ABSTRACT
In the 5th week, the neural canal becomes diamond shaped in cross section, and a bilateral sulcus limitans separates an alar (sensory) from a basal (motor) lamina (Figure 2a). Ventricular cells in the confines of outer and inner limiting membranes spawn off an outer cell-rich intermediate zone of neuroblasts and macroglial cells (Figure 2b). The bipolar cells of the early dorsal root ganglia are sensory, and develop central axonal and peripheral dendritic processes. The axons grow into the neural tube, forming a marginal zone of fibers in the emerging spinal cord (Figures 2b and c).
