Origin: Posterior tubercles of transverse process of C2-C6
Insertion: First rib
Artery: Ascending cervical artery (branch of inferior thyroid artery)
Nerve: Ventral rami of the third to eighth cervical spinal nerves
Action: Elevate 1st rib, rotate the neck to the opposite side
The Scalenus medius, the largest and longest of the three Scaleni, arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae, and descending along the side of the vertebral column, is inserted by a broad attachment into the upper surface of the first rib, between the tubercle and the subclavian groove.