rectus abdominis muscle

Running vertically on each side of the anterior abdominal wall, rectus abdominis is a paired muscle whose two parallel sets are separated by a midline band of connective tissue, the linea alba. Each muscle extends from the pubic symphysis and pubic crest below to the xiphoid process and the fifth to seventh costal cartilages above, and is contained within the rectus sheath. Its belly is usually crossed by three fibrous bands, the tendinous inscriptions, which divide the vertical muscle into a series of segments. That segmentation, together with the enclosing sheath and the midline raphe, is what gives the anterior abdominal wall its characteristic surface relief. It is classified here as an anterior abdominal wall muscle.