What is "scalene muscles"

Scalene \Sca*lene"\, a. [L. scalenus, Gr. ?: cf. F. scal[`e]ne.]

1. (Geom.)

   1. Having the sides and angles unequal; -- said of a triangle.

   2. Having the axis inclined to the base, as a cone.

2. (Anat.)

   1. Designating several triangular muscles called scalene muscles.

   2. Of or pertaining to the scalene muscles.

      Scalene muscles (Anat.), a group of muscles, usually three on each side in man, extending from the cervical vertebr[ae] to the first and second ribs.

The scalene muscles (from Greek σκαληνός, or skalenos, meaning uneven as the pairs are all of differing length) 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).

A fourth muscle, the scalenus minimus (Sibson's muscle), is sometimes present behind the lower portion of the anterior scalene.