The omohyoid muscle is a muscle in the neck. It is one of the infrahyoid muscles. It consists of two bellies separated by an intermediate

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

. Its inferior belly is attached to the

scapula The scapula (: 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 either side ...

; its superior belly is 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 verte ...

. Its intermediate tendon is anchored to the clavicle and first rib by a fascial sling. The omohyoid is innervated by the ansa cervicalis of the

cervical plexus The cervical plexus is a nerve plexus of the anterior rami of the first (i.e. upper-most) four cervical spinal nerves C1-C4. The cervical plexus provides motor innervation to some muscles of the neck, and the diaphragm; it provides sensory inne ...

. It acts to depress the hyoid bone.

Anatomy

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. It arises from the superior border of scapula (near the scapular notch). It sometimes also arises from the superior transverse scapular ligament. It is directed anteriorly and somewhat superiorly from its origin, extending across the inferior portion of the neck. It passes posterior to the

sternocleidomastoid muscle 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 Anatomical terms of motion#Flexion and extension, flexion of the neck. ...

to insert at the intermediate tendon.

Superior belly

The superior belly arises at the intermediate tendon. It extends nearly vertically superior-ward close to the lateral border of

to insert at the inferior border of the

body of 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 verte ...

(its site of insertion is lateral to that of the sternohyoid muscle).

Intermediate tendon

The intermediate tendon is variable in length and form, and contains a variable amount of muscle tissue. It is anchored inferiorly to the clavicle and first rib by a band of

deep cervical fascia The deep cervical fascia (or fascia colli in older texts) lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its ...

that surrounds the intermediate tendon; this fascial fixation maintains the angle of the muscle. It is typically situated at the level of the arch of cricoid cartilage, adjacent to 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 ...

Innervation

The omohyoid is innervated by the ansa cervicalis of the

. 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)).

Relations

The inferior belly of the omohyoid divides the posterior triangle of the neck into a occipital triangle (above) and a subclavian triangle (below). Its superior belly divides the anterior triangle into an carotid triangle (above) and a muscular triangle (below).Human anatomy, Jacobs, Elsevier, 2008, page 189 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 The tendon is related to the

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

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 m ...

, giving one of its attachments, and "

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 verte ...

", giving the other attachment – the hyoid bone.

References

External links

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