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Sternocleidomastoid muscle

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Attachments, innervations and functions of the sternocleidomastoid muscle.

The sternocleidomastoid muscle is a two-headed neck muscle, which true to its name bears attachments to the manubrium of sternum (sterno-), the clavicle (-cleido-), and the mastoid process of the temporal bone (-mastoid). 

It is a long, bilateral muscle of the neck, which functions to flex the neck both laterally and anteriorly, as well as rotate the head contralaterally to the side of contraction.

The muscle is closely related to certain neurovascular structures that pass through the neck on their way either to the head or to the periphery of the body.

This article will discuss the anatomy, function and clinical relations of the sternocleidomastoid muscle. 

Key facts
Origins Sternal head: superior part of anterior surface of manubrium sterni
Clavicular head: superior surface of medial third of the clavicle
Insertions Lateral surface of mastoid process of the temporal bone, Lateral half of superior nuchal line of the occipital bone
Innervation Accessory nerve (CN XI), branches of cervical plexus (C2-C3)
Blood supply Superior thyroid artery
Functions Unilateral contraction: cervical spine: neck ipsilateral flexion, neck contralateral rotation
Bilateral contraction: atlantooccipital joint/ superior cervical spine: head/neck extension; Inferior cervical vertebrae: neck flexion; sternoclavicular joint: elevation of clavicle and manubrium of sternum
Clinical relations Wryneck, torticollis
  1. Origin and insertion
  2. Relations
  3. Innervation
  4. Blood supply
  5. Function
  6. Clinical relations
  7. Sources
+ Show all

Origin and insertion

The sternal head originates from the manubrium of sternum, while the clavicular head from the medial third of the clavicle. The two heads join into one muscle belly that goes on to insert on the lateral surface of the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone.

Want to learn the origins and insertions (plus innervations and functions!) of the sternocleidomastoid muscle 10x faster and easier? You need our head and neck muscle anatomy chart!

Sternocleidomastoid muscle in the neck of the cadaver. Notice its attachments for which it got its name; sterno- (sternum), cleido- (clavicle) and -mastoid (mastoid process).


The muscle lies very superficially so that it is both easily visible and palpable. The carotid pulse may be felt in the middle third of the front edge. Under the sternocleidomastoid region runs a neurovascular bundle containing:

When putting a central venous catheter (CVC), the medial edge of the sternocleidomastoid muscle serves as a lead structure. Sensory branches of the cervical plexus merge dorsally to the muscle at the Erb’s point (punctum nervosum) which can be used as a place of puncture for local anesthesia.

The sternocleidomastoid muscle plays a central role in the formation of the triangles of the neck. Learn everything about those triangles with the following study unit. 


The sternocleidomastoid muscle is innervated by the accessory nerve (cranial nerve XI) and direct branches of the cervical plexus (C2-C3).

Blood supply

Blood supply to the sternocleidomastoid muscle is through the superior thyroid artery, which is a branch of the external carotid artery


A unilateral contraction of the sternocleidomastoid muscle flexes the cervical vertebral column to the same side (lateral flexion) and rotates the head to the opposite side.

A bilateral contraction elevates the head by dorsally extending the upper cervical joints. At the same time, it flexes the lower cervical column causing an overall bending of the neck towards the chest.

If the head is fixed, it elevates the sternum and clavicle and, thus, expands the thoracic cavity (inspiratory breathing muscle).

Test your knowledge about the sternocleidomastoid and other anterior muscles of the neck with the following quiz:

Sternocleidomastoid muscle: want to learn more about it?

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