The spinal cord is a white cord 1 centimeter in diameter and 50 centimeters long, made up of neurons and glial cells. It has two bulges corresponding to the emergence of the limbs and ends in a point at the second lumbar vertebra. The spinal nerves, which are directly connected to the spinal cord, are 31 pairs (left and right), each nerve having two roots: the posterior or sensitive root and the anterior or motor root. All spinal nerves are therefore mixed: motor and sensory.