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 mus ...

that depresses the hyoid. 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 eith ...

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 verteb ...

, stabilising it. Its superior belly serves as the most lateral member of the infrahyoid muscles, 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, 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, to be inserted into the lower border of the body of the

, lateral to the insertion of the sternohyoid. 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 r ...

and first rib; it is by this means that the angular form of the muscle is maintained. The tendon overlies 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. It may originate from the clavicle rather than the scapula. It occasionally arises from the superior transverse scapular ligament, which crosses the scapular notch, 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 me ...

, 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. Bra ...

. 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 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 into an upper or occipital triangle and a lower or subclavian triangle. Its superior belly divides the anterior triangle into an upper carotid triangle and a lower muscular triangle.Human anatomy, Jacobs, Elsevier, 2008, page 189

Name

The name "omohyoid" derives from the Greek "omos" meaning shoulder, giving one of its attachments, and " hyoid", giving the other attachment – the hyoid bone.

References

External links

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