In terms of the individual regions, the sternocostal head originates on the (1) anterior surface of the sternum, (2) the superior six costal cartilages, and (3) aponeurosis of the external oblique muscle, and then inserts on the bicipital groove. (strengthandconditioningresearch.com)
The sternal - costal head of the pectoralis muscle originates at the lateral manubrium, the six sternum costal cartilages and the eternal oblique aponeurosis and it inserts at the humerus. (fitnessandpower.com)