The lateral edges of the neural folds grow medially and unite in the midline to form the neural tube which then separates from the ectoderm. Fusion begins in the cervical region on the 21st day and proceeds in both directions until the entire neural plate becomes the neural tube.

Cells from the margins of the neural tube detach from the ectodermal neural folds to form clusters of neural crest cells. These dorsally located cells migrate peripherally to become sensory ganglia of the cranial and spinal nerves, autonomic and enteric ganglia, Schwann cells, melanocytes, adrenal chromaffin cells, and the pia/arachnoid membranes (dura develops from mesoderm)  
 

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