The ilioinguinal nerve closely follows the iliohypogastric nerve on the quadratus lumborum, but then passes below it to run at the level of the iliac crest.
Laterally, it blends with the middle layer at the lateral border of the quadratus lumborum.
In the lateral tract, the iliocostalis lumborum and longissimus thoracis originates on the back of the sacrum and the posterior part of the iliac crest.
The main muscles involved include the transversus abdominis, the internal and external obliques, the quadratus lumborum and the diaphragm.
The lumbar vessels travel through the erector spinae muscles or between the erector spinae muscle and quadratus lumborum muscle.
It forms an arch over the quadratus lumborum muscle.
It emerges from the lateral border of the psoas major just inferior to the iliohypogastric, and passes obliquely across the quadratus lumborum and iliacus.
Laterally, it blends with the anterior layer at the lateral border of quadratus lumborum.
