Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 2 Loco > 7. Pathogenesis of osteoarthritis - Lesley Robson > Flashcards

7. Pathogenesis of osteoarthritis - Lesley Robson Flashcards

1
Q

Give the structure of a synovial joint

A

Two bones almost meet each other with articular (hyaline) cartilage at the ends (ends of the bones are capped with articular cartilage
Synovial cavity - filled with synovial fluid
Synovial membrane surrounds this
All contained within the articular capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the function of synovial fluid?

A

Acts as a lubricant to produce almost frictionless, smooth movement of the joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the articular capsule composed of?

A

Synovial membrane

Fibrous capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is articular cartilage and where is it found in a joint capsule?

A

Hyaline cartilage

Caps the ends of bones in synovial joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the function of the articular cartilage? x2

A

Reduces friction and increase range of movement

Shock absorber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does hyaline cartilage carry out it’s function?

A

This provides a smooth, slippery surface at the ends of the bones to reduce friction and to help absorb impacts

Articular hyaline cartilage contains a lot of water (remember that bone is only 5% water) so acts as a sponge and a shock absorber to protect the underlying bone from damage (the weight and force placed on bone is absorbed by the high water content of the hyaline cartilage)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a ‘tide mark’?

A

This is where the articular hyaline cartilage merges with the underlying bone - the cartilage is calcified to merge and this leaves the mark

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why does hyaline cartilage not show on an x-ray and what will be seen instead?

A

X-ray only images dense tissue i.e. where the calcium salts are - so will show the bone but not the articular cartilage

X-ray will show an apparent space where the articular cartilage actually lies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the layers of articular cartilage?

A 
Superficial/tangenital zone 
Middle/transitional zone 
Deep/radial zone 
Tide mark 
Calcified zone 
Subchondral zone 
Cancellous bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the appearance of the chondrocytes and the collagen orientation of the superficial/tangenital zone

A

Small, reserve cells - these sit on the surface of the cartilage - these cells are very slowly proliferating - flat and small and in greater density

Collagen fibres are parallel with the surface of the cartilage - nice smooth surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the appearance of the chondrocytes and the collagen orientation of the medial/transitional zone

A

These cells increase in size - rounder larger and sparser

Collagen fibres are haphazard and in crisscross arrangement - forms pockets where proteoglycans sit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the appearance of the chondrocytes and the collagen orientation of the deep/radial zone

A

These cells are larger - hypertrophied and start to produce alkaline vesicles
The chondrocytes stack up as they have proliferated

Cartilage then merges with the underlying bone and there is a tidemark

Collagen fibres are perpendicular to the surface and follows the stacks of the chondrocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the cells found in cartilage?

A

Chondrocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the function of chondrocytes?

A

These regulate both the synthetic and the catabolic processes

Are continually making more ECM i.e. proteoglycans and also removing the old and damaged proteoglycans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where are chondrocytes found in the hyaline/articular cartilage?

A

Each chondrocyte sits in its own lacuna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Chondrocytes have low levels of what organelle and why?

A

Low number of mitochondria - low energy/O2 consumption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Function of negatively proteoglycans of the articular cartilage is?

A

Draws water into the articular cartilage from the surrounding synovial fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the role of the chondrocytes in the superficial zone of cartilage?

A

These act as reserve cells - these add to the deeper layer when and if required

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the ECM of cartilage composed of?

A

80% water
Collagen type II

No neurovasculature or lymphatic vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What cells produce the ECM of cartilage?

A

Chondrocytes

Sit in lacunae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What types of collagen are found in the ECM of cartilage?

A

Mainly type II

Very small levels of type X - this is found in higher levels in the calcified deeper levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What collagen type is particularly found in the deeper, calcified layer of the cartilage?

A

Collagen type X

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where do proteoglycans sit in cartilage?

A

Transitional layer in pockets produced from the transitional structure of the collagen fibres in this layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do proteoglycans exist in cartilage?

What is the collagen type that holds the proteoglycans?

A

Proteoglycans are present as aggregates - not on their own

Collagen type II holds PGs in place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the main characteristic of proteoglycans?

A

Have negative charge (can trap water)

26
Q

What is the main proteoglycan in the body?

A

Aggrecan

27
Q

What is the main pathology in osteoarthritis (OA)?

A

Degeneration of the articular (hyaline) cartilage

28
Q

What are the main joints affected in OA?

A

The weight bearing joints - the ones under the most stress and strain e.g. knees

29
Q

How does the bone respond when there is a loss of articular cartilage in OA?

What is the problem with this?

A

The bone responds by producing more bone in an attempt to heal itself

This rubs and irritates the synovial membrane - irritation, pain, discomfort

30
Q

What are the risk factors for OA?

A 
Increased age 
Female gender 
Racial/ethnic factors 
Genetics 
Previous damage  
Injurious physical activities 
Obesity (increased strain on joints)
31
Q

What inflammation occurs in OA?

A

Local inflammation - release of inflammatory cytokines
Inflammatory cycle

This results in even further reduction of ECM production

32
Q

Why does OA occur? x3

A

Age - chondrocytes are getting older and cannot produce as much protein or as good quality protein

Mechanical stress throughout life - increased ROS that chondrocytes are exposed to - not as healthy

Stress induced signals - weakens and reduces quality of the chondrocytes

33
Q

Lack of what protein causes early onset OA?

What is the protein involved in the genetic aspect of OA?

A

HMGB2 - High mobility group protein 2

34
Q

Where is HMGB2 expressed?

A

Expressed in the superficial zone chondrocytes and supports survival of these cells

35
Q

What are the three stages of degeneration of the articular cartilage in OA?

A

Fibrillation
Erosion and cracking
Eburnation

36
Q

What happens in fibrillation of articular cartilage?

A

The surface of the cartilage is no longer smooth or flat - becomes frilly with frilly edges to it

37
Q

What happens in erosion and cracking of articular cartilage?

A

Slight cracks appear in the cartilage and the synovial fluid thickens
High hydrolic pressure is present on the joint upon movement - fluid is forced into the cracks and causes them to widen further

38
Q

What happens in eburnation of articular cartilage?

A

The cracks of the cartilage widen to such a great extent that the cartilage breaks off and there is exposure of the underlying bone

39
Q

What happens to chondrocytes in OA?

A

Chondrocyte necrosis - in all layers due to high levels of stress

40
Q

In which layer is chondrocyte necrosis the most obvious in OA?

A

In the superficial layer

41
Q

There is a switch of collagen type II to what type of collagen as the articular cartilage breaks down?

A

Collage type I - more like fibrocartilage and cannot do its job

42
Q

What happens to the structure of chondrocytes in the deep layer during degeneration of cartilage in OA?

A

Remaining chondrocytes in the deep layer proliferate at a very high rate to try and compensate for the loss of superficial layers

High number of chondrocytes - form clusters rather than the organised stacks

43
Q

Why does articular cartilage thicken and soften in early stages of OA?

A

There is an initial increase in the water entering the cartilage as the collagen pores get bigger as the fibres start to get damaged - the water is not held and as it leaks out it damages even more collagen fibres

44
Q

What is the name given to softening cartilage?

A

Chondromalacia

45
Q

What happens to the cartilage once it has softens?

A

Softens and then undergoes fibrillation

46
Q

What happens to proteoglycans as we age?

A

As ageing occurs, the proteoglycans get smaller and have less side chains attached to them - cannot hold as much water in the cartilage ECM - water moves in and out and damages the collagen fibres

47
Q

What is meant by ‘osteophyte’?

A

Degeneration of artilcular cartilage results in exposed bone - this exposed bone starts to produce even more bone and this is the ‘osteocyte’

48
Q

What is subchondral sclerosis and why does this occur?

A

This is thickening of the bone under the cartilage

Sclerosis - pathological thickening of tissue

49
Q

Why do trabeculae fractures occur in OA?

A

There is damage to the exposed bone and synovial fluid seeps into the exposed trabeculae structure and causes cracks

50
Q

Proteoglycans are in which layer of articular cartilage?

A

Middle transitional zone

51
Q

Hyaline cartilage has high or low coefficient of friction?

A

Low

52
Q

Chondrocytes make up what percentage of the articular cartilage?

A

<5%

53
Q

Chondrocytes in the radial/deep layer of articular cartilage have high levels of what two organelles?

A

Golgi bodies

Endoplasmic reticulum

54
Q

Function of specialised organelles in the radial layer of articular cartialge is?

A

Production of proteoglycan side chains

55
Q

Proteoglycan side chains are positively or negatively charged?

A

Negatively

56
Q

Function of negatively charged proteoglycan side chains in articular cartilage?

A

Draws water out from the synovial fluid into the articular cartilage

57
Q

Main side chain of proteoglycans in the articular cartilage are?

A

GAGs polysaccharide units

58
Q

Two main GAG proteoglycans that attach to aggrecan proteoglycan are?

A

Keratin sulphate

Chondroitin sulphate

59
Q

Main protein that composes proteoglycans is?

A

Hyaluronic acid

60
Q

Consequences of lack of HMGB2 x3

A

S of chondrocytes in the superficial zone
Loss of progenitor cells
Reduced synthesis of ECM components

61
Q

Subchondral bone is exposed in which stage of cartilage degeneration in OA?

A

Eburnation

62
Q

As well as osteophytes, what else may form in response to the articular degeneration in OA?

A

Subchondral cysts

Year 2 Loco (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions