sternocleidomastoid

Introduction

Superficial muscle of the anterolateral neck.

Origin

(by 2 heads)

• anterior surface of the manubrium of the sternum
• sternal end of the clavicle

Insertion

• mastoid process
• lateral 1/2 of superior nuchal line

Action

• turns head obliquely to the opposite side
• when acting bilaterally together, flexes neck & extends head

Innervation

• motor: accessory nerve (CN XI)
• sensory: cervical plexus

More general terms

• skeletal muscle (voluntary muscle)