Anterior view of the right pectoralis major. The deltoid is ghosted in. Permission Joseph E. Muscolino.
The pectoralis major is composed of two heads: sternocostal head and clavicular head.
ATTACHMENTS:
- The pectoralis major attaches from the medial clavicle, sternum, and the costal cartilages of ribs #1-7 to the lateral lip of the bicipital groove of the humerus
ACTIONS:
- Adducts the arm at the glenohumeral joint (entire muscle)
- Medially rotates the arm at the glenohumeral joint (entire muscle)
- Flexes the arm at the glenohumeral joint (clavicular head)
- Extends the arm at the glenohumeral joint (sternocostal head – from a position that is flexed beyond anatomic position)
- Horizontally flexes the arm at the glenohumeral joint (entire muscle)
- Protracts the shoulder girdle (acting through the humeral attachment) at the scapulocostal joint and sternoclavicular joints (entire muscle)
TRIVIA NOTE:
- The pectoralis major comprises the vast majority of the anterior axillary fold of tissue.