Redlich-Obersteiner's Zone

The Redlich -Oberstein zone is regarded as the boundary between the central and peripheral nervous system. It is located in the area where the dorsal root ( dorsal radices ) in the dorsal horn ( Cornu posterior ) of the spinal cord (medulla spinalis) occurs. In this area, coming from the periphery, sensory ( afferent ) nerve fibers appear unmyelinated, actually their myelin sheaths are only diluted and barely perceptible.

For electron microscopic examination reveals that the actual boundary is not linear, as each axon the last Ranviersche constriction ( before entering the spinal cord) marks the transition. Up to this point the last node wrapping of the axon is still surrounded by a basement membrane and belongs to the peripheral nervous system, which now following internode has no basement membrane and marks the beginning of the central nervous system.

The basement membrane is a boundary pass through the only axons through.