Summary Scalene Origin Transverse process of C2 to C7 Insertion Anterior and medial scalene insert on first rib. Posterior scalene inserts on second rib. Action Anterior and medial scalene elevate first rib and flexes neck to same side. Posterior scalene elevates second riband flexes neck to same side. Innervation Anterior branches of the cervical spinal nerves (C3-C8) Arterial Supply Ascending cervical artery (branch of the thyrocervical trunk)