The pectoralis major has a broad origin that includes the anterior surfaces of the medial half of the clavicle, the sternum, and related costal cartilages. The muscle fibers converge to form a flat tendon, which inserts into the lateral lip of the intertubercular sulcus of the humerus.
The pectoralis major adducts, flexes, and medially rotates the arm.
The subclavius and pectoralis minor muscles underlie the pectoralis major: