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The iliohypogastric nerve is one of the two cutaneous nerves of the inguinal ligament, which is a band of fibers that runs from the pelvis to the pubic area. It originates from the front branch of one of the five spinal nerves called lumber nerves, which are found between the thorax and pelvis. The iliohypogastric nerve derives part of its name from its location, the hypogastrium, which is the lowest-positioned area of the abdomen — between the navel and the pubic region. Like other nerves in the body, it provides innervation — in this case, the hypogastrium and its surrounding areas.
The origin for the iliohypogastric nerve is spinal nerve L1, which is named so because it is the topmost lumbar nerve. Sometimes the 12th thoracic nerve serves as the origin instead. This nerve is also named after its location, which is the thorax, or the region between the head and abdomen. This nerve is more commonly referred to as T12 or the subcoastal nerve.
The iliohypogastric nerve travels the psoas major muscle's lateral boundary, which is in the lumbar region. It then crosses before the quadrilateral-shaped quadratus lumborum muscle to reach the iliac crest, running behind the kidneys. Near the iliac crest, the nerve goes through the transverse abdominal muscle, or transversus abdominis. It is here, between the abdomen’s transverse muscle and internal oblique muscle, that the nerve splits into two branches of the iliohypogastric nerve — the lateral cutaneous and the anterior cutaneous.
Also known as the iliac branch because it travels above the iliac crest, the lateral cutaneous branch is the part of the iliohypogastric nerve that is distributed to the gluteal region — more specifically, the skin of the buttocks — for innervation. It is called lateral because it goes to the lateral side of the gluteal region. The anterior cutaneous branch is also known as the hypogastric branch, since it is transferred to the skin of the hypogastrium.
Of the two cutaneous nerves of the inguinal ligament, the iliohypogastric nerve is superior, meaning that it is positioned above the other. Thus, the ilioinguinal nerve is referred to as the inferior of the two branches. Like its counterpart, it originates from L1, and, occasionally, T12. Its distribution, however, is to the upper region of the scrotum’s skin in males and the labia majora in females, and to the thigh’s adjacent part. Befittingly, the site of distribution is called the anterior scrotal nerve in males and the anterior labial nerve in females.