| Biceps femoris | |
|---|---|
| Lateral aspect of right leg. Biceps femoris muscle long head labeled | |
| Same picture with the visible part of the short head beneath the long head labeled | |
| Latin | musculus biceps femoris |
| Gray's | subject #128 478 |
| Origin | tuberosity of the ischium, linea aspera, femur |
| Insertion | the head of the fibula which articulates with the back of the lateral tibial condyle |
| Artery | inferior gluteal artery, perforating arteries, popliteal artery |
| Nerve | long head: tibial nerve short head: common peroneal nerve |
| Actions | flexes knee joint, laterally rotates knee joint (when knee is flexed), extends hip joint (long head only) |
| Antagonist | Quadriceps muscle |
The biceps femoris is a muscle of the posterior (the back) thigh. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group.
Contents |
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.[1]
At its insertion the tendon divides into two portions, which embrace the fibular collateral ligament of the knee-joint.[1]
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 fibular (peroneal) nerve descends along its medial border.[1]
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.[1]
A slip may pass to the gastrocnemius.[1]
Both heads of the biceps femoris perform knee flexion.[2]
Since the long head originates in the pelvis it is also involved in hip extension.[2] The long head of the biceps 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 of the biceps femoris develops in the flexor compartment of the thigh and is thus innervated by common peroneal branch of the sciatic nerve (L5, S2), while the long head is innervated by the tibial branch of the sciatic nerve (L5, S2).[3]
The muscle's vascular supply is derived from the anastomoses of a several arteries: the perforating branches of the profunda femoris artery, the inferior gluteal artery, and the popliteal artery.[3]
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.
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