Sternocleidomastoid muscle

Sternocleidomastoid muscle

Muscle infobox
Name = Sternocleidomastoid
Latin = musculus sternocleidomastoideus
GraySubject = 111
GrayPage = 390

Caption = The triangles of the neck. (Anterior triangles to the left; posterior triangles to the right.)

Caption2 = Muscles of the neck. Lateral view.
Origin = manubrium sterni, medial portion of the clavicle
Insertion = mastoid process of the temporal bone, superior nuchal line
Blood = occipital artery and the superior thyroid artery
Nerve = motor: accessory nerve
sensory: cervical plexus
Action = Acting alone, tilts head to its own side and rotates it so the face is turned towards the opposite side.Acting together, flexes the neck, raises the sternum and assists in forced inspiration.
DorlandsPre = m_22
DorlandsSuf = 12550942
In human anatomy, the sternocleidomastoid (pronounced IPA|/ˌstɚ.noˌkli.dəˈmæs.tɔɪ̯d/) muscle, also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial layers of the anterior portion of the neck. It acts to flex and rotate the head.

It also acts as an accessory muscle of inspiration, along with the scalene muscles of the neck.


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.

Origin and insertion

The sternocleidomastoid passes obliquely across the side of the neck.

It is thick and narrow at its central part, but broader and thinner at either end.

* The medial or sternal head is a rounded fasciculus, tendinous in front, fleshy behind, which arises from the upper part of the anterior surface of the manubrium sterni, and is directed superiorly, laterally, and posteriorly.

* The lateral or clavicular head, composed of fleshy and aponeurotic fibers, arises from the superior border and anterior surface of the medial third of the clavicle; it is directed almost vertically upward.

The two heads are separated from one another at their origins by a triangular interval, but gradually blend, below the middle of the neck, into a thick, rounded muscle which is inserted, by a strong tendon, into the lateral surface of the mastoid process, from its apex to its superior border, and by a thin aponeurosis into the lateral half of the superior nuchal line of the occipital bone.

Nerve supply

The sternocleidomastoid is innervated by the ipsilateral accessory nerve. It supplies only motor fibres. The cervical plexus supplies sensation including proprioception.


The sternocleidomastoid varies much in the extent of its origin from the clavicle: in some cases the clavicular head may be as narrow as the sternal; in others it may be as much as 7.5 cm in breadth.

When the clavicular origin is broad, it is occasionally subdivided into several slips, separated by narrow intervals. More rarely, the adjoining margins of the Sternocleidomastoid and Trapezius are in contact. This would leave no posterior triangle.

The Supraclavicularis muscle arises from the manubrium behind the Sternocleidomastoid (also known as the wing and named after a large prehistoric bird) and passes behind the Sternocleidomastoid to the upper surface of the clavicle.


The sternocleidomastoid is within the investing fascia of the neck, along with the trapezius muscle, with which it shares its nerve supply (the accessory nerve). Anterior to sternocleidomastoid is the anterior cervical triangle. Posterior to it is the posterior cervical triangle.

Many important structures relate to the sternocleidomastoid, including the common carotid artery, accessory nerve, and brachial plexus.

Cultural significance

* Tom Wolfe's The Bonfire of the Vanities featured a lawyer fond of clenching his sternocleidomastoid muscles.
* In the Portuguese movie A Canção de Lisboa, the main character, Vasco, who is studying Medicine, is asked in his final exam where the Sternocleidomastoid muscle is located. The name of the muscle became famous in Portugal after this movie.


External links


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Look at other dictionaries:

  • sternocleidomastoid muscle — noun one of two thick muscles running from the sternum and clavicle to the mastoid and occipital bone; turns head obliquely to the opposite side; when acting together they flex the neck and extend the head • Syn: ↑sternocleidomastoid,… …   Useful english dictionary

  • sternocleidomastoid muscle — noun A paired muscle in the superficial layers of the anterior portion of the neck, acting to flex and rotate the head. Syn: sternomastoid …   Wiktionary

  • sternocleidomastoid muscle — see sternomastoid muscle * * * musculus sternocleidomastoideus …   Medical dictionary

  • sternocleidomastoid muscle — see sternomastoid muscle …   The new mediacal dictionary

  • sternocleidomastoid — noun one of two thick muscles running from the sternum and clavicle to the mastoid and occipital bone; turns head obliquely to the opposite side; when acting together they flex the neck and extend the head • Syn: ↑sternocleidomastoid muscle,… …   Useful english dictionary

  • sternocleidomastoid — 1. adjective Relating to or involving the sternum, the clavicle and the mastoid process. 2. noun The sternocleidomastoid muscle …   Wiktionary

  • sternocleidomastoid vein — noun drains the sternocleidomastoid muscle; empties into the internal jugular vein • Syn: ↑vena sternocleidomastoidea • Hypernyms: ↑vein, ↑vena, ↑venous blood vessel …   Useful english dictionary

  • Muscle — is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart… …   Medical dictionary

  • muscle — muscleless, adj. muscly, adj. /mus euhl/, n., v., muscled, muscling, adj. n. 1. a tissue composed of cells or fibers, the contraction of which produces movement in the body. 2. an organ, composed of muscle tissue, that contracts to produce a… …   Universalium

  • Muscle — For other uses of Muscle , see Muscle (disambiguation). A top down view of skeletal muscle Muscle (from Latin …   Wikipedia

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