What is the spinal cord? Of which elements is the spinal cord constituted?

The spinal cord is the dorsal neural cord of vertebrates. It is the kind of the central nervous system that continues in the trunk to facilitate the nervous integration of the whole body.

The spinal cord is made of groups of neurons situated in its central portion forming the gray matter and of axon fibers in its exterior portion forming the white matter. Neural bundles connect to both lateral sides of the spinal cord segments to form the dorsal and ventral spinal roots that join to form the spinal nerves. The dorsal spinal roots show a ganglion with neurons that receive sensory information; the ventral spinal roots contain motor fibers. Thus the dorsal roots are sensory roots and the ventral roots are motor roots.