Sternocleidomastoid Muscle Variations

The Sternocleidomastoid Muscle Variations

Describe the sternocleidomastoid muscle in brief.
Answer.

The sternocleidomastoid muscle is a large superficial muscle of the neck. It lies obliquely on the side of the neck between anterior and posterior triangles. It stands out prominently when the head is turned to the opposite side.

Sternocleidomastoid Muscle Origin It arises by two heads – sternal and clavicular.

1. Sternal head: By a rounded tendon from the upper part of the anterior surface of the manubrium sterni.
2. Clavicular head: By the musculoaponeurotic fibres from the superior border and anterior surface of the medial one-third of the clavicle.

Insertion By a strong tendon into the lateral surface of the mastoid process and by thick aponeurosis into the lateral half of the superior nuchal line of the occipital bone.

Sternocleidomastoid Muscle Nerve supply

• Spinal accessory nerve (motor)
• Ventral rami of C2 and C3 (proprioceptive)

Sternocleidomastoid Muscle Actions

• Tilts the head towards the shoulder on the same side and simultaneously rotates the head in such a way that the face is turned to the opposite side and upwards.
• Both the muscles acting together draw the head forward and downwards, as in lifting/elevating the head from the pillow when lying down on the bed in the supine position.

Sternocleidomastoid Muscle Applied anatomy

Torticollis: It is a deformity of the neck in which the head is bent to one side and the chin faces towards the opposite side. It occurs due to spasm or contracture of the sternocleidomastoid muscle.