The transversus muscle is a thin sheet of muscle that lies deep to the internal oblique, and its fibers run horizontally forward. It arises from the deep surface of the lower six costal cartilages (interdigitating with the diaphragm), the lumbar fascia, the anterior two-thirds of the iliac crest, and the lateral third of the inguinal ligament. It is inserted into the xiphoid process, the linea alba, and the symphysis pubis. The lowest tendinous fibers join similar fibers from the internal oblique to form the conjoint tendon, which is fixed to the pubic crest and the pectineal line.
The posterior border of the external oblique muscle is free, while the posterior borders of the internal oblique and transversus muscles are attached to the lumbar vertebrae by the lumbar fascia.