Biceps femoris muscle
| Biceps femoris muscle |
|---|
|
| back thigh muscles (M. biceps femoris emerge.) of humans |
| origin |
|
Caput longum : ischial tuberosity ( tuber ischiadicum ) Caput breve : back of the thigh bone |
| approach |
| Fibula ( caput fibulae ) below the knee joint |
| function |
| Flexion and external rotation of the knee joint, extension and external rotation of the hip joint |
| Innervation |
|
Caput longum : Nervus tibialis Caput breve : Nervus peronaeus communis |
| Spinal segments |
| L5, S1 |
The muscle biceps femoris ( Latin for "two-headed muscle of the thigh ", in German called "thigh flexor" or "leg curl") is a skeletal muscle with two muscle heads .
In the even-toed ungulates of the muscle is the gluteus superficial to muscle gluteobiceps grown. In quadruped mammals, an ancillary tendon of the biceps femoris muscle (heel tendon, Tendo accessorius ) radiates into the Achilles tendon .
function
The long head acts on both the hip joint and the knee joint as well as the other two muscles of the sciocrural muscles , the Mm. semitendinosus and semimembranosus. It causes extension and external rotation in the hip joint and flexion in the knee joint. The short head only affects the knee joint. Thus, both muscles flex the knee joint and can turn the lower leg outward when the knee joint is bent .
In quadruped mammals, the action of the biceps femoris muscle is even more complex. In addition to stretching and abduction of the hip joint, when the leg is placed on it ("support leg") it helps to stretch the knee (because the lower leg is fixed to the floor), and when the leg is raised ("hanging leg") it acts as a knee flexor. Thanks to its heel tendon, the muscle also acts as an extensor for the ankle .
The involvement of the biceps femoris muscle (and the other two muscles of the ischiocrural muscles , the semitendinosus and semimembranosus muscles ) in stretching the knee joint is known in humans as the Lombard paradox .
Varieties
Sometimes the caput breve is missing. The external rotation in the flexed knee joint must then be carried out by the long head alone.
Individual evidence
- ^ A b Franz-Viktor Salomon: muscle tissue. In: Anatomy for veterinary medicine. 2nd ext. Edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , pp. 147-234.
- ^ JG Andrews: The functional roles of the hamstrings and quadriceps during cycling: Lombard's Paradox revisited . In: J Biomech . tape 20 , no. 6 , 1987, pp. 565-75 , doi : 10.1016 / 0021-9290 (87) 90278-8 , PMID 3611133 .