The pectoralis major muscle is one of the major muscles of the upper anterior chest. Its main actions are to flex the humerus (as in doing bicep curls) and to adduct and medially rotate the humerus (i.e., to bring the arm into the side and rotate it counterclockwise.)
The nerve supply is from the lateral and medial pectoral nerves. The proximal attachment is the clavicular head, the sternocostal head, the six most superior costal (rib) cartilages, and the aponeurosis of the external oblique muscle. The distal attachment is the intertubercular groove of the humerus.
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