Omohyoid muscle

Omohyoid muscle
Side of neck, showing chief surface markings. (Omohyoid visible at center.)
Muscles of the neck. Anterior view. Omohyoid is labeled on both sides.
Latin	musculus omohyoideus
Gray's	subject #112 392
Origin	Upper border of the scapula
Insertion	Hyoid bone
Artery
Nerve	Ansa cervicalis (C1-C3)
Actions	Depresses the larynx and hyoid bone. Also carries hyoid bone backward and to the side.

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.

Structure

It arises from the upper border of the scapula, 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.

Triangles

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 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.

Variations

Doubling; absence; origin from clavicle; absence or doubling of either belly.

Innervation

The omohyoid is innervated by a branch of the cervical plexus, 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).

Additional images

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  Hyoid bone. Anterior surface. Enlarged.

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  Left scapula. Dorsal surface.

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  Section of the neck at about the level of the sixth cervical vertebra. Showing the arrangement of the fascia coli.

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  Muscles of the neck. Lateral view.

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  Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.

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  The veins of the neck, viewed from in front.

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  Hypoglossal nerve, cervical plexus, and their branches.

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  The right brachial plexus with its short branches, viewed from in front.

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  Musculi colli omohyoideus

The omohyoid muscle is innervated by the ansa cervicalis from the cervical plexus (C1-3)

External links

• -1335164848 at GPnotebook
• SUNY Labs 24:06-0100
• SUNY Figs 24:01-09
• LUC omo
• lesson6 at The Anatomy Lesson by Wesley Norman (Georgetown University)

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.