Which sheath surrounds a single axon within a nerve, forming the endoneurial sheath?

Which sheath surrounds a single axon within a nerve, forming the endoneurial sheath?

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

Answer: (C)

The innermost protective layer around each individual nerve fiber is the endoneurium. This delicate connective tissue surrounds a single axon (and its myelin segments), keeping it separate from neighboring fibers and providing a small space with capillaries that support the fiber. Surrounding a group of axons, a tougher layer called the perineurium wraps a fascicle, while the entire nerve is enclosed by the epineurium. Myelin is the insulating sheath formed by Schwann cells along the axon, not the endoneurial sheath itself.

The innermost protective layer around each individual nerve fiber is the endoneurium. This delicate connective tissue surrounds a single axon (and its myelin segments), keeping it separate from neighboring fibers and providing a small space with capillaries that support the fiber. Surrounding a group of axons, a tougher layer called the perineurium wraps a fascicle, while the entire nerve is enclosed by the epineurium. Myelin is the insulating sheath formed by Schwann cells along the axon, not the endoneurial sheath itself.