Internal structures

Differentiation of the wall of the neural tube

The wall of the neural tube consists of a layer of neuro-epithelial cells whose processes stretch from the external membrane (pia mater or mesenchymal surface) to the internal membrane (ventricular surface). The cells undergo the cell cycle. Mitosis itself occurs on the ventricular surface. The position of the cellular nuclei then changes according to the phase of the cell cycle. After mitosis, the nucleus of the cell moves towards the mesenchymal surface where, after the interphase (G1 phase or postmitotic gap), it synthesizes DNA (phase of synthesis). It then migrates again towards the ventricular surface, becomes rounder in shape and enters a short interphase (G2 phase or premitotic gap). The apical process of the cell retracts and the cell divides (M or mitotic phase). The plane of division (equatorial plate) during the early developmental period is generally perpendicular to the ventricular surface. In this way, the two daughter cells remain on the ventricular surface and re-enter the cell cycle.