The component of the central nervous system continuous with the brain stem, and within the protective vertebral column, that extends down the spine, receiving sensory and visceral input, and containing the neurones that connect to muscles. It contains both tray and white matter (the latter consisting of ascending and descending white fibers) and has 31 pairs of spinal nerves attached to it. In the adult human, there are 1 billion neurons in the spinal cord, which is divided into 4 levels: cervical (8 segments), thoracic (12 segments), lumbar (5 segments) and sacral (5 segments), plus one coccygeal segment.
See Brachial plexus, Cell migration, Central nervous system (CNS), Corticopspinal tract, Dorsal commissural interneurons, Dorsal roots, Dorsal root ganglia (DRG), Encephalitis, Extrapyramidal system, Gray matter, Locus coeruleus (or ceruleus), Lumbosacral plexus, Medulla oblongata, Meninges, Orbitofrontal cortex, Psoas muscle, Ventral roots, White matter