How to Identify the Sternocleidomastoid

The sternocleidomastoid is a muscle of the anterior neck that flexes and rotates the head. It also acts with the scalene muscles to assist with inspiration. It is narrow and thick at the central part but broader and thinner at each end. The following steps will help you identify the sternocleidomastoid muscle.

Difficulty: Moderate

Instructions

1. Read up on Latin roots to know that "sterno" means "chest," "cleido" means "clavicle" and "mastoid" means "breast shaped." This muscle attaches to the chest (sternum), clavicle (key shape) and mastoid (breast-shaped) process.

2. Examine the sternocleidomastoid to see that it laterally rotates the cervical spine to the opposite side of the contraction, laterally flexes to the contracted side and bilaterally flexes the neck.

3. Observe how the medial head of the sternocleidomastoid originates from the anterior and superior part of the manubrium sterni and the lateral head originates from the superior medial third of the clavicle.

4. Look at the insertion of the sternocleidomastoid into the lateral aspect of the mastoid process of the temporal bone and the anterior half of the superior nucal line of the occipital bone by a thin aponeurosis.

5. Research the nervous system to know that the nerve for the sternocleidomastoid is the spinal accessory (11th cranial nerve) for motor and the ventral rami of the second and third cervical nerves for sensory.

6. Study the circulatory system to know that the blood supply for the sternocleidomastoid is the occipital artery and the superior thyroid artery.

Resources

• Read a medical glossary.