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Nerve root
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<p>A nerve root is the initial segment of a <a href="/facts/Nerve/q7GsAfYV">nerve</a> leaving the <a href="/facts/Central_nervous_system/k8I6To97">central nervous system</a>. Nerve roots can be classified as: </p><ul><li><a href="/facts/Cranial_nerves/8zAVI3Ua">Cranial nerve</a> roots: the initial or proximal segment of one of the twelve pairs of cranial nerves leaving the central nervous system from the <a href="/facts/Brain_stem/lD3WQbXM">brain stem</a> or the highest levels of the <a href="/facts/Spinal_cord/XbWLr917">spinal cord</a>.</li> <li><a href="/facts/Spinal_nerve/qBQyUIKh">Spinal nerve</a> roots: the initial or proximal segment of one of the 31 pairs of spinal nerves leaving the central nervous system from the <a href="/facts/Spinal_cord/XbWLr917">spinal cord</a>. Each spinal nerve is a <a href="/facts/Mixed_nerve/2rxh9Lp1">mixed nerve</a> formed by the union of a sensory <a href="/facts/Dorsal_root/Jq7xcve6">dorsal root</a> and a motor <a href="/facts/Ventral_root/f6V4RD2G">ventral root</a>, meaning that there are 62 dorsal/ventral root pairs, and therefore 124 nerve roots in total, each of which stems from a bundle of nerve rootlets (or root filaments).</li></ul>