Which nerve is the longest and thickest in the body?

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

Answer: (B)

The longest and thickest nerve in the body is the sciatic nerve. Its length comes from its course from the lower spinal cord all the way down the leg: it originates from the lumbosacral plexus (L4–S3), travels through the gluteal region and down the posterior thigh, and then splits into the tibial and common fibular nerves near the knee. Its diameter is large because it carries a vast amount of motor and sensory information to and from the entire lower limb.

It helps to contrast with the other nerves mentioned: the vagus nerve is the longest nerve overall when you count cranial nerves, but it runs from the brainstem through the neck into the chest and abdomen rather than along the whole body like a peripheral nerve; the median and radial nerves are long, but they run in the upper limb and are not as long or as thick as the sciatic nerve.