Joints (articulations): connections where two bones meet; site of body movement.
Movement involves a trade-off between mobility and strength.
Classified using two schemes: Structural (anatomy) and Functional (range of motion).
Fibrous: bones connected by fibrous tissue.
Cartilaginous: bones connected by cartilage.
Bony (Ossification): two bones fuse together.
Synovial: freely movable joints.
Synarthrosis: immovable joint.
Amphiarthrosis: slightly movable joint.
Diarthrosis: freely movable joint.
Very strong with no movement; critical for function.
Types include:
Suture: found in skull; edges interlock.
Gomphosis: connects teeth to bony sockets via periodontal ligament.
Synchondrosis: bones bridged by hyaline cartilage (e.g., ribs and sternum).
Synostosis: formed when bones fuse (e.g., mandibular bones in infants).
More movable than synarthrosis; stronger than diarthrosis.
Types include:
Syndesmosis: bones connected by ligaments (e.g., distal tibia-fibula).
Symphysis: bones connected by fibrocartilage (e.g., pubic symphysis).
Freely movable; located at the ends of long bones.
Surrounded by joint capsule containing:
Inner synovial membrane.
Outer fibrous capsule.
Synovial fluid that fills the joint cavity.
Articular cartilage covering articulating surfaces.
About 3 mL, similar to egg yolk.
Functions:
Lubrication: reduces friction.
Nutrient distribution: absorbs/diffuses nutrients and waste.
Shock absorption: viscosity increases with pressure.
Components:
Quadriceps tendon, patella, joint capsule, synovial membrane, articular cartilage.
Accessory structures include ligaments, fat pads, bursa, and meniscus, contributing to joint stability.
Cartilages: Meniscus (fibrocartilage pad).
Fat pads: to protect articular cartilages and fill space during movement.
Ligaments: connect bone to bone; support joints leading to potential sprains when overstretched.
Tendons: attach muscle to bone (not part of the joint).
Bursae: small pockets of synovial fluid for cushioning.
Prevents damage from excessive movements through:
Collagen fibers of the joint capsule and ligaments.
Shape of articulating surfaces and menisci.
Other support structures (bones, muscles, fat pads, tendons).