Pectoralis Major

• Click here for access to the full Anatomy Glossary.
• Right click on the image for a downloadable file of this muscle.
• Use of this artwork requires proper credit to be given (Permission: Dr. Joe Muscolino. www.learnmuscles.com – art work Giovanni Rimasti)

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)

NOTES:

• The pectoralis major comprises the vast majority of the anterior axillary fold of tissue.
• There is a twist in the fibers of the sternocostal head of the pectoralis major.