The Redlich–Obersteiner's zone, also known as the root entry zone, is a boundary between the central nervous system (CNS) and the peripheral nervous system (PNS). The Redlich–Obersteiner's zone is located at the point of entry of either between cranial nerves and the brain or spinal nerves and the spinal cord.
This zone serves as a demarcation point between the CNS and PNS, specifically where cranial nerves meet the brain or spinal nerves interface with the spinal cord.