Ans. is 'D' i.e.. Tilt the head on opposite side Sternocleidomastoid (sternomastoid) Origin 1. The, sternal head is tendinous and arises from the superolateral part of the front of the manubrium stemi. 2. The clavicular head is musculotendinous and arises from the medial one-third of the superior surface of the clavicle. It passes deep to the sternal head, and the twro heads blend below' the middle of the neck. Between the two heads, there is a small triangular depression of the lesser supraclavicular fossa, overlying the internal jugular vein. Insertion o It is inserted : 1. By a thick tendon into the lateral surface of mastoid process, from its tip to superior border. 2. By a thin apponeurosis into the lateral half of the superior nuchal line of the occipital bone. Nerve supply 1. The spinal accessor}' nerve provides the motor supply. It passes through the muscle. 2. Branches from the ventral rami of C2 are proprioceptive. Blood supply o Arterial supply-one branch each from superior thyroid artery and suprascapular artery and, two branches from the occipital artery' supply the big muscle, o Veins follow the arteries. Actions 1. When one muscle contracts : It turns the chin to the opposite side. It can also tilt the head towards the shoulder of same side. 2. When both muscles contract together : They draw the head forwards, as in eating and in lifting the head from a pillow. With the longus colli, they flex the neck against resistance. It also helps in forced inspiration.