The scalene muscles are a group of three pairs of muscles in the lateral neck , namely the anterior scalene, middle scalene, and posterior scalene. They are innervated by the fourth, fifth, and sixth cervical spinal nerves (C4-C6).
There are actually three scalene muscles on each side of the neck that function together. They are: scalenus anterior, scalenus medius, and scalenus posterior. Sometimes there is also a scalenus minimus, but it’s not especially common.