Muscles / Head & neck
Sternocleidomastoid
- Head & neck
- Neck
- Superficial layer
Also called SCM.
Anatomy
- Origin
- Sternal head: anterior surface of the manubrium; clavicular head: superior surface of the medial third of the clavicle
- Insertion
- Lateral surface of the mastoid process and lateral half of the superior nuchal line
- Nerve
- Spinal accessory nerve (CN XI), motor; C2-C3 (pain and proprioception) (CN XI; C2-C3 sensory)
Actions
- Unilaterally: laterally flexes the neck and rotates the face to the opposite side
- Bilaterally: flexes the neck; protracts the head
- Accessory muscle of inspiration when the head is fixed
Notes
- Over-activity of SCM during the craniocervical flexion test indicates substitution for weak deep neck flexors.
- Shortened in congenital muscular torticollis.
References (5)
- Jull GA, O'Leary SP, Falla DL. J Manipulative Physiol Ther. 2008;31(7):525-533. Clinical assessment of the deep cervical flexor muscles: the craniocervical flexion test
- Standring S, ed. Elsevier. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed.
- Dalley AF, Agur AMR. Wolters Kluwer. Moore's Clinically Oriented Anatomy. 9th ed.
- Neumann DA. Elsevier. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed.
- Betts JG, Young KA, Wise JA, et al. OpenStax (free, openly licensed textbook). Anatomy and Physiology 2e