Omohyoid muscle

Omohyoid muscle is a two-bellied infrahyoid muscle situated in the anterior and lateral neck. It extends from the scapula to the hyoid bone.

Anatomical details

1. Origin

The inferior belly originates from the superior border of the scapula, near the suprascapular notch.

2. Insertion

The superior belly inserts into the inferior border of the body of hyoid bone, lateral to the insertion of sternohyoid muscle.

Connection

The two bellies are united by an intermediate tendon, which is anchored to the clavicle and first rib by a fascial sling derived from the deep cervical fascia.

Innervation

The omohyoid muscle is innervated by branches from the anterior rami of C1 to C3 spinal nerves, which form the ansa cervicalis.

• The ansa cervicalis is a nerve loop derived from the cervical plexus (C1–C3) that lies on the anterior surface of the carotid sheath. It supplies motor innervation to most infrahyoid muscles, including the sternohyoid, sternothyroid, and omohyoid..

Action

Depresses, retracts, and steadies the hyoid bone during swallowing and speech.

Relations

• Inferior belly lies in the posterior triangle of the neck, crossing the lower part of the internal jugular vein.

• Superior belly lies in the anterior triangle, deep to the sternocleidomastoid and sternohyoid muscles.