Along with the latissimus dorsi, rhomboids, and levator scapula, the trapezius muscle is one of the widest back muscles. Broad muscle bands cross the back, providing upright posture support. The trapezius and semispinalis capitis muscles create a muscle column along the back portion of the neck. The trapezius is the most superficial (nearest to the skin) of the back, neck, and upper trunk muscles. This triangular muscle is broad and flat, lying just beneath the skin and covering the upper back of the shoulders and neck. It links to the dorsal vertebrae of the spine, scapulae, clavicles, and ribs. This muscle is named for its trapezoid shape. The trapezius muscle is a postural and active movement muscle, used to tilt and turn the head and neck, shrug, steady the shoulders, and twist the arms. The trapezius elevates, depresses, rotates, and retracts the scapula, or shoulder blade. Innervation of the trapezius is derived from the spinal accessory nerve. The descending part of the trapezius muscle supports the arms. The transverse part retracts the scapulae, and the ascending part medially rotates or depresses the scapulae.