Pectoralis Major

The Pectoralis Major is a large fan-shaped muscle with a broad origin from the clavicle and costal cartilages. It inserts laterally on the crest of the greater tubercle. The medial and lateral pectoral nerves innervate the pectoralis major muscle.

Surgical neck fractures cause medial displacement of the proximal shaft of the humerus due to the strong adduction of the pectoralis major muscle.