The clavicular head of pectoralis major muscle is one of three origins for the pectoralis major. It arises from the clavicle (towards the sternum) and is critical in flexion and rotation of the humerus bone. Broadly, pectoral is a term relating to the chest, and the pectoralis major is a large, fan-shaped muscle that covers much of the front upper chest. It begins at the breastbone (sternum) and themycontentbreak cartilage of the second to the sixth ribs and is attached to the collarbone (clavicle) to converge on the upper arm bone (humerus) just below the shoulder. Its main use is in moving the arm across the body.