Omohyoid (Inferior Belly)

Origin, Insertion, Action & Nerve

Attachments explained

The Omohyoid (Inferior Belly) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Action & function

When the Omohyoid (Inferior Belly) contracts, it produces the following movement: Depresses and steadies the hyoid bone.

As part of the Neck group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Omohyoid (Inferior Belly) receives its nerve supply from the Ansa cervicalis (C2–C3). This nerve carries fibres from spinal segment(s) C2, C3.

Because a muscle can only contract when its nerve is intact, injury to the Ansa cervicalis or to its spinal roots (C2, C3) can weaken or paralyse the Omohyoid (Inferior Belly), impairing the movements it normally produces (depresses and steadies the hyoid bone). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Omohyoid (Inferior Belly) (the OIANS method)

Remember the inferior belly by its unusual scapular origin, which makes the omohyoid the only strap muscle to reach the shoulder girdle. Trace it from the superior border of the scapula forward to the intermediate tendon near the clavicle, and you will understand how a muscle attached so far laterally can still contribute, through its tendon, to depressing and steadying the hyoid.

For the nerve, contrast the two bellies: the inferior belly is supplied by the ansa cervicalis proper (C2 to C3), while the superior belly takes the superior root (C1). Fixing that division in mind, along with the belly's diagnostic crossing of the posterior triangle, keeps the omohyoid clearly organised in your notes.

Frequently asked questions

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