George Sánchez, BS

The pectoralis major muscle originates from multiple locations, including the costal cartilage of ribs two through six, the sternum, the medial half of the clavicle and the external oblique fascia. From this point of origin, the pectoralis major muscle divides into two muscular heads: the sternal and clavicular heads. These two muscular heads converge into a singular attachment at the humeral shaft; more specifically, at the crest of the greater tubercle and lateral lip of the intertubercular, or bicipital, groove. Nevertheless, uncertainty persists regarding the exact direction and rotation of the muscle fibers, as well as the number of tendons associated with these two muscular heads.