Biceps Femoris Muscle

Biceps Femoris Muscle

Long Head of the Biceps Femoris

Origin: Posterior side of the ischial tuberosity, conjoined with semitendinosus
Insertion: The styloid process of the fibula and the lateral condyle of the tibia
Actions: Flexion of the leg at the knee, external rotation of the knee, extension of the thigh at the hip
Innervation: Tibial portion of the sciatic nerve (L5,S1)
Blood Supply: Branches from the internal iliac, popliteal and profunda femoris arteries

Primary Actions of the Biceps Femoris Long Head

1. Flexion of the leg at the knee

Agonists:

  • Semimembranosus
  • Semitendinosus

Antagonists:

  • Vastus lateralis
  • Vastus medialis
  • Vastus intermedius
  • Rectus Femoris

Gracilissartoriuspopliteusgastrocnemius, and plantaris assist with flexion of the knee

2. External rotation of the knee

Agonists:

  • Biceps femoris (short head)

Antagonists:

  • Popliteus
  • Semitendinosus
  • Semimembranosus

3. Extension of the thigh at the hip

Agonists:

  • Gluteus maximus
  • Semitendinosus
  • Semimembranosus
  • Adductor magnus (posterior fibers)

Antagonists:

  • Psoas Major
  • Iliacus

Short Head Of the Biceps Femoris

Origin:Middle third of the linea aspera
Insertion: The styloid process of the fibula and the lateral condyle of the tibia
Actions: Flexion of the leg at the knee, external rotation of the knee
Innervation: Common peroneal portion of the sciatic nerve (L5, S1)
Blood Supply: Branches from the internal iliac, popliteal and profunda femoris arteries

Primary Actions of the Biceps Femoris Short Head

Primary Actions of the Biceps Femoris Short Head:

1. Flexion of the leg at the knee
Agonists:

  • Semitendinosus
  • Semimembranosus

Antagonists:

  • Vastus lateralis
  • Vastus medialis
  • Vastus intermedius
  • Rectus femoris

Gracilis, sartorius, popliteus, gastrocnemius, and plantaris assist with flexion of the knee

2. External rotation of the knee
Agonists:

  • Biceps Femoris (long head)

Antagonists:

  • Popliteus
  • Semitendinosus
  • Semimembranosus

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