Joints, Synovial fluid and Cartilage Flashcards
3 types of joints
Fibrous
Cartilaginous
Synovial
3 examples of fibrous joints
Periodontal ligament (between tooth and socket) Cranial sutures Interosseous membranes (in limbs, between radius and ulna and tibia and fibia)
Two types of cartilaginous joints
Primary (synchrondosis)
Secondary (Symphysis)
What is primary cartilaginous joints for?
Long bone growth
What do primary cartilaginous joints contain?
Only hyaline cartilage
In primary cartilaginous joints, where does the growth occur?
In the hyaline cartilage
In secondary cartilaginous joints, what do they contain?
Hyaline cartilage AND fibrocartilage
Features of a synovial joint
Strong collagen fibres
Synovial cavity filled with synovial fluid
Synovial joints may or may not contain what?
Articular discs e.g. TMJ
Ligaments
Bursae
Types of synovial joints
Plane Hinge Pivot Condylar (ellipsoid) Saddle Ball and socket
Which type of cartilage is mechanically the weakest?
Hyaline cartilage
What gives a joint its stability?
Shape of articulating surfaces
Capsules and ligaments surrounding joints
Muscles surrounding or crossing joints
What is another name for hyaline cartilage?
Articular cartilage
Layers of hyaline cartilage
Superficial/tangenital layer
Transitional layer
Deep layer
Features of superficial/tangenital layer of hyaline cartilage
Flattened chondocytes (cartilage cells) that produce collagen and glycoproteins Collagen fibres same direction due to shear forces -> a lot stronger and resistant to tear
Features of the transitional layer of hyaline cartilage
Round chondrocytes that produce proteoglycans such as aggrecan (this is good for binding to/attracting water)
What are chondrocytes?
Cartilage cells
What do chondrocytes produce?
Collagen
Glycoproteins
How much water does articular/hyaline cartilage contain and what use is this?
> 75%
Water is incompressible and so this provides cushioning for the joint
Definition of glycoproteins
Proteins to which oligosaccharide chains are attached i.e. more a protein than a carbohydrate (example; lubricin)
Definition of proteoglycans
Proteins that are heavily glycosated (=a protein core to which one or more GAGs attach) i.e. tend to be more carb than protein
example; aggrecan
Definition of glycosaminoglycans/GAGs
Long unbranched polysaccharides, which are highly polar and thus attract water (e.g. hyaluronic acid)
How does cartilage get nutrients and remove the waste products?
By synovial fluid - produced by the synovial membrane
Cartilage is absent of what
Vessels
Nerves
Lymphatics
Another name for the synovium membrane
Synovium
What produces fluid of the synovium?
Synoviocytes
Features of the synovium that allow its function of transporting nutrients
Rich capillary network
No epithelial lining
Transport function of synovium
Direct exchange of O2, CO2 and metabolites between the blood and the synovial fluid
2 types of Synoviocytes
Type A
Type B
Main producer of synovial fluid is which type of synoviocyte?
Type B
What do type A Synoviocytes do?
Remove debris
Contribute to synovial fluid production
Functions of the synovial fluid
Nutrition of cartilage (Articular, menisci/discs)
Removal of waste products
Lubrication -> less friction -> less wear
Methods of lubrication
Boundary
Hydrodynamic (like aqua planning)
Weeping
What happens during boundary lubrication?
Glycoproteins such as lubricin bind to receptors on an articular surface to form a thin film
What happens during hydrodynamic lubrication?
Surfaces kept apart by liquid pressure -> viscosity changes with load and velocity of movement
What happens during weeping lubrication?
Fluid that is present in the cartilage is squeezed out into the synovial cavity to increase the fluid volume
Function of bursae
Reduce friction
Effects of ageing on cartilage and synovial fluid
Viscosity of synovial fluid increases - slower joint movements - becomes more viscous - reduced lubrication Water content of cartilage decreases - reduced shock absorption SO - less protection of articular surfaces and increased risk of damage
What is Ehler-Danlos syndrome?
An autosomal dominant connective tissue disorder that mostly affects type III collagen. Results in the tissue being more elastic than normal leading to joint hypermobility and increased elasticity of the skin
Presentation of Ehler Danlos syndrome
Elastic, fragile skin
Joint hypermobility; recurrent dislocation
Easy bruising
Aortic regurgitation, MVP and aortic dissection
SAH
Angioid retinal streaks
What is pectus exacavatum?
Breast bone sinks into chest
What condition is pectus exacavatum seen in?
Marfans syndrome
