Neck - Superficial Muscles
Sternocleidomastoid
- Sternal head originates on the manubrium;
- Clavicular head originates on the medial 1/3rd of the clavicle.
- Both insert on the mastoid process of the temporal bone.
- Unilateral contraction laterally flexes the neck and rotates the head to turn the face to the opposite side.
- Bilateral contraction extends the neck at the base of the head (if the posterior fibers contract) or, flexes the neck so that the chin moves toward the sternum (if the anterior fibers contract).
- Sternocleidomastoid divides the cervical region into anterior and posterior triangles.
- Originates on the external occipital protuberance, the nuchal ligament over the cervical vertebrae, and the spinous processes of the thoracic vertebrae; it inserts along the lateral 1/3rd of the clavicle and also the acromion and spine of the scapula.
- Trapeziuseither adducts, rotates, elevates, or depresses the scapula based on which muscle fiber region contracts.
Platysma:
- Originates on the superficial fascia over the superior shoulder and chest, and inserts into the skin and muscles of the mandible; it depresses the skin of the neck and lower lip and angle of the mouth.