Structure The omohyoid muscle consists of
muscle bellies that meet at an angle at the muscle's intermediate tendon.
Inferior belly The inferior belly is narrow and flat band. The inferior belly is innervated by the
ansa cervicalis itself (which is derived from cervical spinal nerves C1-C3), and the superior belly is innervated by the
superior root of ansa cervicalis (which is derived from the
first cervical spinal nerve (C1)). Its superior belly divides the
anterior triangle into an
carotid triangle (above) and a
muscular triangle (below). Its superior belly serves as the most lateral member of the
infrahyoid muscles, located lateral to both the
sternothyroid muscles and the
thyrohyoid muscles. The tendon is related to the
internal jugular vein and can be used as a landmark for this vein during surgery.
Variation The omohyoid muscle may be doubled or completely absent in some people. Either belly may be doubled or absent. The inferior belly may be attached to the clavicle directly (rather than by fascia). The superior belly may be fused with the
sternohyoid muscle.
Actions/movements The muscle depresses the hyoid bone when the bone is in an elevated position. A putative action of the muscle is tension of the inferior portion of deep cervical fascia to prevent soft tissues from collapsing inward into the upper airway during deep inspiration. == Etymology ==