13.2
Classification fonctionnelle des articulations
Functional Classification of Joints
La classification fonctionnelle des articulations est déterminée par le degré de mobilité entre les os adjacents.…
Les articulations peuvent être classées fonctionnellement en trois catégories en fonction de leur mobilité.
Les synarthroses sont des articulations immobiles, les amphiarthroses sont des articulations légèrement mobiles et les diarthroses sont des articulations librement mobiles.
Les synarthroses et les amphiarthroses sont des articulations stables constituées de tissus conjonctifs fibreux ou cartilagineux.
Des exemples de synarthroses sont les articulations fibreuses entre les dents et les alvéoles dentaires, et l’articulation cartilagineuse entre la première paire de côtes et le manubrium du sternum.
Des exemples d’amphiarthroses sont l’articulation fibreuse entre le tibia et le péroné de la jambe, et l’articulation cartilagineuse entre les os pubiens.
Les diarthroses sont des articulations synoviales avec une cavité synoviale remplie de liquide entre les surfaces osseuses articulées. En raison de leur stabilité plus faible par rapport aux synathroses et aux amphiarthroses, les diarthroses sont plus sensibles à la luxation.
Des exemples de diarthroses sont les articulations du genou, du coude et de l’épaule.
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Q1: What are the three functional classifications of joints?
Joints are functionally classified based on mobility into three categories: synarthroses are immovable joints providing strong unions between bones; amphiarthroses are slightly movable joints allowing limited motion; and diarthroses are freely movable joints with the greatest range of motion. Each classification reflects the joint's structural composition and functional role in the body.
Q2: How do synarthroses protect internal organs?
Synarthroses are immobile joints that create strong, stable unions between bones, making them ideal for protecting vital organs. Examples include skull sutures that surround and protect the brain, and the manubriosternal joint that unites the sternum to protect the heart. Their immobile nature ensures bones remain firmly positioned around these sensitive structures.
Q3: What role do intervertebral discs play in amphiarthroses?
Intervertebral discs are thick pads of fibrocartilage that fill gaps between vertebrae in amphiarthrotic joints. They strongly unite adjacent vertebrae while allowing limited movement between them. Small individual movements sum along the vertebral column to enable large ranges of body motion despite each joint's restricted mobility.
Q4: Why are diarthroses more susceptible to dislocation than other joint types?
Diarthroses are freely movable synovial joints with a fluid-filled cavity between articulating bone surfaces, providing greater mobility but lower stability compared to synarthroses and amphiarthroses. Their increased range of motion comes at the cost of reduced structural stability, making them more vulnerable to dislocation during extreme movements or trauma.
Q5: How are diarthroses classified based on axes of motion?
Diarthroses are classified into three categories by their axes of motion: uniaxial joints move in one plane, such as the elbow; biaxial joints move in two planes, like metacarpophalangeal joints; and multiaxial joints move in all three anatomical planes, such as the shoulder. This classification determines the range and type of movements each joint can perform.
Q6: What structural tissues compose synarthroses and amphiarthroses?
Both synarthroses and amphiarthroses are stable joints composed of fibrous or cartilaginous connective tissues. Synarthroses include fibrous joints like those between teeth and sockets, while amphiarthroses include cartilaginous joints like the pubic symphysis. These tissue types provide the strength and limited flexibility characteristic of each joint classification.
Q7: Where are most diarthrotic joints located in the skeleton?
Most diarthrotic joints are found in the appendicular skeleton, which includes the limbs and girdles. These synovial joints provide the majority of body movements and give the limbs a wide range of motion. The appendicular skeleton's abundance of diarthroses enables the complex, coordinated movements necessary for locomotion and manipulation of objects.