Question 7

Vastus lateralis is the muscle located on the side surface of the lower extremity.

The vastus lateralis is one of the four muscles that comprise the quadriceps group and is specifically positioned on the lateral side of the thigh, making it the correct answer to the question.

A) Vastus lateralis

Vastus lateralis is indeed located on the side surface of the lower extremity. It plays a crucial role in extending the knee and is situated laterally in relation to the other quadriceps muscles, confirming its positioning as described in the question.

B) Gastrocnemius

The gastrocnemius is a major calf muscle located at the back of the lower leg, making it incorrect in the context of the quadriceps group. It does not contribute to the extension of the knee in the same way as the quadriceps muscles, including the vastus lateralis.

C) Anterior tibialis

The anterior tibialis is located on the front of the lower leg, specifically in the anterior compartment, and is not part of the quadriceps group. Its primary function involves dorsiflexion of the foot rather than knee extension, rendering this option incorrect.

D) Rectus femoris

While the rectus femoris is part of the quadriceps group, it is located more centrally and anteriorly in the thigh rather than on the side surface. Thus, it does not fit the description provided in the question, making it an incorrect choice.

Conclusion

The vastus lateralis is the only muscle among the options that is correctly identified as being situated on the side surface of the lower extremity. Other options either belong to different muscle groups or do not occupy the specified location, thus confirming the vastus lateralis as the definitive correct answer.