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
The omohyoid muscle is innervated by the ansa cervicalis from the cervical plexus (C1-3)
External links
Musculoskeletal Anatomy
Category:Muscles of the head and neck
