origin: anterior tubercles of the transverse process of the 2nd to 6th cervical vertebrae;
insertion: scalene tubercles on anterior superior surface of the 1st rib;
action:
- acting unilaterally, flexes and rotates cervicals and raises first rib;
- when acting bilaterally, flexes the neck;
nerve supply: anterior branches,
C5,
C6,
C7,
C8;
synergists: sternocleidmastoid,
scalenus medius and
scalenus posterior longus capitis, longus coli, suprahyoid, infrahyoid and the platysma;
