Corpus: Posterior scalene muscle
from Latin: scala - staircase
1. Definition
The posterior scalene muscle is a skeletal muscle that is part of the neck musculature.
2. Course
The posterior scalene muscle originates from the posterior tubercles of the transverse processes of the 5th and 6th cervical vertebrae. It inserts on the outer surface of the 2nd rib, and occasionally also on the 3rd rib.
3. Innervation
The posterior scalene muscle is innervated by the anterior branches of the spinal nerves from spinal cord segments C7 and C8.
4. Function
When contracting bilaterally, the posterior scalene muscle elevates the 2nd and 3rd ribs, thereby increasing thoracic volume and acting primarily as an accessory respiratory muscle. When contracted unilaterally, it can slightly tilt the cervical spine to the same side.