The tissue in the image is which of the following?

• A. Peripheral nerve
• B. Spinal cord
• C. Brain
• D. Muscle

Answer: (A)

When identifying this tissue, look for organized bundles of nerve fibers wrapped in protective connective tissue. A peripheral nerve shows fascicles of axons, each wrapped by a thin endoneurial layer, with groups of these axons bundled together by a perineurial sheath, and the entire nerve surrounded by an epineurium. The individual fibers usually appear as round or oval units with a clear myelin sheath, reflecting Schwann cell activity. This combination of fascicles with the surrounding connective tissue layers and numerous myelinated fibers is characteristic of a peripheral nerve.

In contrast, brain tissue would display neuronal cell bodies, glial cells, and layered gray and white matter without the distinct fascicular nerve architecture. Spinal cord tissue would show a different organization with gray matter horns and white-matter tracts rather than peripheral nerve fascicles. Muscle would reveal striated fibers with sarcomeres and peripheral nuclei, not the bundled axons with nerve sheathes seen here.