contributes to morphology of extends_fibers_into spinal nerve nerve root spinal cord spinal nerve root DHBA:146035120 BTO:0000883 root of spinal nerve GAID:717 spinal root NCIT:C12791 spinal neural root UBERON:0009623 MESH:D013126 FMA:14060 ZFA:0005578 The paired bundles of nerve fibers entering and leaving the spinal cord at each segment. The dorsal and ventral nerve roots join to form the mixed segmental spinal nerves. The dorsal roots are generally afferent, formed by the central projections of the spinal (dorsal root) ganglia sensory cells, and the ventral roots efferent, comprising the axons of spinal motor and autonomic preganglionic neurons. There are, however, some exceptions to this afferent/efferent rule.