The scalene muscles are lateral vertebral muscles that begin at the first and second ribs and pass up into the sides of the neck. There are three of these muscles: the scalenus anterior, scalenus medius, and scalenus posterior.
- When the neck is fixed, the scalenus anterior muscle elevates the first rib to aid in breathing; or when the rib is fixed, bends the neck forward and sideways and rotates it to the opposite side.
- The scalenus medius is similar to the scalenus anterior and raises the first rib from above or bends to slightly rotate the neck from below.
- The scalenus posterior raises the second rib or bends and slightly rotates the neck. This muscle may be absent or may extend to the third rib.
When the scalene muscles are fixed from above, they elevate the first and second ribs to become respiratory muscles for breathing. Acting from below, they bend the spinal column to the same side or, if muscles act on both sides, the spinal column is slightly flexed.