Joints Synovial fluid and cartilage Flashcards
Types of fibrous joints with an example of each?
> Suture - Bones of the cranium
Periodontal - Holds tooth in socket
Interosseus - Joint held together by ligament, e.g. the fibula and tibia
Suture joint?
A fibrous joint held together with short, interconnecting fibres, and bone edges interlock, found only in the skull
Interosseus joint?
A fibrous joint held together by a ligament. Fibrous tissue can vary in length but is longer than sutures
Periodontal joint?
Peg-in-socket fibrous joint. Periodontal ligament holds tooth in socket
Primary cartilaginous joint?
- Synchondrosis
- Only hyaline cartilage
- Examples = Epiphyseal plate, sternomanubrial joint and first rib and sternum
Secondary cartilaginous joint
- Symphysis
- Hyaline and fibrocartilage
- Examples = Intervertebral joints and pubic symphysis
What are the common features of a synovial joint?
1) Fibrous capsule
2) Synovial membrane
3) Articular cartilage
4) Synovial cavity (fluid-filled)
May also contain:
- Articular discs
- Ligaments
- Bursae
Examples of synovial joint types?
> Plane - Vertebrae > Hinge - Elbow > Pivot - Radio-ulnar > Condylar - Radiocarpal > Saddle - thumb > Ball and socket - Shoulder
What determines joint stability?
> Shape of articulating surfaces
Capsule and ligaments
Muscles
Which cartilage is present in a synovial joint?
Hyaline and fibrocartilage
What is the “make up” of hyaline (Articular) cartilage?
1) Superficial/tangential layer:
- Flattened chondrocytes that produce collage and glycoproteins (e.g. lubrincin)
- Horizontal orientation
2) Transitional layer:
- Round chondrocytes that produce proteoglycans such as aggrecan
- Collagen is orientated on a slant
3) Deep:
- Collagen is vertical orientation
What does the superficial layer of articular (Hyaline) cartilage produce?
Collagen and glycoproteins e.g. lubricin
What does the transitional layer of articular (Hyaline) cartilage produce?
Proteoglycans such as aggrecan
What are glycoproteins?
> Example - Lubricin
Proteins to which oligosaccharide chains are attached
More protein than carbohydrate
What are proteoglycans?
> Example - Aggrecan
Protein that are heavily glycosylated. A protein core to which one or more GAGs attach
Tend to be more carb than protein
What are glycosaminoglycans?
> Example - Hyaluronic acid
> Long unbranched polysaccharides, which are highly polar and thus attract water
Are glycosaminoglycans hydrophobic or -phillic and why?
Hydrophillic as they are highly polar
How thick is the average cartilage?
2-3mm
How thick is interphalangeal cartilage?
1 mm
How thick is patella cartilage?
5-6 mm
What does cartilage lack?
- Avascular
- Aneural
- Alymphatic
What produced synovial fluid and where?
Produced by synoviocytes in the synovium
What is the Synvoium composed of?
> Synoviocytes which produce synovial fluid
Rich capillary network
No epithelial lining
What is the role of the synovium?
Direct exchange of oxygen, carbon dioxide and metabolites between blood and synovial fluid
Type A synoviocytes?
> Look like macrophages
Remove debris
Contribute to synovial fluid production
Type B synoviocytes?
> Fibroblast like
> Main producer of synovial fluid
Density of synovial fluid?
Viscous fluid
What is synovial fluid composed of?
> Hyaluronic acid and lubricin
> Fluid component, from the blood plasma
Volume of synovial fluid?
Small volumes e.g. knee joint = 0.5ml
Turnover of synovial fluid?
Rapid turnover = 2 hours
What is the role of synovial fluid?
1) Nutrition of cartilage
2) Removal of waste products
3) Lubrication –> less friction
- -> Less wear
How does synovial fluid lubricate?
1) Boundary:
- Glycoproteins such as lubricin bind t receptors on the articular surface to forma. thin film
2) Hydrodynamic:
- Surfaces are kept apart by the liquid pressure
- Viscosity changes with load and velocity of movement
3) Weeping:
- Fluid is present in the cartilage is squeezed out into the synovial cavity to increase fluid volume
What is the coefficient of friction in a synovial joint?
0.002-0.2
What is the role of a bursae?
A fluid filled pad that acts to reduce friction within the synovial membrane
What happens to the viscosity of synovial fluid as you age, what is the result of this?
Viscosity increase:
- Slower joint movements
- Reduced lubrication
What happens to the water content of cartilage within synovial joints as you age, what is the result of this?
Water content of cartilage is decreased = Reduced shock absorption
What occurs within synovial joints as we age, what is the result of this?
1) Viscosity of synovial fluid increases
2) Water content of cartilage is decreased
Results in less protection of articular surfaces and increased risk of damage
What occur as a result of osteoarthritis?
- Bone spurs
- Narrowing of intervertebral discs
