The lumbar plexus is a nerve plexus in the body's lumbar region, which is formed by the ventral branches of the first to the fourth upper lumbar nerves, L1-L4, with the last thoracic nerve or T12 usually supplementing the first lumbar level by a twig. The loops of communication between the first three lumbar levels and the greater portion of the fourth lumbar nerve form the lumbar plexus. The first lumbar nerve, or L1, divides into an upper and lower branch. The upper and bigger branch splits into the ilioingual and iliohypogastric nerves. It is the lower branch that unites with the second lumbar nerve, or L2. The remainder of L2, together with L3 and L4, splits into ventral and dorsal divisions. The nervous lumbar plexus of the spine is embedded in the muscle psoas major, passing in front of the hip joint. Together with the sacral plexus they give autonomic, motor, and sensory fibers to the lower extremities and to the body's gluteal and inguinal regions.
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In Depth: Lumbar plexus