Origin: Base of skull(occipital bone) Spinous processes of C7 through T12.
Insertion: Lateral third of clavicle, acromion process, spine of scapula.
Upper fibers: elevation of scapula, upward rotation, extension and rotation of head at neck.
Middle fibers: elevation, upward rotation, and adduction(retraction) of scapula.
Lower Fibers: depression, adduction(retraction), and upward rotation of the scapula.