Third Lumbar Nerve (Right)

Origin

The third lumbar nerve originates in, or just lateral, to the intervertebral foramen inferior to the third lumbar vertebra. Here, the anterior and posterior roots combine to form the first lumbar nerve proper.

Course

The third lumbar nerve gives off a posterior ramus, that runs to the epaxial musculature and skin of the lower back, and an anterior ramus, that runs inferior and laterally to the lumbar plexus.

Branches

The third lumbar nerve gives off a posterior ramus and contributes to three branches from the anterior ramus. These are part of the lumbar plexus and also receive contributing fibers from other lumbar levels. These include the lateral femoral cutaneous (or lateral cutaneous nerve of thigh), femoral, and obturator nerves.

Supplied Structures

The posterior ramus of the third lumbar nerve supplies the epaxial muscles of the lumbar region, including erector spinae and transversospinal muscles. In addition to cutaneous innervation of the skin over the lower back.

The anterior ramus of the third lumbar nerve contributes to the lumbar plexus and the following nerves and their targets.

—Small branches innervate the iliopsoas muscle.

—The lateral femoral cutaneous nerve contributes to both the second and third lumbar nerves and is only sensory. It innervates the anterior and lateral thigh from the inguinal ligament down to the knee.

—The femoral nerve arises from the second, third, and fourth lumbar nerves. It innervates psoas, iliacus, pectineus, sartorius, and quadriceps muscles (rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis). Sensory innervation of the femoral region is to the anterior and medial thigh.

—The obturator nerve arises from the second, third, and fourth lumbar nerves. It innervates the adductor muscles (gracilis, obturator externus, adductor longus, adductor brevis, and adductor magnus muscles). Sensory innervation of the obturator nerve is received from the skin of the medial thigh.