Muscular system · Head and neck
Omohyoid !
The omohyoid is a two-bellied strap muscle that crosses the neck from the shoulder blade to the hyoid bone; it pulls the hyoid down.
Official name: Omohyoid muscle
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What it is
A two-bellied strap muscle from the shoulder blade to the hyoid, crossing the neck.
What it does
Pulls the hyoid down; a landmark over the carotid sheath.
Key facts
- Origin
- Inferior belly: superior border of the scapula near the notch
- Insertion
- Superior belly: body of the hyoid (intermediate tendon held to the clavicle)
- Action
- Depresses the hyoid
- Nerve
- Ansa cervicalis (C1–C3)
- Blood supply
- Transverse cervical and superior thyroid arteries
Relations
- Course
- The inferior belly runs forward from the upper border of the scapula across the lower posterior triangle; the intermediate tendon passes deep to the sternocleidomastoid; the superior belly then rises almost vertically beside the sternohyoid to the hyoid bone
- Deep
- Under the tendon, the carotid sheath (internal jugular vein, common carotid artery, vagus nerve); under the inferior belly, the scalenes, the brachial plexus trunks and the phrenic nerve
- Superficial
- Sternocleidomastoid over the tendon; platysma and the investing cervical fascia over the inferior belly
- Medial
- Sternohyoid, beside the superior belly
How to find it
In surgery the intermediate tendon is found deep to the sternocleidomastoid lying across the internal jugular vein; on neck ultrasound it is the thin band crossing the vein, used to tell level III from level IV.
On imaging
On ultrasound and CT the intermediate tendon is the thin band crossing over the internal jugular vein deep to the sternocleidomastoid; surgeons use it to separate node levels III and IV, while radiologists use the lower border of the cricoid. In the supraclavicular region the inferior belly crosses superficial to the brachial plexus, a landmark during ultrasound-guided blocks.
Clinical notes
- Supraomohyoid (selective) neck dissection is typical for cancers of the oral cavity, whose lymph drains first to levels I–III
- Branches of the ansa cervicalis to both bellies run on the carotid sheath, so the muscle helps find the ansa during neck surgery
- In supraclavicular exposure of the brachial plexus the inferior belly is met crossing the lower posterior triangle and is retracted or divided to reach the plexus trunks and the scalene muscles
Development
One of the strap muscles, formed from the premuscle mass continuous with the tongue's and supplied by the upper cervical nerves that enter it early (ansa cervicalis).
Memory aid
Omos is Greek for shoulder: the omohyoid runs from the shoulder blade to the hyoid.
Test yourself
Think of the answer, then tap the question to see it.
Which node levels does the omohyoid tendon separate where it crosses the internal jugular vein?
Levels III and IV: the intermediate tendon crosses the vein at about the level of the cricoid cartilage.
How do the two bellies of the omohyoid subdivide the neck triangles?
Superior belly: anterior triangle into carotid and muscular triangles; inferior belly: posterior triangle into occipital and supraclavicular.
Which node levels does a supraomohyoid neck dissection remove, and for which cancers is it typical?
Levels I–III, above where the omohyoid crosses the jugular vein; typical for oral cavity cancers, which drain first to these levels.
What is the nerve supply of the omohyoid?
The ansa cervicalis (C1–C3), whose branches run on the carotid sheath, so the muscle helps find the ansa in neck surgery.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- musculus omohyoideus TA2 2169
- Official Spanish (DeCS)
- Músculo omohioideo
- English (TA2)
- Omohyoid muscle
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Head and Neck: Anterior Cervical Region; Anatomy, Head and Neck, Neck; Anatomy of the Human Body (20th ed.): Development of the Muscles (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.
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Representative model, for educational purposes only.
