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femur

femur

definition : femur

The femur (, pl. femurs or femora ) or thigh bone, is the most proximal (closest to the hip joint) bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in the hindlimbs. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with the tibia and kneecap forming the knee joint. By most measures the femur is the strongest bone in the body. The femur is also the longest bone in the human body.

==Structure== The femur is the only bone in the upper leg. The two femurs converge medially toward the knees, where they articulate with the proximal ends of the tibiae. The angle of convergence of the femora is a major factor in determining the femoral-tibial angle. Human females have wider pelvic bones, causing their femora to converge more than in males. In the condition genu valgum (knock knee) the femurs converge so much that the knees touch one another. The opposite extreme is genu varum (bow-leggedness). In the general population of people without either genu valgum or genu varum, the femoral-tibial angle is about 175 degrees.

The femur is the longest and, by most measures, the strongest bone in the human body. Its length on average is 26.74% of a person's height, a ratio found in both men and women and most ethnic groups with only restricted variation, and is useful in anthropology because it offers a basis for a reasonable estimate of a subject's height from an incomplete skeleton.

The femur is categorised as a long bone and comprises a diaphysis (shaft or body) and two epiphyses (extremities) that articulate with adjacent bones in the hip and knee.

===Body===

The body of the femur (or shaft) is long, slender and almost cylindrical in form. It is a little broader above than in the center, broadest and somewhat flattened from before backward below. It is slightly arched, so as to be convex in front, and concave behind, where it is strengthened by a prominent longitudinal ridge, the linea aspera which diverges proximal and distal as the medial and lateral ridge. Proximal the lateral ridge of the linea aspera becomes the gluteal tuberosity while the medial ridge continues as the pectineal line. Besides the linea aspera the shaft has two other bordes; a lateral and medial border. These three bordes separates the shaft into three surfaces: One anterior, one medial and one lateral. Due to the vast musculature of the thigh the shaft can not be palpated. A structure of minor importance in humans, the incidence of the third trochanter varies from 17–72% between ethnic groups and it is frequently reported as more common in females than in males.

===Lower part===

The lower extremity of the femur (or distal extremity) is larger than the upper extremity. It is somewhat cuboid in form, but its transverse diameter is greater than its antero-posterior (front to back). It consists of two oblong eminences known as the condyles.

By the sixth week of development, the first hyaline cartilage model of the femur is formed by chondrocytes. Endochondral ossification begins by the end of the embryonic period and primary ossification centers are present in all long bones of the limbs, including the femur, by the 12th week of development. The hindlimb development lags behind forelimb development by 1–2 days.

==Function== As the femur is the only bone in the thigh, it serves as an attachment point for all the muscles that exert their force over the hip and knee joints. Some biarticular muscles – which cross two joints, like the gastrocnemius and plantaris muscles – also originate from the femur. In all, 23 individual muscles either originate from or insert onto the femur.

In cross-section, the thigh is divided up into three separate fascial compartments divided by fascia, each containing muscles. These compartments use the femur as an axis, and are separated by tough connective tissue membranes (or septa). Each of these compartments has its own blood and nerve supply, and contains a different group of muscles. These compartments are named the anterior, medial and posterior fascial compartments.

===Muscle attachments=== {| class="sortable wikitable" | Muscle || Direction || Attachment |- | Iliacus muscle || Insertion || Lesser trochanter |- | Psoas major muscle || Insertion || Lesser trochanter |- | Gluteus maximus muscle || Insertion || Gluteal tuberosity |- | Gluteus medius muscle || Insertion || Lateral surface of greater trochanter |- | Gluteus minimus muscle || Insertion || Forefront of greater trochanter |- | Piriformis muscle || Insertion || Superior boundary of greater trochanter |- | Gemellus superior muscle || Insertion || Upper edge of Obturator internus's tendon (indirectly greater trochanter) |- | Obturator internus muscle || Insertion || Medial surface of greater trochanter |- | Gemellus inferior muscle || Insertion || Lower edge of Obturator internus's tendon (indirectly greater trochanter) |- | Quadratus femoris muscle || Insertion || Intertrochanteric crest |- | Obturator externus muscle || Insertion || Trochanteric fossa |- | Pectineus muscle || Insertion || Pectineal line |- | Adductor longus muscle || Insertion || Medial ridge of linea aspera |- | Adductor brevis muscle || Insertion || Medial ridge of linea aspera |- | Adductor magnus muscle || Insertion || Medial ridge of linea aspera and the adductor tubercle |- | Vastus lateralis muscle || Origin || Greater trochanter and lateral ridge of linea aspera |- | Vastus intermedius muscle || Origin || Front and lateral surface of femur |- | Vastus medialis muscle || Origin || Distal part of intertrochanteric line and medial ridge of linea aspera |- | Short head of biceps femoris || Origin || Lateral ridge of linea aspera |- | Popliteus muscle || Origin || Under the lateral epicondyle |- | Articularis genu muscle || Origin || Lower 1/4 of anterior femur deep to vastus intermedius |- | Gastrocnemius muscle || Origin || Behind the adductor tubercle, over the lateral epicondyle and the popliteal facies |- | Plantaris muscle || Origin || Over the lateral condyle |}

==Clinical significance==

===Fractures===

A femoral fracture that involves the femoral head, femoral neck or the shaft of the femur immediately below the lesser trochanter may be classified as a hip fracture, especially when associated with osteoporosis. Femur fractures can be managed in a pre-hospital setting with the use of a traction splint.

==Other animals==

In primitive tetrapods, the main points of muscle attachment along the femur are the internal trochanter and third trochanter, and a ridge along the ventral surface of the femoral shaft referred to as the adductor crest. The neck of the femur is generally minimal or absent in the most primitive forms, reflecting a simple attachment to the acetabulum. The greater trochanter was present in the extinct archosaurs, as well as in modern birds and mammals, being associated with the loss of the primitive sprawling gait. The lesser trochanter is a unique development of mammals, which lack both the internal and fourth trochanters. The adductor crest is also often absent in mammals or alternatively reduced to a series of creases along the surface of the bone.

Some species of whales, snakes, and other non-walking vertebrates have vestigial femurs.

One of the earliest known vertebrates to have a femur is the eusthenopteron, a prehistoric lobe-finned fish from the Late Devonian period.

Structures analogous to the third trochanter are present in mammals, including some primates.

===Invertebrates=== In invertebrate zoology the name femur appears in arthropodology. The usage is not homologous with that of vertebrate anatomy; the term "femur" simply has been adopted by analogy and refers, where applicable, to the most proximal of (usually) the two longest jointed segments of the legs of the arthropoda. The two basal segments preceding the femur are the coxa and trochanter. This convention is not followed in carcinology but it applies in arachnology and entomology. In myriapodology another segment, the prefemur, connects the trochanter and femur.

==Additional images== Image:Femur - animation9.gif|Position of femur (shown in red). Pelvis and patella are shown as semi-transparent. Image:Fumur Posterior annoted.png|View from behind. Image:Fumur Anterior annoted.png|View from the front. File:Long Bone (Femur).png|Long Bone (Femur) Image:Slide2DADE.JPG|Muscles of thigh. Lateral view. Image:Slide2EA.JPG|Muscles of thigh. Cross section. File:Blausen 0401 Femur DistributionofForces.png|Distribution forces of the femur

==References==

==External links== * * *

Category:Bones of the lower limb Category:Long bones

Texte soumis à la licence CC-BY-SA. Source : Article https://en.wikipedia.org/wiki/Femur de Wikipédia

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