Which muscle is innervated by the obturator nerve?

• A. Gracilis
• B. Semitendinosis
• C. Gastrocnemius
• D. Biceps femoris

Answer: (A)

The correct answer is the gracilis muscle, which is innervated by the obturator nerve. The obturator nerve is primarily responsible for innervating the muscles located in the medial compartment of the thigh, which includes the gracilis. This muscle plays a crucial role in adducting the thigh and assisting with knee flexion.

The other muscles listed are innervated by different nerves and have distinct functions. The semitendinosus, part of the hamstring group, is mainly innervated by the sciatic nerve, specifically its tibial division. The gastrocnemius, a major calf muscle involved in plantarflexion of the foot and flexion of the knee, is innervated by the tibial nerve, which is a branch of the sciatic nerve. Lastly, the biceps femoris, also a hamstring muscle, receives its nerve supply from the sciatic nerve as well, specifically its fibular division for the short head and the tibial division for the long head.

Understanding the specific innervation of these muscles highlights the importance of the obturator nerve in lower limb function, particularly in movements involving adduction and stabilization of the leg.