply | Superior thyroid artery |
| Actions | Depresses the thyroid cartilage and larynx after swallowing; Resists upward displacement of the larynx during the swallowing sequence |
|---|
After the larynx is elevated by the suprahyoid muscles during swallowing to protect the airway, the sternothyroid and other infrahyoid muscles return it to its resting position, restoring normal breathing after each swallow.
The sternothyroid and sternohyoid strap muscles are routinely divided during thyroid and parathyroid surgery and reapproximated at closure without significant functional consequence, as the ansa cervicalis provides their nerve supply from a distal direction that does not require reattachment. Post-thyroidectomy dysphagia is usually from cricothyroid muscle scarring rather than strap muscle denervation.
The sternothyroid is palpable deep to the sternohyoid in the midline neck between the thyroid cartilage notch and the manubrium during swallowing.
Strap muscle strain from blunt anterior neck trauma producing dysphagia and voice changes from disrupted laryngeal descent mechanics.
