On each side, the scalenus anterior muscle is one of the muscles within the root of the neck. It takes origin from the anterior tubercles of the transverse processes of the third to the sixth cervical vertebrae. Hence, there are four slips of muscle which merge as they pass inferiorly and slightly laterally to insert into the scalene tubercle on the inner aspect of the superior surface of the first rib.
Scalenus anterior is innervated by the anterior rami of C5 and C6.
Its actions are:
- assistance in stabilising the first rib
- flexion and/or rotation of the neck if the first rib is fixed by other muscles
Scalenus anterior acts as an important landmark for other structures within the root of the neck. The phrenic nerve and ascending cervical artery cross its anterior surface beneath the prevertebral fascia.