The lumbar plexus is a network of nerves located in the lower back, specifically within the lumbar region of the spine. It is formed by the anterior rami of the first four lumbar nerves, labeled as L1, L2, L3, and L4. This plexus is responsible for supplying motor and sensory innervation to the lower abdomen, pelvis, and parts of the lower limbs. Key nerves that branch from the lumbar plexus include the femoral nerve and the obturator nerve. The lumbar plexus plays a crucial role in movements such as hip flexion and knee extension, as well as providing sensation to the skin of the thigh and parts of the leg.