Which layer surrounds individual nerve fibers within a nerve, forming the endoneurial sheath?

Which layer surrounds individual nerve fibers within a nerve, forming the endoneurial sheath?

• A. Perineurium
• B. Myelin
• C. Endoneurium
• D. Epineurium

Answer: (C)

The layer that surrounds each individual nerve fiber within a nerve is the endoneurium. In a peripheral nerve, each axon is wrapped by Schwann cells and a delicate connective tissue layer—the endoneurium—that sits inside the fascicle. This endoneurial sheath provides a protected microenvironment for the fiber, contains capillaries, and helps electrically and metabolically separate one fiber from its neighbors. It’s distinct from other connective tissue layers: the perineurium encases each fascicle of fibers, and the epineurium surrounds the entire nerve. Myelin covers the axon as an insulating layer produced by Schwann cells, but that myelin is not the same as the endoneurial sheath around the fiber.

The layer that surrounds each individual nerve fiber within a nerve is the endoneurium. In a peripheral nerve, each axon is wrapped by Schwann cells and a delicate connective tissue layer—the endoneurium—that sits inside the fascicle. This endoneurial sheath provides a protected microenvironment for the fiber, contains capillaries, and helps electrically and metabolically separate one fiber from its neighbors. It’s distinct from other connective tissue layers: the perineurium encases each fascicle of fibers, and the epineurium surrounds the entire nerve. Myelin covers the axon as an insulating layer produced by Schwann cells, but that myelin is not the same as the endoneurial sheath around the fiber.