A cadaveric study of the serratus anterior muscle and the long thoracic nerve

The anatomy and function of the serratus anterior muscle and the long thoracic nerve have not been fully elucidated. The purposes of this investigation were (1) to clarify which nerve roots of the cervical spine supply each part of the muscle and contribute to the long thoracic nerve and (2) to investigate the anatomy of the 3 parts of the muscle to understand the function of each part. We collected specimens from 70 dissections of 35 cadavers (11 men and 24 women). The serratus anterior muscle consisted of the upper, middle, and lower parts. The upper part was supplied mainly by the C5 nerve root, and the C4, C6, or C7 nerve roots also had multiple branches in 64 of 70 dissections. The long thoracic nerve, consisting of the C6 and C7 nerve roots, innervated the middle and lower parts. The upper part traversed in a posterior direction compared with the middle or lower part. The upper part of the muscle, which is supplied from multiple nerve roots and runs in a posterior direction, may stabilize the rotational motion of the scapula on the thorax in shoulder elevation. The middle part provides the scapular abduction, and the lower part contributes to upward rotation, abduction, and posterior tilting.