The omohyoid is a digastric muscle with two bellies and an intermediate tendon, running from the scapula around a fascial pulley on the clavicle to the hyoid bone. Its unusual two-belly anatomy with a fascial sling around the intermediate tendon allows it to change direction of pull, making it both a hyoid depressor and a fascial tensor. Surgeons encounter it as a landmark in the posterior cervical triangle and anterior neck.
| Origin | Superior border of the scapula medial to the suprascapular notch |
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| Insertion | Lower border of the hyoid bone via two bellies connected by an intermediate tendon held by a fascial sling to the clavicle |
| Nerve Supply | Ansa cervicalis (C1, C2, C3) |
| Blood Supply | Superior thyroid artery; Transverse cervical and suprascapular arteries (inferior belly) |
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By tensing the deep cervical fascia it reduces venous pressure in the jugular vein during inspiration, preventing the vein from collapsing and maintaining venous return. This fascial tensioning role is unique among the infrahyoid muscles.
The omohyoid is a key landmark in neck surgery. Its superior belly divides the anterior triangle into the carotid and muscular triangles, and its inferior belly divides the posterior triangle into the occipital and supraclavicular triangles. Where it crosses the internal jugular vein, roughly at the level of the cricoid cartilage, it marks the surgical boundary between level III and level IV lymph nodes in neck dissection, and it is often divided at its intermediate tendon to expose the deep structures. Omohyoid syndrome, a rare condition in which the muscle bulges or snaps over its fascial sling, produces a visible and palpable lateral neck mass with swallowing or neck movement that can be mistaken for a lymph node or vascular lesion.
The posterior belly of the omohyoid is palpable crossing the posterior triangle of the neck between the sternocleidomastoid and trapezius muscles, and the anterior belly can be felt during swallowing adjacent to the thyroid cartilage.
Rare snapping of the intermediate tendon over its fascial sling producing a visible neck mass with head turning that resolves spontaneously or rarely requires surgical excision.
