Which connective tissue sheath surrounds a nerve fascicle?

Which connective tissue sheath surrounds a nerve fascicle?

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

Answer: (A)

The main idea is how nerve tissue is organized into layered connective tissue sheaths: an axon is wrapped by the endoneurium, a cluster of axons (a fascicle) is wrapped by the perineurium, and the entire nerve is wrapped by the epineurium. The sheath surrounding a nerve fascicle is the perineurium. It serves as a protective, diffusion-barrier layer that helps maintain the environment for the bundled nerve fibers. In contrast, the endoneurium surrounds individual axons within the fascicle, the epineurium encases the whole nerve, and myelin is the insulating layer around each axon produced by Schwann cells, not a sheath of the fascicle.

The main idea is how nerve tissue is organized into layered connective tissue sheaths: an axon is wrapped by the endoneurium, a cluster of axons (a fascicle) is wrapped by the perineurium, and the entire nerve is wrapped by the epineurium. The sheath surrounding a nerve fascicle is the perineurium. It serves as a protective, diffusion-barrier layer that helps maintain the environment for the bundled nerve fibers. In contrast, the endoneurium surrounds individual axons within the fascicle, the epineurium encases the whole nerve, and myelin is the insulating layer around each axon produced by Schwann cells, not a sheath of the fascicle.