The genitofemoral nerve is a branch of the lumbar plexus, one of three components of the larger lumbosacral plexus (a network of intersecting nerves in the lower vertebral column).
Running from this source, it pierces the front surface of the psoas major — the muscle stabilizing the spine that controls rotation of the hips. At this point, it splits into its two eponymous branches (or rami): the genital ramus and the femoral ramus.
In women, the genital ramus terminates in sensory branches that supply the labia majora (part of the external genital organs). In men, the branch constitutes part of the spermatic cord and acts additionally as a motor for the cremasteric reflex. The cremaster is a muscle that elevates and lowers the testes. Sensory fibers in the upper male thigh respond to gentle touch, stimulating the motor fibers of the genital branch of the genitofemoral nerve and causing the cremaster to contract, raising the testes on the same side.
The function of the femoral branch of the genitofemoral nerve is exclusively for sensory perception in both genders. It connects to the area of skin below the inguinal ligament, which extends from the hip to the pubic bone in the groin.