The abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the posterior (back), lateral (sides) and anterior (front) walls. There is a common set of layers covering and forming all the walls: the deepest being the extraperitoneal fat, the parietal peritoneum, and a layer of fascia which has different names over where it covers (eg transversalis, psoas fascia). Superficial to these, but not present in the posterior wall are the three layers of muscle, the transversus abdominis (transverse abdominal muscle), the internal (obliquus internus) and the external oblique (obliquus externus). [ http://en.wikipedia.org/wiki/Abdominal_wall ]