The abdominal head of the pectoralis major muscle is one of three origins for the pectoralis major. It arises from the fascia of the external oblique muscle. 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 the cartilage of the second to the sixth ribs and is Continue Scrolling To Read More Below...