Composition: The cord is divided into 31 segments (8 cervical, 12 thoracic, 5
lumbal, 5 sacral, and 1 coccygeal), and each segment is connected to a pair of spinal nerves by posterior (dorsal) and anterior (ventral) roots.
- Gray matter - butterfly-shaped inner substance surrounding the central canal
contains neuronal cell bodies and their
dendrites, axons, and neuroglia. Nuclei
are the functionally related groups of cell bodies.
- White matter - peripheral substance contains only myelinated and unmyelinated axons traveling to and from other
parts of the cord and to and from the brain. Tracts
are functionally related bundles of axons.