Genitofemoral nerve

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The genitofemoral nerve is a branch of the lumbar plexus arising within the substance of the psoas major muscle from the union of anterior rami of L1 and L2 spinal nerves. The nerve descends in the retroperitoneum to give off genital and femoral terminal branches supplying the skin over the anterior scrotum or labia majora and lateral femoral triangle respectively.

Gross anatomy

Origin

The genitofemoral nerve is formed in the substance of the psoas major muscle by the union of branches from the anterior rami of L1 and L2 spinal nerves of the lumbar plexus.

Course

The nerve passes downwards within the substance of the psoas major muscle, eventually emerging on the muscle's anterior surface, and possibly the psoas minor muscle when present, deep to the psoas fascia.

It descends in the retroperitoneum on the psoas major muscle passing on the left deep to the left ureter and gonadal vessels, left colic artery and the inferior mesenteric vein. On the right the nerve passes deep to the right ureter and gonadal vessels and the ileocolic artery and vein.

Just above the inguinal ligament both left and right genitofemoral nerves perforate the psoas fascia and divide in to genital and femoral branches.

Branches and supply

The genitofemoral nerve divides into genital and femoral branches just above the inguinal ligament:

  • genital branch, also known as the external spermatic nerve, enters the inguinal canal through the deep inguinal ring
    • in men it accompanies the spermatic cord and descends supplying motor fibers to the cremaster and dartos muscles and sensory fibers to the spermatic fasciae and tunica vaginalis of the testis. The nerve also provides cutaneous sensation to upper anterior portion of the scrotum
    • in women the nerve accompanies the round ligament of the uterus and provides innervation to the skin of the mons pubis and labium majus
  • femoral (crural) branch, also known as the lumboinguinal nerve, descends lateral to the external iliac artery and passes beneath the inguinal ligament entering the femoral sheath anterolateral to the common femoral artery. The nerve pierces the femoral sheath and fascia lata to supply the skin of the groin below the mid-part of the inguinal ligament (the femoral triangle)
Relations

At its origin, the genitofemoral nerve is found on the anterior surface of the psoas major muscle from which it emerges. The nerve then courses in the retroperitoneum and lies posterior to the ureter, gonadal vessels and abdominal vessels. The nerve bifurcates above the inguinal ligament with the femoral branch passing under the ligament on the lateral aspect of the external iliac artery entering the femoral sheath lateral to the femoral artery. The genital branch passes through the deep inguinal ring along the inguinal canal accompanying the spermatic cord in men or the round ligament of the uterus in women.

Variant anatomy

Almost 50% of genitofemoral nerves examined in cadaveric studies demonstrated an anatomical variation :

  • 20% of nerves bifurcate prematurely at the upper portion (rather than the mid-portion) of the anterior surface of the psoas major muscle
  • occasionally the genital and femoral branches do not merge into a common trunk within the substance of the psoas muscle and remain as distinct nerves as they travel into the pelvis