Extending from the fourth ventricle down to the conus medullaris, the central canal of the spinal cord is a very narrow CSF space bordered on all sides by a single layer of columnar ependymal cells. Recall that the human central nervous system first develops in utero in a process known as neurulation, and during the fourth week of development, the caudal aspects of the neural plate and neural tube fold in on themselves and zipper shut, forming a neural canal which will eventually become the central canal. The neural tube, a single layer of columnar neuroepithelial cells, then differentiates into all neurons, oligodendroglia, and astroglia of the spinal cord before differentiating into that one layer of columnar cells that lines the central canal.