epineurium

Each peripheral nerve is surrounded by a loose connective tissue sheath, the epineurium, composed mainly of collagen and fibroblasts. Its thickness varies along the course of a nerve: it forms a substantial covering over nerve trunks and then thins to an incomplete layer around the smaller branches near their terminations. Centrally the sheath is continuous with the dura, so the outermost connective tissue investment of a peripheral nerve is continuous with the meningeal covering of the central nervous system. Peripherally it usually ends near the termination of a nerve fibre, though it may continue as the capsule of Meissner corpuscles and of a few other encapsulated endings, in which case the sheath becomes part of a sensory receptor.