Development Embryonic Development of the CNS I. Development A. Embryonic layers 1.
Embryonic disc consists of ectoderm, mesoderm and endoderm a.
Occurs roughly between days 18 and 21 of embryonic development 2. Closed neural tube consists of single layer of pseudostratified columnar epithelium, ow considered to be neuroepithelium a. Dorsal and ventral regions of tube thin to form roof plate and floor plate 3. Neural crest cells come to lie laterally adjacent to tube 4. This stage reached at about end of fourth week of development 5.