The spinal cord is formed by a cord of nervous tissue more than 16 inches (40 cm) in length located in the vertebral canal, inside the spinal column. It spans from the spinal bulb to the second lumbar vertebra and is extended by a collection of nervous fibers, the cauda equina. Composed of motor and sensory neurons, the spinal cord ensures the transmission of messages between the spinal nerves and the brain, in addition to being a reflex center.