RECTUS ABDOMINIS
This is a medial superficial abdominal muscle extending from the pubis to the rib cage. Its origins are the pubic crest and pubic symphysis. It inserts on the xiphoid process and costal cartilages of the fifth through seventh ribs. It acts to flex the vertebral column (standing you bow, lying down you do a sit up). We use it to increase pressure on internal organs during defecation, urination and labor. It also helps to depress the rib cage during forced expiration.