Anatomy

Origin

Trapezius - Upper Head: Medial third of superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes and supraspinous ligaments of seventh cervical vertebra Trapezius - Middle Head: Spinous processes and supraspinous ligaments of seventh cervical and first 4-5 thoracic vertebrae Trapezius - Lower Head: Spinous processes and supraspinous ligaments of thoracic vertebrae from 5 to 12

Insertion

Trapezius - Upper Head: Lateral third of clavicle Trapezius - Middle Head: Acromion and spine of scapula Trapezius - Lower Head: Medial portion of spine of scapula (tubercle)

Nerve

Accessory (eleventh cranial), C3, C4

Actions

Trapezius - Upper Head: Elevates scapula, stabilizes scapula against downward rotation, as when weight is carried in the hand. Trapezius - Middle Head: Retracts (adducts) scapula Trapezius - Lower Head: Depresses scapula Trapezius - Upper Head and Lower Head together rotate scapula (important in elevating arm)