The document describes the anatomy of the anterolateral abdominal muscles and rectus sheath in three sections. In the area above the costal margin, the rectus sheath has an external oblique aponeurosis anterior wall and deficient posterior wall. Between the costal margin and arcuate line, the rectus sheath has an external oblique aponeurosis and internal oblique muscle anterior walls, and an internal oblique and transversus muscle posterior wall.