A Schwann cell is a glial cell of the peripheral nervous system that ensheaths axons. A myelinating Schwann cell wraps its cell membrane repeatedly around one segment of one axon, producing myelin. Adjacent Schwann cells leave a node of Ranvier between their sheaths, supporting saltatory conduction.[ref]
Anatomy and Physiology 2e by J. Gordon Betts and others. Section 12.2, Glial Cells of the PNS and Myelin
Other Schwann cells support small axons without building thick myelin sheaths. Thus being associated with a Schwann cell does not imply that a peripheral fibre is myelinated. The one-segment arrangement also differs from an oligodendrocyte, whose processes can myelinate parts of several central axons.
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