Lumbar Plexus: The lumbar plexus is a nerve network in the lumbar region of the body. It is formed by the first four lumbar nerves (L1-L4) and contributions of the subcostal nerve (T12). The nerves of the lumbar plexus cross in front of the hip joint and chiefly support the anterior part of the thigh.
It is located in the lumbar region, within the psoas major muscle and anterior to the transverse processes of the lumbar vertebrae.
The anterior rami of the L1-L4 spinal roots split into several cords. These cords then connect together to form the six major peripheral nerves of the lumbar plexus.
Lateral Cutaneous Nerve of the Thigh
The iliohypogastric nerve is the first main branch of the lumbar plexus. It moves to the iliac crest, over the quadratus lumborum muscle of the posterior abdominal wall. It next penetrates the transversus abdominis and divides into its terminal branches.
Roots: L1, T12
Motor Functions: Motor supplies of the internal oblique and transversus abdominis.
Sensory Functions: Innervates the posterolateral gluteal skin in the pubic region
The ilioinguinal nerve has the same anatomical course of the iliohypogastric nerve.
Motor Functions: Supplies the internal oblique and transversus abdominis.
Sensory Functions: Supplies the skin on the upper middle thigh. In the case of males, it also supplies the skin over the root of the penis and anterior scrotum. In the case of females, it supplies the skin over mons pubis and labia majora.
After passing the psoas major muscle, the genitofemoral nerve divides into a genital branch and a femoral branch.
Roots: L1, L2.
Motor Functions: The genital branch supplies the cremasteric muscle.
Sensory Functions: The genital branch innervates the skin of the anterior scrotum (in the case of males) or the skin over mons pubis and labia majora (in the case of females). The femoral branch innervates the skin on the upper anterior thigh.
This nerve has an only sensory function. It penetrates the thigh at the lateral aspect of the inguinal ligament, where it supplies cutaneous innervation to the skin.
Roots: L2, L3
Motor Functions: None.
Sensory Functions: Supplies the anterior and lateral thigh down to the level of the knee.
Roots: L2, L3, L4.
Sensory Functions: Supplies the skin over the medial thigh.
Roots: L2, L3, L4.
Sensory Functions: Supplies the skin on the anterior thigh and the medial leg.