Development of the Nervous System

last authored:
last reviewed:




return to top



Contributing Tissues

most of the CNS is derived from ectoderm.

return to top




Early Development

During the third week, the ectoderm thickens and clusters to form the neural plate.

Neurulation, or formation of the neural tube, is the beginning of the central nervous system and forms by day 21. Fusion first occurs cervically and extends in both directions.

By day 26, a tube forms that is closed at both ends and separate from the overlying ectoderm.


By 5 weeks, the CNS is developing from the neural tube, with the notocord acting as the beginning of the the vertebrae.


Neural Crest cells

precursors for neural and non-neural cells. These include:

the neural tube cavity is the precursor to the ventricular system of the brain. Cell migration forms three layers:




Spinal Cord Development

by 5.5 weeks, anterior and posterior differentiation of the sc is apparent. An intermediate zone is present between the dorsal (alar) plate and the ventral (basal) plate. The dorsal plate gives rise to sensory function, while the ventral plate becomes motor.

Beginnings of the dorsal root ganglion are present.

By about week 20, lower alhoa motor neurons are present




Brain Development

During the 4th week of development, there are three vesicles present: the forebrain (prosencephalon), the midbrain (mesencephalon), and the hindbrain (rhombencephalon).


During the 5th-6th week, the five vesicle stage occurs. The prosencephalon divides into the telencephalon and the diencephalon, while the rhombencephalon divides into the metencephalon an


primary structure secondary structure adult structure
prosencephalon telencephalon cerebral hemispheres
  diencephalon thalamus, hypothalamus
mesencephalon mesencephalon midbrain
rhombencephalon metencephalon pons, cerebellum
  myelencephalon medulla



return to top


Things that Go Wrong


Neural tube defects

spina bifida occulta

spina bifida cystica/aperta



encephalocele (cranium bifidum)

return to top


Resources and References

return to top