Which nerve is described as the longest and thickest in the body?

• A. Median nerve
• B. Ulnar nerve
• C. Radial nerve
• D. Sciatic nerve

Answer: (D)

Think about a nerve that has to span a large portion of the lower limb to supply many muscles and much skin from the hip down to the foot. That nerve is the sciatic nerve. It travels from the lumbosacral plexus (L4–S3), courses through the gluteal region, down the posterior thigh, and then splits near the knee into the tibial and common fibular nerves to reach the leg and foot. Because it carries a vast amount of motor and sensory fibers over a long distance, it has a large diameter, making it the thickest nerve in the body. The other nerves listed stay in the upper limb or cover shorter regions, so they don’t reach the same combination of length and cross‑sectional size as the sciatic nerve.