The sartorius, semitendinous and gracilis all make up the pes anserine tendon. Vastus medialis, although on the medial aspect of the knee, does not make up this muscle group as it inserts to the tibial tubercle via the patellar tendon.

For this question, we are looking for a muscle that is located in the lateral compartment of the thigh. In addition, this muscle should contract when the thigh is either abducted or medially rotated. The correct answer is the tensor fasciae latae which is the only muscle of the choices that fits these categories.

Both the superior gemellus and the obturator internus muscles are innervated by the same nerve. The nerve that innervates the obturator internus is easy to remember because the nerve and the muscle have the same name. That means the obturator internus nerve is the correct answer.

The largest muscle in the entire body is the Gluteus Maximus which is found in the buttocks. It has the function of keeping the entire body erect by inserting itself in the pelvic bone.

Sartorius, gracilis, semitendinosus make up the pes anserine group whose conjoined tendons insert onto the anteromedial surface of the proximal extremity of the tibia. They flex and medially rotate the leg at the knee joint.

The hamstring muscles consist of three posterior muscles and their tendons (semitendinosus, semimembranosus, and biceps femoris). The hamstring muscles are responsible for knee flexion and hip extension. The semitendinosus, semimembranosus, and the long head of biceps femoris all originate at the ischial tuberosity (having these muscles cross the hip joint), while the short head of biceps femoris originate at the linea aspera and the lateral supracondylar line of the femur.

The flexor digitorum brevis lies in the middle of the sole of the foot above the plantar aponeurosis. It arises from a tendon from the medial process of the calcaneus, it continues towards the toes and divides into four tendons, one for each of the four lesser toes. It is innervated by the medial plantar nerve. The tibialis posterior, extensor digitorum longus, and soleus all cross the ankle joint thus having leverage above it.

The psaos major and the iliacus muscles are distinct in the abdomen and unite at the level of the inguinal ligament to form the iliopsoas muscle in the thigh. The iliopsoas muscle crosses the hip joint and inserts on to the lesser trochanter of the femur. The iliopsoas is involved in flexion and lateral rotation of the thigh. It is the strongest of the hip flexors, and is important in standing, walking, and running.

The gluteus medius, gluteus minimus, and piriformis insert onto the greater trochanter.

For this question, we are looking for a muscle that lies in the posterior, superficial compartment of the leg. This eliminates the gracilis muscle, leaving the planters, gastrocnemius, and soles muscles. The correct answer is the plantaris muscle which is a small muscle in the posterior compartment of the leg that has a long tendon and little to no function. Both the gastrocnemius and soleus muscles are larger and more important in walking and running.

The tendons of the sartorius, gracilis, and semitendinosus muscles combine and expand to form the pes anserinus. These muscles combine at the medial boarder of the tibial tuberosity.

Fun fact: the pes anserinus may be used in the surgical repair of the knee joint’s anterior cruciate ligament.

The rectus femoris is an anterior muscle of the thigh, and is a member of the quadriceps. It inserts at the base of the patella at the tibial tuberosity. Like all the quadriceps it helps extend the leg and is innervated by the femoral nerve.