muscles of the posterior thigh and popliteal fossa and knee

Question 0

semitendinosus

Answer 0

Origin: ischial tuberosity
Insertion: medial surface of superior part of tibia
Innervation: tibial division of sciatic nerve (L5, S1, S2)
Action: extend hip joint; flex knee joint and rotate the leg medially when knee is flexed; when hip and knee are flexed, can extend trunk

Question 1

biceps femoris

Answer 1

Origin: long head: ischial tuberosity
short head: linea aspera and lateral supracondylar line of femur
Insertion: lateral side of head of fibula; tendon is split by fibular collateral ligament of knee
Innervation: long head: tibial division of sciatic nerve (L5, S1, S2)
short head: common fibular division of sciatic nerve (L5, S1, S2)
Action: flexes knee joint and rotates it laterally when knee is flexed; extends hip joint (e.g. when starting to walk)

Question 2

semimembranosus

Answer 2

Origin: ischial tuberosity
Insertion: posterior part of medial condyle of tibia; reflected attachment forms oblique popliteal ligament (to lateral femoral condyle)
Innervation: tibial division of sciatic nerve (L5, S1, S2)
Action: tibial division of sciatic nerve (L5, S1, S2)
Action: extend hip joint; flex knee joint and rotate the leg medially when knee is flexed; when hip and knee are flexed, can extend trunk

Question 3

gastrocnemius

Answer 3

Origin: lateral head: lateral aspect of lateral condyle of femur
medial head: popliteal surface of femur, superior to medial condyle
Insertion: posterior surface of calcaneus via calcaneal tendon
Innervation: tibial nerve (S1, S2)
Action: plantarflexes ankle when knee is extended; raises heel during walking; and flexes knee joint