Omohyoid muscle

At a glance

English

Omohyoid muscle

Latin (TA2)

Musculus omohyoideus

System

Muscle

Region

Neck

Side

Paired, left and right

About the omohyoid muscle

Omohyoid is a long, narrow infrahyoid muscle with two bellies joined by a short tendon. Its name links the shoulder (Greek omos) to the hyoid. It lies on the side and front of the neck and is the most lateral of the strap muscles below the hyoid, outside sternohyoid and on the surface of sternothyroid and thyrohyoid.

The inferior belly begins on the scapula's upper edge close to the scapular notch, and sometimes on the ligament that bridges the notch. It runs forwards and slightly upwards across the lower neck, is tied down near the clavicle by a fibrous band, and passes behind sternocleidomastoid. There it becomes the intermediate tendon, which a sling of deep cervical fascia anchors to the clavicle and the first rib; this sling gives the muscle its angled shape. The superior belly then climbs almost vertically beside sternohyoid to end on the hyoid body's lower edge, just lateral to sternohyoid.

Omohyoid pulls the hyoid downwards and backwards after it has been raised in swallowing or speaking, and helps keep it steady so that the suprahyoid muscles can act from it. Some think its pull on the fascia also keeps the internal jugular vein open during deep breathing. It is supplied by the ansa cervicalis from the cervical plexus: the superior belly by its superior root, carrying C1 fibres, and the inferior belly by the loop itself, carrying C1 to C3. Its blood comes from the superior thyroid and transverse cervical or suprascapular arteries.

The muscle is an important landmark. Its inferior belly divides the posterior triangle into an upper occipital part and a lower supraclavicular part, and its superior belly splits the anterior triangle into the carotid triangle above and the muscular triangle below. Its intermediate tendon lies over the internal jugular vein and guides surgeons to the vein during neck dissection. It may be doubled, missing, or arise from the clavicle instead of the scapula.

Attachments, action and supply

Origin

The scapula's upper edge near the scapular notch (inferior belly).

Insertion

Lower edge of the hyoid body, lateral to sternohyoid (superior belly).

Action

Depresses and steadies the hyoid bone after swallowing and speaking.

Nerve supply

Ansa cervicalis (C1 to C3).

Blood supply

Superior thyroid and transverse cervical or suprascapular arteries.