Trapezius definition

Part shoulder girdle, the trapezius extends from a short horizontal line on the base of the skull to all of the vertebrae down to the 10th thoracic.  It is located at the spine of the scapula, the medial side of the acromion process of the scapula, and the lateral third of the clavicle.  Its upper third raises the scapula.  With the scapula remaining motionless, it draws the head upright, backward, toward the shoulder, and rotates the face to the opposite side. Its middle third brings the scapula towards the spine. The lower third brings it downward. Both sides work together to extend the head.