Nerve · Neck

Long thoracic nerve

Nervus thoracicus longus

The long thoracic nerve has one job: it supplies serratus anterior, the muscle that holds the shoulder blade flat against the ribcage and swings it round as you reach overhead. It is formed from C5, C6 and C7 and then runs a long, exposed course straight down the outer wall of the chest on the surface of the very muscle it supplies. That exposure is its weakness — injury produces the most recognisable sign in the shoulder girdle: medial winging of the scapula, where the inner border lifts away from the ribs when you push against a wall, together with difficulty raising the arm fully overhead.