Which connective tissue layer directly surrounds individual axons in a nerve?

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

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the structure of a nerve. A nerve is composed of multiple axons bundled together, and these axons are surrounded by different connective tissue layers for protection and organization.
2. Step 2: Learn the hierarchy of connective tissue layers in a nerve. The epineurium surrounds the entire nerve, the perineurium surrounds bundles of axons (fascicles), and the endoneurium surrounds individual axons.
3. Step 3: Differentiate between the connective tissue layers. The endoneurium is the innermost layer that directly surrounds each axon, providing support and insulation. The perineurium is a middle layer that groups axons into fascicles, and the epineurium is the outermost layer that encases the entire nerve.
4. Step 4: Clarify the role of the myelin sheath. The myelin sheath is not a connective tissue layer but a fatty substance produced by Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system) that insulates axons to enhance signal transmission.
5. Step 5: Based on the definitions and hierarchy, identify that the connective tissue layer directly surrounding individual axons is the endoneurium.