Origin Posterior tubercles of transverse processes of C1 - C4 vertebrae Insertion Superior part of medial border of scapula Action Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula Innervation Dorsal scapula (C5) and cervical (C3 and C4) nerves (C3, C4, C5) Arterial Supply Dorsal scapular artery