The sternocleidomastoid muscles are long and extend from the thorax to the base of the skull just behind the ear on both sides of the neck. Each muscle passes obliquely across the side of the neck. The sternocleidomastoid muscles flex the neck and assist with oblique neck rotation. When one of the sternocleidomastoid muscles contracts, the face turns to the opposite side. When both muscles contract the head bends toward the chest.
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The sternocleidomastoid muscles raise the sternum (breastbone), which aids in forceful inspiration (inhalation, breathing in).
Origin - The sternocleidomastoid originates at the anterior and superior manubrium and superior medial third of the clavicle (collarbone).
Insertion - The sternocleidomastoid inserts into the lateral part of the mastoid process and the anterior half of the superior nuchal line.
Action - The sternocleidomastoid is primarily responsible for flexing the neck and extending the head. It's also called the sternocleidomastoid and commonly abbreviated as SCM.
Nerve Supply - The sternocleidomastoid is innervated by two nerves: the cervical plexus nerve which provides sensory function; and the spinal accessory nerve which aids in motor function.
Blood Supply – The sternocleidomastoid is supplied with blood by the occipital artery and the superior thyroid artery.
Anomalous Medical is a great way to explore the Sternocleidomastoid and other muscles in 3D. View both Sternocleidomastoid muscles from any angle.