Iliohypogastric nerve

The iliohypogastric nerve, along with the ilioinguinal nerve, originates as a single trunk from the anterior ramus of the first lumbar spinal nerve (L1) within the lumbar plexus, which is embedded in the psoas major muscle. Upon reaching the lateral border of the psoas major, this trunk bifurcates into the iliohypogastric and ilioinguinal nerves.

The iliohypogastric nerve takes an oblique path as it crosses anterior to the quadratus lumborum muscle. It then pierces the transversus abdominis muscle and travels forward along the abdominal wall, running within the plane between the transversus abdominis and internal oblique muscles.

At a point just superior to the iliac crest, the iliohypogastric nerve divides into two branches:

The lateral cutaneous branch:

This branch pierces the internal oblique muscle and the external oblique aponeurosis, providing sensory innervation to the skin over the posterolateral gluteal region.

The anterior cutaneous branch:

This branch courses anteriorly and medially, staying between the transversus abdominis and internal oblique muscles. Along the abdominal wall, it supplies motor innervation to both the transversus abdominis and internal oblique muscles. As it approaches the anterior superior iliac spine, just medial to this landmark, the anterior cutaneous branch pierces the internal oblique muscle and the external oblique aponeurosis to emerge as a cutaneous nerve. It then provides sensory innervation to the skin over the lower abdominal wall, particularly in the hypogastric or pubic region.