Each spinal nerve stem (31 - 33 pairs) divides into a front and a hind root as it passes into the vertebral canal.
The nerve fibers in the front root convey outward nerve signals, primarily from nerve cells in the front horn of the spinal cord.
The nerve fibers in the hind root convey inward nerve signals - information from various sensory organs - to nerve cells in the spinal cord and in the medulla.