Biceps femoris muscle
Encyclopedia
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 hamstring
s muscle group.
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 fibular (peroneal) nerve
descends along its medial border.
, the linea aspera, the medial supracondylar ridge
of the femur, or from various other parts.
A slip may pass to the gastrocnemius
.
Since the long head originates in the pelvis it is also involved in hip extension. 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.
and is thus innervated by common peroneal branch
of the sciatic nerve
(L5, S1), while the long head is innervated by the tibial branch
of the sciatic nerve (L5, S1).
of a several arteries: the perforating branches
of the profunda femoris artery
, the inferior gluteal artery
, and the popliteal artery
.
Thigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
. As its name implies, it has two parts, one of which (the long head) forms part of the hamstring
Hamstring
In human anatomy, the hamstring refers to any one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the posterior thigh muscles, or the tendons of the semitendinosus, the...
s muscle group.
Origin and insertion
It has two heads of origin;- one, the long head, arises from the lower and inner impression on the back part of the tuberosity of the ischiumTuberosity of the ischium-External links: - "The Female Perineum: Bones" - "Major Joints of the Lower Extremity: Hip bone "...
, by a tendon common to it and the semitendinosusSemitendinosus muscleThe semitendinosus is a muscle in the back of the thigh; it is one of the hamstrings.-Structure:The semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh ....
, and from the lower part of the sacrotuberous ligamentSacrotuberous ligamentThe sacrotuberous ligament is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends....
; - the other, the short head, arises from the lateral lip of the linea asperaLinea asperaThe linea aspera is a ridge of roughened surface on the posterior aspect of the femur, to which are attached muscles and intermuscular septum.Its margins diverge above and below....
, between the adductor magnusAdductor magnus muscleThe adductor magnus is a large triangular muscle, situated on the medial side of the thigh.It consists of two parts. The portion which arises from the ischiopubic ramus is called the "adductor portion", and the portion arising from the tuberosity of the ischium is called the "hamstring portion"...
and vastus lateralisVastus lateralis muscleThe Vastus lateralis is the largest part of the Quadriceps femoris. It arises by a broad aponeurosis, which is attached to the upper part of the intertrochanteric line, to the anterior and inferior borders of the greater trochanter, to the lateral lip of the gluteal tuberosity, and to the upper...
, extending up almost as high as the insertion of the gluteus maximusGluteus maximus muscleThe gluteus maximus is the largest and most superficial of the three gluteal muscles...
; from the lateral prolongation of the linea aspera to within 5 cm. of the lateral condyleLateral condyleLateral condyle can refer to:* Lateral condyle of tibia* Lateral condyle of femur* Lateral condyle on metatarsal...
; and from the lateral intermuscular septumLateral intermuscular septumThe lateral intermuscular septum extends from the lower part of the crest of the greater tubercle of the humerus, along the lateral supracondylar ridge, to the lateral epicondyle; it is blended with the tendon of the Deltoideus, gives attachment to the Triceps brachii behind, to the Brachialis,...
.
The fibers of the long head form a fusiform belly, which passes obliquely downward and lateralward across the sciatic nerve
Sciatic nerve
The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...
to end in an aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
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
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
.
At its insertion the tendon divides into two portions, which embrace the fibular collateral ligament
Fibular collateral ligament
-External links:*...
of the knee-joint
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
.
From the posterior border of the tendon a thin expansion is given off to the fascia
Fascia
A fascia is a layer of fibrous tissue that permeates the human body. A fascia is a connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding those structures together in much the same manner as plastic wrap can be used to hold the contents of sandwiches...
of the leg. The tendon of insertion of this muscle forms the lateral hamstring; the common fibular (peroneal) nerve
Common fibular nerve
The common fibular nerve , about one-half the size of the tibial nerve, is derived from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves.It descends obliquely along the lateral side of the popliteal fossa to the head of the fibula,...
descends along its medial border.
Variations
The short head may be absent; additional heads may arise from the ischial tuberosityTuberosity of the ischium
-External links: - "The Female Perineum: Bones" - "Major Joints of the Lower Extremity: Hip bone "...
, the linea aspera, the medial supracondylar ridge
Medial supracondylar ridge
The inferior third of the medial border of the humerus is raised into a slight ridge, the medial supracondylar ridge , which becomes very prominent below; it presents an anterior lip for the origins of the Brachialis and Pronator teres, a posterior lip for the medial head of the Triceps brachii,...
of the femur, or from various other parts.
A slip may pass to the gastrocnemius
Gastrocnemius muscle
In humans, the gastrocnemius muscle is a very powerful superficial pennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle...
.
Action
Both heads of the biceps femoris perform knee flexion.Since the long head originates in the pelvis it is also involved in hip extension. 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.
Innervation
The short head of the biceps femoris develops in the flexor compartment of the thighPosterior compartment of thigh
The posterior fascial compartment of the thigh contains the knee flexors and hip extensors.It consists of the following muscles:* biceps femoris* semitendinosus* semimembranosus...
and is thus innervated by common peroneal branch
Common fibular nerve
The common fibular nerve , about one-half the size of the tibial nerve, is derived from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves.It descends obliquely along the lateral side of the popliteal fossa to the head of the fibula,...
of the sciatic nerve
Sciatic nerve
The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...
(L5, S1), while the long head is innervated by the tibial branch
Tibial nerve
The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus.In the popliteal fossa the nerve gives off branches to gastrocnemius, popliteus, soleus and plantaris muscles, an articular branch to the knee joint, and a...
of the sciatic nerve (L5, S1).
Blood supply
The muscle's vascular supply is derived from the anastomosesAnastomosis
An anastomosis is the reconnection of two streams that previously branched out, such as blood vessels or leaf veins. The term is used in medicine, biology, mycology and geology....
of a several arteries: the perforating branches
Perforating arteries
The perforating arteries, usually three in number, are so named because they perforate the tendon of the Adductor magnus to reach the back of the thigh....
of the profunda femoris artery
Profunda femoris artery
The profunda femoris artery is a branch of the femoral artery that, as its name suggests, travels more deeply than the rest of the femoral artery.-Structure:...
, the inferior gluteal artery
Inferior gluteal artery
The inferior gluteal artery , the larger of the two terminal branches of the anterior trunk of the internal iliac artery, is distributed chiefly to the buttock and back of the thigh....
, and the popliteal artery
Popliteal artery
In human anatomy, the popliteal artery is defined as the extension of the "superficial" femoral artery after passing through the adductor canal and adductor hiatus above the knee...
.