The spinal nerves arise through numerous rootlets along the dorsal and ventral surfaces of the spinal cord. About six to eight of these rootlets combine to form a ventral root on the ventral (anterior) side of the spinal cord, and another six to eight form a dorsal root on the dorsal (posterior) side of the cord at each segment. The ventral root contains efferent (motor) fibers, and the dorsal root contains afferent (sensory) fibers. The dorsal and ventral roots join one another just lateral to the spinal cord to form the spinal nerve. The dorsal root contains a ganglion, called the dorsal root, or spinal ganglion, near where it joins the ventral root.