E-Figure 14-1.

Neurogenesis of the Central Nervous System (CNS) and Peripheral Nervous System (PNS) in the Developing Embryo.

Neuroectoderm differentiates from ectoderm and forms the neural plate. The neural plate gives rise to neural crest cells and the neural tube, which in turn differentiate into PNS (spinal ganglion, peripheral nerves) and CNS (brain and spinal cord), respectively. The notochord eventually regresses, and portions remain as the nucleus pulposus of intervertebral disks.

(Courtesy Dr. A.D. Miller, College of Veterinary Medicine, Cornell University; and Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois.)