The long thoracic nerve is a branch of the brachial plexus given off above the clavicle. It lies along the medial wall of the axilla. It arises by three roots. The upper two roots spring from the fifth and sixth cervical nerves and the lower one springs from the seventh cervical nerve. The upper two roots pierce the scalenus medius muscle, while the lower root passes in front of it. Usually the two portions of the nerve, formed by the union of the upper two roots and the lower root, pass into the axilla separately behind the brachial plexus and vessels. They then join to form the common trunk which supplies the serratus anterior muscle, upon whose lateral surface the nerve lays.

Nervus thoracicus longus

Nerf thoracique long