Middle Scalene:The middle scalene is the largest and longest in the Scalene group of the lateral neck muscles. It has several long, arising from the cervical spine, which converge into one large belly that inserts into the first rib.
Origin: The middle scalene originates from the posterior tubercles of the transverse processes of C2-C7,
Insertion: The middle scalene inserts into the superior surface of the 1st rib, posterior to the subclavian groove.
Function: Middle scalene acts with anterior and posterior scalene muscles. Elevation of the first rib. Ipsilateral contraction causes ipsilateral lateral flexion of the neck.
Innervation: Anterior rami of C3-C8.
Blood Supply: Muscular branches of the ascending cervical artery.