The omohyoid muscle is a

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

that depresses the

hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebra. ...

. It is located in the front of the

neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...

, and consists of two bellies separated by an intermediate

tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

. The omohyoid muscle is proximally attached to the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

and distally attached to the

hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebr ...

, stabilising it. Its superior belly serves as the most lateral member of the

infrahyoid muscles The infrahyoid muscles, or strap muscles, are a group of four pairs of muscles in the anterior (frontal) part of the neck. The four infrahyoid muscles are the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles. Excluding the sternothyr ...

, located lateral to both the sternothyroid muscles and the thyrohyoid muscles.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 102

Structure

The omohyoid muscle arises from the upper border of the

, inserting into the lower border of the body of the

. It has two separate bellies, superior and inferior: * The ''inferior belly'' forms a flat, narrow

fasciculus ''Fasciculus vesanus'' is an extinct species of stem-group ctenophores known from the Burgess Shale of British Columbia, Canada. It is dated to and belongs to middle Cambrian strata. The species is remarkable for its two sets of long and short ...

, which inclines forward and slightly upward across the lower part of the neck, being bound down to the clavicle by a fibrous expansion; it then passes behind the

sternocleidomastoid The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the access ...

, becomes tendinous and changes its direction, forming an obtuse angle. * The ''superior belly'' passes almost vertically upward, close to the lateral border of the

sternohyoid The sternohyoid muscle is a thin, narrow muscle attaching the hyoid bone to the sternum. It is one of the paired strap muscles of the infrahyoid muscles. It is supplied by the ansa cervicalis. It depresses the hyoid bone. Structure The sternohy ...

, to be inserted into the lower border of the body of the

, lateral to the insertion of the

. The central

of this muscle varies much in length and form, and is held in position by a process of the deep cervical fascia, which sheaths it, and is prolonged down to be attached to the

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

and first rib; it is by this means that the angular form of the muscle is maintained. The tendon overlies the

internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the posteri ...

, 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. It may originate from the clavicle rather than the scapula. It occasionally arises from the

superior transverse scapular ligament The superior transverse ligament (transverse or suprascapular ligament) converts the suprascapular notch into a foramen or opening. It is a thin and flat fascicle, narrower at the middle than at the extremities, attached by one end to the base of ...

, which crosses the

scapular notch The suprascapular notch (or ''scapular notch'') is a notch in the superior border of the scapula, just medial to the base of the coracoid process. It forms the entrance site into the suprascapular canal. Structure This notch is converted into ...

, its extent of attachment to the scapula varying from a few millimetres to 2.5 cm.

Innervation

The omohyoid is innervated by a branch of the

cervical plexus The cervical plexus is a plexus of the anterior rami of the first four cervical spinal nerves which arise from C1 to C4 cervical segment in the neck. They are located laterally to the transverse processes between prevertebral muscles from the medi ...

, the

ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin. Branc ...

. The inferior belly of the omohyoid is innervated by the three cervical branches (C1-C3) that make up the

, while the superior belly is innervated by the

superior root of ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin. Branch ...

which contains only fibers from the first cervical spinal nerves (C1).

Examination of the neck

The inferior belly of the omohyoid divides the

posterior triangle of the neck Posterior may refer to: * Posterior (anatomy), the end of an organism opposite to its head ** Buttocks, as a euphemism * Posterior horn (disambiguation) * Posterior probability, the conditional probability that is assigned when the relevant evidenc ...

into an upper or

occipital triangle The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

and a lower or

subclavian triangle The subclavian triangle (or supraclavicular triangle, omoclavicular triangle, Ho's triangle), the smaller division of the posterior triangle, is bounded, above, by the inferior belly of the omohyoideus; below, by the clavicle; its base is formed by ...

. Its superior belly divides the

anterior triangle The anterior triangle is a region of the neck. Structure The triangle is inverted with its apex inferior to its base which is under the chin. Investing fascia covers the roof of the triangle while visceral fascia covers the floor. Anatomy Mu ...

into an upper

carotid triangle The carotid triangle (or superior carotid triangle) is a portion of the anterior triangle of the neck. Coverings and boundaries It is bounded: * Posteriorly by the anterior border of the Sternocleidomastoid; * Anteroinferiorly, by the superior be ...

and a lower

muscular triangle The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the sternocleidomastoid; above, by the superior belly of the omohyoid ...

.Human anatomy, Jacobs, Elsevier, 2008, page 189

Name

The name "omohyoid" derives from the Greek "omos" meaning

shoulder The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...

, giving one of its attachments, and "

", giving the other attachment – the hyoid bone.

References

External links

* * * {{Authority control Muscles of the head and neck