The L5 nerve root is one of the five lumbar nerve roots in the lower back, specifically the fifth one. It emerges from the spinal cord and is part of the lumbar plexus, which supplies nerves to the lower limbs. The L5 nerve root plays a crucial role in transmitting sensory and motor signals to and from the legs and feet. This nerve root is responsible for controlling movements in the lower leg, particularly the ability to lift the foot, known as dorsiflexion. It also provides sensation to parts of the foot, including the top of the foot and the big toe. Damage or irritation to the L5 nerve root can lead to pain, weakness, or numbness in these areas.