The Iliohypogastric Nerve (n. iliohypogastricus) arises from the first lumbar nerve. It emerges from the upper part of the lateral border of the Psoas major, and crosses obliquely in front of the Quadratus lumborum to the iliac crest. It then perforates the posterior part of the Transversus abdominis, near the crest of the ilium, and divides between that muscle and the Obliquus internus abdominis into a lateral and an anterior cutaneous branch.
The lateral cutaneous branch (ramus cutaneus lateralis; iliac branch) pierces the Obliqui internus and externus immediately above the iliac crest, and is distributed to the skin of the gluteal region, behind the lateral cutaneous branch of the last thoracic nerve ; the size of this branch bears an inverse proportion to that of the lateral cutaneous branch of the last thoracic nerve.
The anterior cutaneous branch (ramus cutaneus anterior; hypogastric branch) continues onward between the Obliquus internus and Transversus. It then pierces the Obliquus internus, becomes cutaneous by perforating the aponeurosis of the Obliquus externus about 2.5 cm. above the subcutaneous inguinal ring, and is distributed to the skin of the hypogastric region.
The iliohypogastric nerve communicates with the last thoracic and ilioinguinal nerves.