Sternohyoid muscle

Origin and insertion

Sternohyoid muscle originates from the upper posterior aspect of manubrium of sternum and the posterior surface of the medial end of clavicle .

It extends superomedially and inserts to the inferior border of body of hyoid bone, where it adjoins the insertion of the contralateral sternohyoid muscle.

Relations

Same as other three infrahyoid muscles, the sternohyoid muscle is contained within the muscular triangle of the neck, a subdivision of the anterior triangle. The superior part of the muscle lies very close to its contralateral fellow while below the middle of their course, there is a considerable gap between them.

It lies posteriorly to the platysma and anteriorly to the larynx, the thymus (or thymic remnants) and the thyrohyoid and sternothyroid muscles. The sternohyoid (together with the sternothyroid, separates the anterior jugular vein (superficially) from the common carotid artery (deeply).

Learn more about the infrahyoid and other muscles of the anterior neck here.

Innervation

Sternohyoid muscle is innervated by ansa cervicalis, a loop formed by the anterior rami of spinal nerves C1-C3 within the cervical plexus.

Blood supply

Vascular supply to sternohyoid comes from the superior thyroid artery (a branch of the external carotid artery), while the venous blood is conveyed by the superior thyroid vein.

Function

The action of the sternohyoid muscle is to depress the hyoid bone after it has been elevated by the suprahyoid muscles. The elevation of the hyoid bone and thus the larynx, happens during swallowing. This action closes the airways, preventing the food from being inhaled.

Once the food pass from the pharynx to esophagus, the sternohyoid muscle aids to reopening the laryngeal inlet by depressing the hyoid bone and larynx, thus reinstating the breathing process.