The neural crest, a two-strip tissue running lengthwise above the neural tube, develops the peripheral nervous system.

The first sign of the nervous system is the appearance of a thin strip of cells called the neural plate. The inner portion of the neural plate gives rise to the central nervous system (CNS), while the outer part becomes the peripheral nervous system (PNS). As development proceeds, the future CNS appears as a cylindrical structure called the neural tube. In contrast, the future PNS appears as two strips of tissue called the neural crest, running lengthwise above the neural tube. The sequence of stages from neural plate to neural tube and neural crest is known as neurulation. Neural crest cells from the roof plate of the neural tube migrate through the borders where they change into varied cell types, including pigment cells and the cells of the PNS.

Key Points

• The first sign of the nervous system is the appearance of a thin strip of cells along the center of the back, called the neural plate.

• The inner portion of the neural plate becomes the central nervous system (CNS), while the outer part becomes the peripheral nervous system (PNS).

• Neurulation (neural development) progresses with the formation of the neural canal, which closes to form the neural tube and neural crest.

• Neural crest cells migrate through the borders where they change into varied cell types, including pigment cells and the cells of the PNS.

Key Terms

neurulation: the process by which the beginnings of the vertebrate nervous system is formed in embryos

neural plate: a thick, flat bundle of ectoderm formed in vertebrate embryos after induction by the notochord

neural crest: a strip of ectodermal material in the early vertebrate embryo inserted between the prospective neural plate and the epidermis