abdominal muscles, the muscles between the thorax and the pelvis supporting the abdominal wall. The lateral parts of the wall are formed by the transverse abdominis, the internal oblique, and the external oblique. Anteriorly, on each side, a segmented muscle, the rectus abdominis, spans the distance between the inferior thoracic wall and the pelvis. Other muscles supporting the posterior aspect of the wall are the quadratus lumborum, the psoas major, and the iliacus.
