The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports the arm. The trapezius has three functional parts: an upper (descending) part, which supports the weight of the arm; a middle region (transverse), which retracts the scapula; and a lower (ascending) part, which medially rotates and depresses the scapula.

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