Shaping and bending of the avian neuroepithelium: morphometric analyses.

Changes in the size and shape of the neuroepithelium were measured from serial transverse sections of 30 plastic-embedded chick embryos at stages 4-11. The neural plate folds into a neural tube during this period. Changes in volume, length, apical and basal widths, apical and basal surface areas, and thickness of the neuroepithelium were measured and correlated with the amount of folding that had occurred. These measurements were made to provide data for comparison with those available from other systems, to gain insight into the mechanisms of shaping and bending of the neuroepithelium, and to obtain normal parameters for eventual comparison with those obtained from embryos with induced neural tube defects. During stages 4-11, the volume, length, apical and basal surface areas, and lateral thickness of the neuroepithelium increase, whereas apical and basal widths and median thickness of the neuroepithelium decrease. Models are presented to demonstrate the effects of possible changes in neuroepithelial cell number, position, and size on the shaping of the neural plate.