Sternocleidomastoid muscle

Start: upper margin of anterior part of manubrium sterni, upper surface of extremitas sternalis claviculae.

Tendril: processus mastoideus, lateral part of linea nuchalis superior.

Innervation: n. accessorius and fibres from C2-C4.

Function:

- Bowing of the head to the same side and rotation to the opposite (unilateral contraction);

- forward movement and forward tilt of the head (bilateral contraction);

- posterior bundles of head flexion.

Wedge: when m. sternocleidomastoideus is shortened, there is a striking tilt of the head to the ipsilateral side of the affected muscle and rotation to the opposite side. The condition is called torticollis.