Posterior scalene m

The posterior scalene is the most posterior and the deepest of the 3 scalene muscles.  It attaches to the transverse processes of the lower cervical vertebrae superiorly, and to the second rib inferiorly.  Its innervation is by branches of ventral rami of lower cervical spinal nn., and it acts to raise the second rib or tilt the neck to the side.  Sometimes the posterior scalene is not separable from the middle scalene.