Trapezius Muscle: Location, Anatomy & Function - MuscleWiki

The trapezius muscle is a large, superficial muscle that runs from the base of the skull to the middle of the back. It has three parts: the upper trapezius, the middle trapezius, and the lower trapezius.

* The upper trapezius extends from the occipital bone of the skull to the clavicle (collarbone). It helps to raise the shoulders and shrug them upwards.

* The middle trapezius extends from the spinous processes of the vertebrae C7-T12 to the scapula (shoulder blade). It helps to retract the scapula and pull it closer to the spine.

* The lower trapezius extends from the spinous processes of the vertebrae T12-L5 to the scapula. It helps to depress the scapula and pull it downwards.

The trapezius muscle is innervated by the accessory nerve (cranial nerve XI).