Sternohyoid muscle

The sternohyoid muscle is a bilaterally paired, long, thin, narrow strap muscle of the anterior neck. It is one of the infrahyoid muscles. It is innervated by the ansa cervicalis. It acts to depress the hyoid bone.

The sternohyoid muscle is a flat muscle located on both sides of the neck, part of the infrahyoid muscle group. It originates from the medial edge of the clavicle, sternoclavicular ligament, and posterior side of the manubrium, and ascends to attach to the body of the hyoid bone. The sternohyoid muscle, along with other infrahyoid muscles, functions to depress the hyoid bone, which is important for activities such as speaking, chewing, and swallowing. Additionally, this muscle group contributes to the protection of the trachea, esophagus, blood vessels, and thyroid gland. The sternohyoid muscle also plays a minor role in head movements.

Structure
The sternohyoid muscle is one of the paired strap muscles of the infrahyoid muscles.

The muscle is directed superomedially from its origin to its insertion. The two muscles are separated by a considerable interval inferiorly, but usually converge by their mid-point and remain proximal until their superior insertion.

Origin
It arises from the posterior aspect of the medial end (sternal extremity of the clavicle, the posterior sternoclavicular ligament, and (the superoposterior portion of) the manubrium of sternum.

It inserts onto the inferior border of the body of hyoid bone.

Nerve supply
The sternohyoid muscle receives motor innervation from branches of the ansa cervicalis (which are ultimately derived from cervical spinal nerves C1-C3).

Relations
The muscle is situated lateral to the trachea.

Variations
The muscle may be absent, doubled, exhibit a clavicular slip (the cleidohyoideus), or interrupted by a tendinous intersection; it sometimes presents a transverse tendinous inscription just distal to its origin.

Actions/movements
The muscle depresses the hyoid bone when the bone is in an elevated position.

Function
The sternohyoid muscle performs a number of functions:


 * aids in speech (it is primarily involved in modulation with speech volume rather than intonation ).
 * contributes to movements of the head and neck.