Copp, "EphrinA-EphA receptor interactions in mouse spinal neurulation: implications for neural fold
fusion," The International Journal of Developmental Biology, vol.
Although the cells generally emerge after neural tube closure, emigration in some species is initiated from still-open neural folds
prior to completion of neurulation, as is the case in anuran lissamphibians and mammals (for review, see Baker and Bronner-Fraser, 1997).
According to the "spherical" theory, the two originally separate embryonic discs fuse always homologously either dorsally at the closing neural folds
or ventrally at structures surrounding a common yolk sac.
At approximately day 17 of gestation, the neural plate invaginates and the lateral portions thicken, forming the neural folds
. Meningomyeloceles represent the the most important clinical examples of disordered neurulation because most affected infants survive.
As the embryo develops, the ectoderm-derived neural plate indents to produce a neural groove, which is essentially an open depression bordered by neural folds
[ILLUSTRATION FOR FIGURE 1 OMITTED].