Simultaneously, derivatives of neural crest cells (cells derived from neural folds during formation of the neural tube) differentiate into neurons on each side of the neural tube and extend processes both medially and laterally (Fig. 1.35):
Medial processes pass into the posterior aspect of the neural tube.
Lateral processes pass into the differentiating regions of the adjacent dermatomyotome.
Neurons that develop from cells within the spinal cord are motor neurons and those that develop from neural crest cells are sensory neurons.