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Biceps femoris muscle
Origin and insertion
It has two heads of origin;
The fibers of the long head form a fusiform belly, which passes obliquely downward and lateralward across the sciatic nerve to end in an aponeurosis which covers the posterior surface of the muscle, and receives the fibers of the short head; this aponeurosis becomes gradually contracted into a tendon, which is inserted into the lateral side of the head of the fibula, and by a small slip into the lateral condyle of the tibia.
At its insertion the tendon divides into two portions, which embrace the fibular collateral ligament of the knee-joint.
From the posterior border of the tendon a thin expansion is given off to the fascia of the leg. The tendon of insertion of this muscle forms the lateral hamstring; the common peroneal nerve descends along its medial border.
Both heads of the Bicep Femoris perform knee flexion. Since the long head originates in the pelvis it is also involved in hip extension. The long head of the bicep femoris is a weaker knee flexor when the hip is extended (because of active insufficiency). For the same reason the long head is a weaker hip extender when the knee is flexed.
When the knee is semi flexed, the Biceps femoris in consequence of its oblique direction rotates the leg slightly outward
The short head may be absent; additional heads may arise from the ischial tuberosity, the linea aspera, the medial supracondylar ridge of the femur, or from various other parts.
A slip may pass to the gastrocnemius.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Biceps_femoris_muscle". A list of authors is available in Wikipedia.|