Joints Synovial fluid and cartilage

Question 1

Types of fibrous joints with an example of each?

Answer 1

> Suture - Bones of the cranium
Periodontal - Holds tooth in socket
Interosseus - Joint held together by ligament, e.g. the fibula and tibia

Question 2

Suture joint?

Answer 2

A fibrous joint held together with short, interconnecting fibres, and bone edges interlock, found only in the skull

Question 3

Interosseus joint?

Answer 3

A fibrous joint held together by a ligament. Fibrous tissue can vary in length but is longer than sutures

Question 4

Periodontal joint?

Answer 4

Peg-in-socket fibrous joint. Periodontal ligament holds tooth in socket

Question 5

Primary cartilaginous joint?

Answer 5

• Synchondrosis
• Only hyaline cartilage
• Examples = Epiphyseal plate, sternomanubrial joint and first rib and sternum

Question 6

Secondary cartilaginous joint

Answer 6

• Symphysis
• Hyaline and fibrocartilage
• Examples = Intervertebral joints and pubic symphysis

Question 7

What are the common features of a synovial joint?

Answer 7

1) Fibrous capsule
2) Synovial membrane
3) Articular cartilage
4) Synovial cavity (fluid-filled)

May also contain:

• Articular discs
• Ligaments
• Bursae

Question 8

Examples of synovial joint types?

Answer 8

> Plane - Vertebrae
> Hinge - Elbow
> Pivot - Radio-ulnar
> Condylar - Radiocarpal 
> Saddle - thumb 
> Ball and socket - Shoulder

Question 9

What determines joint stability?

Answer 9

> Shape of articulating surfaces
Capsule and ligaments
Muscles

Question 10

Which cartilage is present in a synovial joint?

Answer 10

Hyaline and fibrocartilage

Question 11

What is the “make up” of hyaline (Articular) cartilage?

Answer 11

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

Question 12

What does the superficial layer of articular (Hyaline) cartilage produce?

Answer 12

Collagen and glycoproteins e.g. lubricin

Question 13

What does the transitional layer of articular (Hyaline) cartilage produce?

Answer 13

Proteoglycans such as aggrecan

Question 14

What are glycoproteins?

Answer 14

> Example - Lubricin
Proteins to which oligosaccharide chains are attached
More protein than carbohydrate

Question 15

What are proteoglycans?

Answer 15

> Example - Aggrecan
Protein that are heavily glycosylated. A protein core to which one or more GAGs attach
Tend to be more carb than protein

Question 16

What are glycosaminoglycans?

Answer 16

> Example - Hyaluronic acid

> Long unbranched polysaccharides, which are highly polar and thus attract water

Question 17

Are glycosaminoglycans hydrophobic or -phillic and why?

Answer 17

Hydrophillic as they are highly polar

Question 18

How thick is the average cartilage?

Answer 18

2-3mm

Question 19

How thick is interphalangeal cartilage?

Answer 19

1 mm

Question 20

How thick is patella cartilage?

Answer 20

5-6 mm

Question 21

What does cartilage lack?

Answer 21

• Avascular
• Aneural
• Alymphatic

Question 22

What produced synovial fluid and where?

Answer 22

Produced by synoviocytes in the synovium

Question 23

What is the Synvoium composed of?

Answer 23

> Synoviocytes which produce synovial fluid
Rich capillary network
No epithelial lining

Question 24

What is the role of the synovium?

Answer 24

Direct exchange of oxygen, carbon dioxide and metabolites between blood and synovial fluid

Question 25

Type A synoviocytes?

Answer 25

> Look like macrophages
Remove debris
Contribute to synovial fluid production

Question 26

Type B synoviocytes?

Answer 26

> Fibroblast like

> Main producer of synovial fluid

Question 27

Density of synovial fluid?

Answer 27

Viscous fluid

Question 28

What is synovial fluid composed of?

Answer 28

> Hyaluronic acid and lubricin

> Fluid component, from the blood plasma

Question 29

Volume of synovial fluid?

Answer 29

Small volumes e.g. knee joint = 0.5ml

Question 30

Turnover of synovial fluid?

Answer 30

Rapid turnover = 2 hours

Question 31

What is the role of synovial fluid?

Answer 31

1) Nutrition of cartilage
2) Removal of waste products
3) Lubrication –> less friction
- -> Less wear

Question 32

How does synovial fluid lubricate?

Answer 32

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

Question 33

What is the coefficient of friction in a synovial joint?

Answer 33

0.002-0.2

Question 34

What is the role of a bursae?

Answer 34

A fluid filled pad that acts to reduce friction within the synovial membrane

Question 35

What happens to the viscosity of synovial fluid as you age, what is the result of this?

Answer 35

Viscosity increase:

• Slower joint movements
• Reduced lubrication

Question 36

What happens to the water content of cartilage within synovial joints as you age, what is the result of this?

Answer 36

Water content of cartilage is decreased = Reduced shock absorption

Question 37

What occurs within synovial joints as we age, what is the result of this?

Answer 37

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

Question 38

What occur as a result of osteoarthritis?

Answer 38

• Bone spurs

- Narrowing of intervertebral discs