Which connective tissue layer surrounds a nerve fascicle?

Which connective tissue layer surrounds a nerve fascicle?

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

Answer: (C)

The key idea is how a peripheral nerve is organized into layers around its inner units. Inside a nerve, axons bundle together into fascicles. Each individual axon is wrapped by the endoneurium, but the fascicle itself is surrounded by the perineurium. The perineurium acts as a protective, barrier-like sheath that provides mechanical support and helps regulate the internal environment of the fascicle, contributing to the blood-nerve barrier. The entire nerve, in turn, is encased by the epineurium. The dura is not part of a peripheral nerve; it’s a meningeal layer surrounding the brain and spinal cord. So the layer that surrounds a nerve fascicle is the perineurium.

The key idea is how a peripheral nerve is organized into layers around its inner units. Inside a nerve, axons bundle together into fascicles. Each individual axon is wrapped by the endoneurium, but the fascicle itself is surrounded by the perineurium. The perineurium acts as a protective, barrier-like sheath that provides mechanical support and helps regulate the internal environment of the fascicle, contributing to the blood-nerve barrier. The entire nerve, in turn, is encased by the epineurium. The dura is not part of a peripheral nerve; it’s a meningeal layer surrounding the brain and spinal cord. So the layer that surrounds a nerve fascicle is the perineurium.