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.