All but one type of neuroglia (glial cells) are derived from same ectoderm that produces neurons. Most organs are from the mesoderm. There are six categories of neuroglia:
- Neurolemmocytes (Schwann cells) form myelin layers around axons in the PNS.
- Oligodendrocytes form myelin layers around axons in the CNS.
- Microglia are derived from mesoderm and remove foreign and degenerated material in the CNS.
- Astrocytes help regulate passage of molecules from blood to brain.
- Ependymal cells line brain ventricles and central canal of spinal cord
- Ganglionic gliocytes support neuron cell bodies within ganglia off the PNS.