The Sternocleidomastoid Muscle
Definition
Neck muscle
Also called sternomastoid
Paired : left and right
Origin and insertion
Orginates from manubrium sterni and clavicle by two heads - sternal and clavicular heads
Inserted into the mastoid process of the temporal bone of the skull
Relations
The muscle is related to the muscles in the posterior triangle of the neck viz. the splenius capitis, levatro scapulae, scalene muscles - scalenus anterior, scalenus medius and scalenus posterior
Closely related to the common carotid artery and the internal jugular vein
Anteriorly to the strap muscles of the neck
Blood supply
Artery : Occipital artery and the superior thyroid artery
Nerve supply
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
Applied Anatomy
Torticolis - spastic sternocleidomastoid muscle
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