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FUNCTIONAL ANATOMY education The trapezius is a large, powerful muscle that covers a kite-shaped area, extending from the base of the skull downward over the thoracic spine and laterally to the clavicle and spine of the scapula. The trapezius can be divided into three distinct sections: upper, middle, and lower. The upper portion begins at the occiput and nuchal ligament, then extends laterally and anteriorly to the spine of the scapula, acromion process, and clavicle, wrapping laterally around the neck from head to shoulder like a cape. The muscle is thickest where the fibers converge between the spine of the scapula and clavicle, as it curves around the shoulder girdle. When activated, the upper fibers are responsible for shrugging motions or elevation of the scapula, as well as extension, lateral flexion, and rotation of the head and neck to the opposite side. The middle portion lies horizontally, extending from the spinous processes of the seventh cervical and upper thoracic vertebrae to the spine of the scapula. This portion works in tandem with the rhomboids to pull the scapula toward the midline or retract the scapula. Both the middle and upper portions of the trapezius serve as important postural stabilizers of the head, neck, and shoulder girdle. The fibers of the lower portion of the trapezius extend from the spinous processes of the lower thoracic vertebrae upward and laterally to the spine of the scapula. This orientation allows this portion to depress the scapula. The upper and lower fibers work together to upwardly rotate the scapula. When all portions of the trapezius work together, the scapula is fixed on the rib cage, allowing strong support during weight- bearing and pushing activities. When the upper extremity is not fixed, the different fibers of the trapezius work with other synergist muscles to accomplish specific movements of the scapula, such as elevation, retraction, or depression. The trapezius's function in upward rotation of the scapula helps optimally position the shoulder girdle during overhead motions, thereby enhancing range of motion in the glenohumeral joint. Trapezius By Christy Cael 40 m a s s a g e & b o d y w o r k j a n u a r y / f e b r u a r y 2 0 1 9 TRAPEZIUS Attachments • Origin: Occiput, nuchal ligament, and spinous processes of C7–T12 • Insertion: Lateral 1 /3 of the clavicle, acromion process, and spine of the scapula Actions • Extends, laterally flexes, and rotates head and neck to same side (contralaterally) • Elevates and upwardly rotates scapula (upper fibers) • Retracts scapula (entire muscle) • Depresses and upwardly rotates scapula (lower fibers) Innervation • Medial and lateral pectoral nerves • C5–T1 Trapezius muscle