The fibers of the transversus abdominis, the innermost of the three flat abdominal muscles, run more or less transversally, except for the inferior ones, which run parallel to those of the internal oblique. This transverse, circumferential orientation is ideal for compressing the abdominal contents, increasing intra-abdominal pressure. The fibers of the transversus abdominis muscle also end in an aponeurosis, which contributes to the formation of the rectus sheath.

Between the internal oblique and the transversus abdominis muscles is a neurovascular plane, which corresponds with a similar plane in the intercostal spaces. In both regions, the plane lies between the middle and deepest layers of muscle. The neurovascular plane of the anterolateral abdominal wall contains the nerves and arteries supplying the anterolateral abdominal wall. In the anterior part of the abdominal wall, the nerves and vessels leave the neurovascular plane and lie mostly in the subcutaneous tissue.