Synovial Joints (9-2)
Five accessory structures of synovial joints
1) Cartilages 2) Fat pads 3) Ligaments 4) Tendons 5) Bursae
Four factors that stabilize synovial joints
1) Collagen fibers (joint capsule, ligaments) 2) Shape of the articulating surfaces and menisci 3) Presence of other bones, muscles, or fat pads 4) Tension in the tendons of articulating bones - these prevent injury by limiting range of motion - pain receptors are not found on the inside of synovial joints - pain felt due to joint damage results from nerves that monitor the capsule, ligaments, and tendons
Two synovial joint injuries
1) Dislocation (luxation) 2) Subluxation
Three synovial fluid functions
1) Lubrication 2) Nutrient distribution 3) Shock absorption
Subluxation
A partial dislocation - double jointed people have weakly stabilized joints that are prone to dislocation or partial dislocation - second of two synovial joint injuries
Bunion
Abnormal enlargement of the joint at the base of the big toe - affects the accessory organ "bursae"
Fat pads
Adipose tissue superficial to the joint capsule - protect articular cartilages - second of five accessory structures of synovial joints
Articular capsules
An envelope surrounding a synovial joint - prevents bones from touching
Articular disc
Another name for meniscus
Diarthroses
Another name for synovial joints
Articulating surfaces
Any surface of a bone that makes normal direct contact with another bone as part of a synovial joint - bone ends at movable joints - cushioned by articular cartilage pad
Lubrication
Articular cartilage act as sponge filled with fluid - compression of it pushes some fluid out - first of three synovial joint functions
Dislocation (luxation)
Articulating surfaces forced out of position - damages articular cartilage, ligaments, joint capsule - shoulder joint most prone to this injury - caused by extreme stress on joint - first of two synovial joint injuries
Tendons
Attach bone to muscles around joint - helps support joint - fourth of five accessory structures of synovial joints
Chondrocytes
Cells that secrete cartilage
Ligaments
Connects bone to bone - supports and strengthens joints - continuous with periosteum of articulating bones - no direct blood supply - sprains can occur here - third of five accessory structures of synovial joints
Synovial fluid composition
Contains slippery proteoglycans secreted by fibroblasts - has consistency of heavy molasses - resembles interstitial fluid, not much in joint - example: knee joint only has up to 3 mL of fluid
Articular cartilages
Cover the bone ends at movable joints - prevents bones from touching - lubricated by synovial fluid - pads articular surfaces within articular capsules
Cartilages
Cushion the joint - fibrocartilage pad called a meniscus located between opposing bones in synovial joint to cushion the joint - first of five accessory structures of synovial joints
Meniscus
Fibrocartilage pad located between opposing bones in synovial joint to cushion - makes up the accessory organ "cartilage" - also called articular disc - singular
Nutrient distribution
Fluid circulates as joint moves - provides nutrients to chondrocytes in area - second of three synovial joint functions
Synovial joints
Freely movable joints - third of three functional classifications for joint function (or joint movement)
Bursitis
Inflamed bursae causing pain - can result from repetitive motion, irritation, trauma, infection - i.e., bunion
Sprain
Ligaments with torn collagen fibers
Synovial fluid (general)
Lubricates smooth surfaces of articular cartilages - has consistency of heavy molasses - functions to reduce friction
Synovial membrane
Membrane that lines the capsule of a synovial joint
Menisci
Plural of meniscus
Bursae
Pockets of synovial fluid that cushion areas where tendons or ligaments rub - lined by synovial membrane - fifth of five accessory structures of synovial joints
Proteoglycans
Proteins with long chains of sugars - found within synovial fluid - secreted by fibroblasts
Bursa
Singular of bursae
Shock absorption
Viscosity (thicknes) of fluid increases with increased pressure to absorb shock - third of three synovial joint functions