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