Semimembranosus Muscle
Origin: Posterior surface of the ischial tuberosity, deep to the conjoined tendon of the semitendinosus and the long head of the biceps femoris.
Insertion: Posterior aspect of the medial condyle of tibia, sending fibers into the fascia over popliteal ligament.
Actions: Extension of the thigh at the hip, flexion of the leg at the knee, internal rotation of the knee when the knee is flexed
Innervation: Tibial portion of the sciatic nerve (L5, S1, S2)
Blood Supply: Branches from the internal iliac, popliteal, and profunda femoris arteries.
Primary Actions of the Semimembranosus
1. Extension of the thigh at the hip
Agonists:
- Gluteus maximus
- Semitendinosus
- Biceps femoris (long head)
- Adductor magnus (posterior part)
Antagonists:
- Psoas major
- Iliacus
2. Flexion of the leg at the knee
Agonists:
- Biceps femoris
- Semitendinosus
Antagonists:
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
- Rectus femoris
Gracilis, sartorius, popliteus, gastrocnemius, and plantaris assist with flexion of the knee.
3. Internal rotation of the knee when the knee is flexed
Agonists:
- Popliteus
- Semitendinosus
Antagonists:
- Biceps Femoris
Sartorius and gracilis assist with internal rotation of the knee when the knee is flexed.
Advertisement
Muscle Pain Information: The semimembranosus muscle contributes to pain just below the buttock that descends into the back of the thigh and knee.
An excellent book for those beginning the study of anatomy. Coloring helps memory retention.
For intermediary anatomy students learning skeletal and muscle structure.
For beginning and intermediary anatomy . Muscle overlays on the human body. Excellent visuals!