Sternomastoid

Sternocleidomastoid
Neck muscles, with the sternocleidomastoid shaded.
The right sternocleidomastoid can be clearly observed when rotating the head.
Details
Origin	Manubrium and medial portion of the clavicle
Insertion	Mastoid process of the temporal bone, superior nuchal line
Artery	Occipital artery and the superior thyroid artery
Nerve	Motor: accessory nerve sensory: cervical plexus
Actions	Unilaterally: contralateral cervical rotation, ipsilateral cervical flexion Bilaterally: cervical flexion, elevation of sternum and assists in forced inhalation.
Identifiers
Latin	Musculus sternocleidomastoideus
Dorlands /Elsevier	m_22/12550942
TA	A04.2.01.008
FMA	13407
Anatomical terms of muscle []

Unilaterally: contralateral cervical rotation, ipsilateral cervical flexion

In human anatomy, the sternocleidomastoid muscle (/ˌstɜːrnoʊˌklaɪdəˈmæsˌtɔɪd, -nə-, -doʊ-/), also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial layers of the side of the neck. It 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 flexion of the neck. The sternocleidomastoid is innervated by the accessory nerve.

It is given the name sternocleidomastoid because it originates at the manubrium of the sternum (sterno-) and the clavicle (cleido-), and has an insertion at the mastoid process of the temporal bone of the skull.