The rectus sheath is made up of two laminas, which are known as the posterior sheath and the anterior sheath. The sheaths comprise aponeurotic fibers of the transversus abdominis, internal abdominal oblique and external abdominal oblique, which are muscles of the abdomen. The convergence of these muscles takes place at the linea alba. The composition of the posterior sheath and the anterior sheath differs from one abdominal wall to another. The anterior sheath consists of the aponeurotic fibers of the EAO over the coastal margins. The posterior sheath consists of the aponeurotic fibers of the IAO and the transversus abdominis. The posterior sheath is absent benath the arcuate line, but the anterior sheath is present here as a combination of the aponeurotic fibers of all three muscles of the abdomen. In the lateral side of the rectus sheath, the aponeurotic fibers of the internal abdominal oblique segregate into two lamellae. The one on the front, goes to the aponeurosis of the external oblique. The one from behind goes to the aponeurosis of the transversus, finally joining with the aponeurosis of the external abdominal oblique.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Rectus sheath