Omohyoid muscle
Encyclopedia
The omohyoid muscle is a muscle
at the front of the neck
that consists of two bellies separated by an intermediate tendon
. It belongs to the group of infrahyoid muscles. Its name derives from the Greek "omos" meaning shoulder, giving one of its attachments, and "hyoid", giving the other attachment - the hyoid bone.
, and occasionally 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.
From this origin, 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, becomes tendinous and changes its direction, forming an obtuse angle.
It ends in the superior belly, which passes almost vertically upward, close to the lateral border of the sternohyoid, to be inserted into the lower border of the body of the hyoid bone
, lateral to the insertion of the sternohyoid.
The central tendon
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
and first rib; it is by this means that the angular form of the muscle is maintained.
into an upper or occipital triangle
and a lower or subclavian triangle
.
Its superior belly divides the anterior triangle into an upper or carotid triangle and a lower or muscular triangle.
The Omohyoid muscle is proximally attached to the scapula
and distally attached to the hyoid bone
.
, the ansa cervicalis, and mostly acts to stabilise the hyoid bone. Although the inferior belly of the omohyoid is innervated by branches of all three cervical rami (C1-C3) that make up the ansa cervicalis, the superior belly is innervated by the superior root of ansa cervicalis
which contains only fibers from the first cervical spinal nerves (C1).
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
at the front of the neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
that consists of two bellies separated by an intermediate tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
. It belongs to the group of infrahyoid muscles. Its name derives from the Greek "omos" meaning shoulder, giving one of its attachments, and "hyoid", giving the other attachment - the hyoid bone.
Structure
It arises from the upper border of the scapulaScapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
, and occasionally from the superior transverse scapular ligament
Superior transverse scapular ligament
The superior transverse ligament converts the scapular notch into a foramen or opening.It is a thin and flat fasciculus, narrower at the middle than at the extremities, attached by one end to the base of the coracoid process, and by the other to the medial end of the scapular notch.The...
which crosses the scapular notch, its extent of attachment to the scapula varying from a few millimetres to 2.5 cm.
From this origin, the inferior belly forms a flat, narrow fasciculus
Muscle fascicle
In anatomy, a fascicle is a bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue.Specialized muscle fibers in the heart that transmit electrical impulses from the Atrioventricular Node to the Purkinje Fibers are fascicles, also referred to as bundle branches...
, 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, becomes tendinous and changes its direction, forming an obtuse angle.
It ends in the superior belly, which passes almost vertically upward, close to the lateral border of the sternohyoid, to be inserted into the lower border of the body of the hyoid bone
Hyoid bone
The hyoid 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 at the level of the base of the mandible in the front and the third cervical vertebra behind.Unlike other bones, the hyoid is only distantly...
, lateral to the insertion of the sternohyoid.
The central tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
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
Clavicle
In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...
and first rib; it is by this means that the angular form of the muscle is maintained.
Triangles
The inferior belly of the omohyoid divides the posterior triangle of the neckPosterior triangle of the neck
-Boundaries:It has the following boundaries:Apex: Union of the sternocleidomastoid and the trapezius muscles at the superior nuchal line of the occipital boneAnterior: Posterior border of the sternocleidomastoideus...
into an upper or occipital triangle
Occipital triangle
The occipital triangle, the larger division of the posterior triangle, is bounded, in front, by the Sternocleidomastoideus; behind, by the Trapezius; below, by the Omohyoideus....
and a lower or subclavian triangle
Subclavian triangle
The subclavian 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 the posterior border of the Sternocleidomastoideus.Its floor is formed by the first rib with the first digitation of...
.
Its superior belly divides the anterior triangle into an upper or carotid triangle and a lower or muscular triangle.
The Omohyoid muscle is proximally attached to the scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
and distally attached to the hyoid bone
Hyoid bone
The hyoid 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 at the level of the base of the mandible in the front and the third cervical vertebra behind.Unlike other bones, the hyoid is only distantly...
.
Innervation
The omohyoid is innervated by a branch of the cervical plexusCervical plexus
The cervical plexus is a plexus of the ventral rami of the first four cervical spinal nerves which are located from C1 to C4 cervical segment in the neck. They are located laterally to the transverse processes between prevertebral muscles from the medial side and vertebral from lateral side...
, the ansa cervicalis, and mostly acts to stabilise the hyoid bone. Although the inferior belly of the omohyoid is innervated by branches of all three cervical rami (C1-C3) that make up the ansa cervicalis, the superior belly is innervated by the superior root of ansa cervicalis
Superior root of ansa cervicalis
The superior root of the ansa cervicalis is formed by branches of spinal nerves [Cervical spinal nerve 1 and 2 ].These nerve fibers travel in the hypoglossal nerve before separating in the carotid triangle to form the superior root....
which contains only fibers from the first cervical spinal nerves (C1).