Anatomy - Pectoralis Major

Pectoralis Major - Action (Lower fibers, sternal head)

internal rotation, horizontal adduction, adduction and extension of the glenohumeral joint from a flexed position to the anatomical position.

Pectoralis Major - Action (Upper fibers, clavicular head)

internal rotation, horizontal adduction, flexion up to about 60 degrees, abduction (once the arm is abducted 90 degrees, the upper fibers assist in further abduction), and the adduction (with the arm below 90 degrees of abduction) of the glenohumeral joint.

Pectoralis Major - Insertion

Flat tendon 2 or 3 inches wide to the lateral lip of the intertubercular groove of the humerus.

Pectoralis Major - Origin

Upper fibers (clavicular head)- medial half of the anterior surface of the clavicle. Lower fibers (Sternal head)- anterior surface of the costal cartilage of the first six ribs, and adjacent portion of the sternum.

Pectoralis Major - Innervation

Upper fibers- lateral pectoral nerve (C5-C7). Lower fibers- medial pectoral nerve (C8, T1)