Joints, Synovial fluid and Cartilage

Question 1

3 types of joints

Answer 1

Fibrous
Cartilaginous
Synovial

Question 2

3 examples of fibrous joints

Answer 2

Periodontal ligament (between tooth and socket)
Cranial sutures
Interosseous membranes (in limbs, between radius and ulna and tibia and fibia)

Question 3

Two types of cartilaginous joints

Answer 3

Primary (synchrondosis)

Secondary (Symphysis)

Question 4

What is primary cartilaginous joints for?

Answer 4

Long bone growth

Question 5

What do primary cartilaginous joints contain?

Answer 5

Only hyaline cartilage

Question 6

In primary cartilaginous joints, where does the growth occur?

Answer 6

In the hyaline cartilage

Question 7

In secondary cartilaginous joints, what do they contain?

Answer 7

Hyaline cartilage AND fibrocartilage

Question 8

Features of a synovial joint

Answer 8

Strong collagen fibres

Synovial cavity filled with synovial fluid

Question 9

Synovial joints may or may not contain what?

Answer 9

Articular discs e.g. TMJ
Ligaments
Bursae

Question 10

Types of synovial joints

Answer 10

Plane
Hinge
Pivot
Condylar (ellipsoid)
Saddle
Ball and socket

Question 11

Which type of cartilage is mechanically the weakest?

Answer 11

Hyaline cartilage

Question 12

What gives a joint its stability?

Answer 12

Shape of articulating surfaces
Capsules and ligaments surrounding joints
Muscles surrounding or crossing joints

Question 13

What is another name for hyaline cartilage?

Answer 13

Articular cartilage

Question 14

Layers of hyaline cartilage

Answer 14

Superficial/tangenital layer
Transitional layer
Deep layer

Question 15

Features of superficial/tangenital layer of hyaline cartilage

Answer 15

Flattened chondocytes (cartilage cells) that produce collagen and glycoproteins 
Collagen fibres same direction due to shear forces -> a lot stronger and resistant to tear

Question 16

Features of the transitional layer of hyaline cartilage

Answer 16

Round chondrocytes that produce proteoglycans such as aggrecan (this is good for binding to/attracting water)

Question 17

What are chondrocytes?

Answer 17

Cartilage cells

Question 18

What do chondrocytes produce?

Answer 18

Collagen

Glycoproteins

Question 19

How much water does articular/hyaline cartilage contain and what use is this?

Answer 19

> 75%

Water is incompressible and so this provides cushioning for the joint

Question 20

Definition of glycoproteins

Answer 20

Proteins to which oligosaccharide chains are attached i.e. more a protein than a carbohydrate (example; lubricin)

Question 21

Definition of proteoglycans

Answer 21

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

Question 22

Definition of glycosaminoglycans/GAGs

Answer 22

Long unbranched polysaccharides, which are highly polar and thus attract water (e.g. hyaluronic acid)

Question 23

How does cartilage get nutrients and remove the waste products?

Answer 23

By synovial fluid - produced by the synovial membrane

Question 24

Cartilage is absent of what

Answer 24

Vessels
Nerves
Lymphatics

Question 25

Another name for the synovium membrane

Answer 25

Synovium

Question 26

What produces fluid of the synovium?

Answer 26

Synoviocytes

Question 27

Features of the synovium that allow its function of transporting nutrients

Answer 27

Rich capillary network | No epithelial lining

Question 28

Transport function of synovium

Answer 28

Direct exchange of O2, CO2 and metabolites between the blood and the synovial fluid

Question 29

2 types of Synoviocytes

Answer 29

Type A | Type B

Question 30

Main producer of synovial fluid is which type of synoviocyte?

Answer 30

Type B

Question 31

What do type A Synoviocytes do?

Answer 31

Remove debris | Contribute to synovial fluid production

Question 32

Functions of the synovial fluid

Answer 32

Nutrition of cartilage (Articular, menisci/discs) Removal of waste products Lubrication -> less friction -> less wear

Question 33

Methods of lubrication

Answer 33

Boundary Hydrodynamic (like aqua planning) Weeping

Question 34

What happens during boundary lubrication?

Answer 34

Glycoproteins such as lubricin bind to receptors on an articular surface to form a thin film

Question 35

What happens during hydrodynamic lubrication?

Answer 35

Surfaces kept apart by liquid pressure -> viscosity changes with load and velocity of movement

Question 36

What happens during weeping lubrication?

Answer 36

Fluid that is present in the cartilage is squeezed out into the synovial cavity to increase the fluid volume

Question 37

Function of bursae

Answer 37

Reduce friction

Question 38

Effects of ageing on cartilage and synovial fluid

Answer 38

``` 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 ```

Question 39

What is Ehler-Danlos syndrome?

Answer 39

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

Question 40

Presentation of Ehler Danlos syndrome

Answer 40

Elastic, fragile skin Joint hypermobility; recurrent dislocation Easy bruising Aortic regurgitation, MVP and aortic dissection SAH Angioid retinal streaks

Question 41

What is pectus exacavatum?

Answer 41

Breast bone sinks into chest

Question 42

What condition is pectus exacavatum seen in?

Answer 42

Marfans syndrome