In this chapter, the author combines the established views of the
microstructure of the ulnar nerve as an example of a singe peripheral nerve, with some
newer concepts that have emerged only recently. The position and importance of the
circumneural (paraneural) sheath and subcircumneural (subparaneural) space are
discussed, as well as the other membranes and compartments surrounding this
peripheral nerve, namely, the endoneurium, perineurium, epineurium, and epimysium.
The subepimyseal space is discussed in the context of peripheral nerve block.
Keywords: Acute pain medicine, Axon, Circumneural sheath, Continuous peripheral
nerve block, Endoneurium, Epimysium, Fascia, Fascicles, Gliding apparatus,
Microanatomy, Nerve axon, Paraneural sheath, Perineurium Epineurium, Peripheral
nerve block, Regional anesthesia, Single peripheral nerve, Subcircumneural space,
Subepimyseal space, Subparaneural space, Ulnar nerve, Ultrastructure.
