Saturday, 15 November 2014

The Sternocleido-Mastoid Muscle Detail

The sternocleidomastoid  muscle:-

   In human anatomy, the sternocleidomastoid 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 is one of the largest and most superficial cervical muscles.


Structure:-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 (supraclavicular fossa) 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.usculus sternocleidomastoideus

Origin:-
    Manubrium sterni 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; cervical rotation to opposite side, 
                            cervical lateral flexion to same side
                         Bilaterally; cervical flexion, raises the sternum and assists in forced inspiration.


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