Joints, Synovial Fluid and Cartilage Flashcards
What are the different types of joint?
Fibrous - bone to bone with fibrous connective tissue and collagen fibres between
Cartilaginous - bone to bone with cartilage between
Synovial
Give an example of a fibrous joint
Periodontal ligament
Cranial sutures
Interosseous membrane
Give an example of a cartilaginous joint
Primary cartilage - synchondrosis
Secondary cartilaginous - symphysis
What is the difference between primary and secondary cartilaginous joints?
Primary cartilaginous contain only hyaline cartilage, secondary cartilaginous contain hyaline and fibrocartilage
What are the common features of synovial joints?
Synovial cavity, fluid filled
Articular cartilage
Fibrous capsule
Synovial membrane
May also contain articular discs, ligaments and bursae
What is joint stability dependent on?
Shape of articulating surfaces
Capsule and ligaments
Muscles
What are the types of synovial joints?
Plane Hinge Pivot Condylar Saddle Ball and socket
What is the structure of articular cartilage?
Superficial/tangential layer - flattened chondrocytes that produce collagen and glycoproteins
Transitional layer - round chondrocytes that produce proteoglycans
Change in collagen orientation from superficial to deep layers
What percentage of articular cartilage is made up of water?
> 75%
What are glycoproteins?
Proteins to which oligosaccharide chains are attached, more protein than carbohydrate e.g. lubricin
What are proteoglycans?
Proteins that are heavily glycosylated i.e. a protein core to which one or more GAGs attach, tend to be more carbohydrate than protein e.g. aggrecan
What are glycosaminoglycans?
Long unbranched polysaccharides which are highly polar and attract water e.g. hyaluronic acid
How are nutrients transported to cartilage and waste products removed?
Via synovial fluid produced by the synovial membrane, as cartilage is avascular, aneural and alymphatic
What are the features of synovium?
Synoviocytes produce the fluid
Rich capillary network
No epithelial lining
Direct exchange of oxygen, carbon dioxide and metabolites between blood and synovial fluid
What are the functions of type a synoviocytes?
Look like macrophages
Remove debris
Contribute to synovial fluid production
What are the functions of type b synoviocytes?
Fibroblast like
Main producer of synovial fluid
What are the features of synovial fluid?
Viscous fluid Contains hyaluronic acid and lubricin Fluid component from blood plasma Present in small volumes e.g. 0.5ml in knee joint Rapid turnover - around 2 hours
What are the functions of synovial fluid?
Nutrition of cartilage and menisci/discs
Removal of waste products
Lubrication (results in less friction and less water)
What is boundary lubrication?
Glycoproteins such as lubricin bind to receptors on the articular surfaces to form a thin film
What is hydrodynamic lubrication?
Like aquaplaning - surfaces are kept apart by liquid pressure, viscosity changes with load and velocity of movement
What is weeping lubrication?
Where fluid that is present in the cartilage is squeezed out into the synovial cavity to increase fluid volume
What are the features and functions of the bursae?
Fluid filled
Synovial membrane
Reduce friction
Cause bursitis when inflammation/irritation occurs
What is the effect of ageing on the viscosity of synovial fluid?
Viscosity of synovial fluid increases with age, resulting in slower joint movements and reduced lubrication
What is the effect of ageing on the water content of cartilage?
Water content of cartilage decreases with ageing, resulting in reduced shock absorption
What do the effects of ageing on the viscosity of synovial fluid and water content of cartilage result in?
Less protection of articular surfaces and increased risk of damage
