The three scalene muscles (the scalenus posticus, the scalenus medius, and the scalenus anticus) work together to aid in breathing. As we inhale, they lift the first and second |rib|. They also bend the spinal column to one side or the other. The scalenus posticus is the smallest of the three muscles, originating from the lower two or three cervical (neck) |vertebrae| and descends to insert into the second |rib|. The scalenus medius is the largest and longest of the three muscles. It originates from the lower six |cervical vertebrae| and is inserted into the first |rib|. The scalenus anticus lies deep at the side of the neck, behind the sternomastoid. It originates from the third, fourth, fifth, and sixth |cervical vertebrae| and descends to the first |rib|. It also separates the subclavien |artery| and |vein|.
