Scalenus anterior

The Scalenus anterior (Scalenus anticus), also known as anterior scalene muscle, lies deeply at the side of the neck, behind the Sternocleidomastoideus.

It arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebræ, and descending, almost vertically, is inserted by a narrow, flat tendon into the scalene tubercle on the inner border of the first rib, and into the ridge on the upper surface of the rib in front of the subclavian groove.