what is the largest nerve
1 It innervates muscles in the arm that extend the elbow and muscles in the forearm, which enables the wrist and fingers to straighten or extend.  Sciatic nerve â The sciatic nerve is the largest single nerve in the body, extending from the back of the pelvis down the back of the thigh. It is the primary nerve of the leg and is responsible for innervating the muscles in the hip and lower limbs (including the tibial nerve and common fibular nerve).