The trapezius is an extrinsic muscle of the shoulder. It is a broad, flat and triangular shape – forming a trapezoid shape in combination with the contralateral side. Attachments: Originates from the skull, nuchal ligament and the spinous processes of C7-T12. The fibres attach to the clavicle, acromion, and the scapula spine. Actions: Abduction of the upper limb at the shoulder (by rotating the scapula). The upper fibres of trapezius also elevate the scapula, the middle fibres retract, and the lower fibres depress. Innervation: Accessory nerve Blood supply: Transverse cervical artery By TeachMeSeries Ltd (2025) Fig 1The superficial muscles of the back Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Pro Feature - Dissection Images The superficial and intermediate muscles of the back The superficial and intermediate muscles of the back You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More Print Article Rate This Article