the neurilemma of axons in the pns is formed by
Neurilemma Neurilemma (also known as neurolemma, sheath of Schwann, or Schwann's sheath)[1] is the outermost nucleated cytoplasmic layer of Schwann cells (also called neurilemmocytes) that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral nervous system.[2]
Myelin Myelin is a lipid-rich (fatty) substance formed in the central nervous system (CNS) by glial cells called oligodendrocytes, and in the peripheral nervous system (PNS) by Schwann cells. Myelin insulates nerve cell axons to increase the speed at which information (encoded as an electrical signal) travels from one nerve cell body to another (as in the CNS) or, for example, from a nerve cell body to a muscle (as in the PNS). The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. Rather, each myelin sheath insulates the axon over a single section and, in general, each axon comprises multiple long myelinated sections separated from each other by short gaps. Each myelin sheath is formed by the concentric wrapping of an oligodendrocyte or Schwann cell process around the axon.