Anterior scalene m.

Lies deep to the SCM in the neck.  Runs from the transverse processes of C3 - C6 to the first rib.  Innervated by the ventral rami of C5 and C6.  Elevates the first rib and rotates the neck.  The phrenic n. typically runs along the anterior surface of the anterior scalene m., and the roots of the brachial plexus and the subclavian a. and v. pass posterior to the muscle.