The Physiology of Cartilage Flashcards

1
Q

What are the three types of cartilage

A

Hyaline (articular), fibrocartilage, elastic cartilage.

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2
Q

Where can hyaline cartilage be found

A

On the surfaces of moveable joints.

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3
Q

Which kind of forces can hyaline cartilage withstand

A

Compressive and tensile forces. It is load bearing.

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4
Q

What is the basketweave structure of collagen in hyaline cartilage

A

Hype two collagen linked by type nine collagen.

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5
Q

What is the appearance of chondrocytes in cartilage

A

They appear flat at the surface and rounded in the deep layers.

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6
Q

What is the role of chondrocytes

A

Chondrocytes are responsible for the synthesis and breakdown of ECM components in cartilage.

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7
Q

What is synthesised and secreted by chondrocytes into the ECM

A

Cartilage specific components such as type II collagen and aggrecan.

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8
Q

Are chondrocytes stable or unstable

A

Chondrocytes are unstable cells as they want to becomes fibroblasts - this would allow them to synthesise type I collagen and small PGs as opposed to type II collagen and aggrecan.

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9
Q

What type of enzymes are secreted by chondrocytes

A

Degradative enzymes such as collagenases, matrix metalloproteinases cathepsins.

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10
Q

Where can fibrocartilage be found

A

The meniscus and the intervertebral disc.

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11
Q

What are the roles of fibrocartilage

A

Support, prevention of bone to bone contact, spread of the load and limitation of movement.

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12
Q

What forces can fibrocartilage withstand

A

Tensile and compressive forces.

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13
Q

What is the orientation of collagen fibres in fibrocartilage

A

Collagen fibres are thick and have a clear parallel orientation and structure. Cells are often in rows.

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14
Q

Which types of cells - fibroblasts or chondrocytes - are present mostly in fibrocartilage

A

It is mainly fibroblasts however there are some chondrocytes.

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15
Q

Where can elastic cartilage be found

A

The auricle of the ear and the epiglottis

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16
Q

What is present in high contents in elastic cartilage

A

Elastin fibres

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17
Q

How does elastin in elastic cartilage show up in histology

A

Elastin shows up black in histology

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18
Q

What type of movement does elastic cartilage allow

A

Elastic cartilage is very good for flexible movement however is not good for load bearing.

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19
Q

Which types of cell synthesise elastin

A

Fibroblasts.

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20
Q

What are the roles of articular cartilage

A

To absorb and distribute load and protect the ends of bones. Along with synovial fluid it also creates a low friction surface for articulating joints.

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21
Q

What does synovial fluid contain

A

Hyaluronic acid.

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22
Q

Which cells produce synovial fluid

A

Synoviocytes of the synovial membrane.

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23
Q

What is the role of synovial fluid

A

Synovial fluid is the primary source of nutrition and removal of waste for cartilage cells.

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24
Q

What is the consistency of synovial fluid

A

When the joint is immobile, synovial fluid is viscous. When mobile, the viscosity is reduced to lubricate the joint.

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25
Q

What is the name of a condition in which the immune system attacks the synovium of joints

A

Rheumatoid arthritis.

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26
Q

What do connective tissues respond to

A

Their mechanical environment - they are not inert but living.

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27
Q

What makes cartilage thicker

A

Load bearing cartilage is ticker and stronger than non-load bearing cartilage.

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28
Q

What happens to cartilage in immobilised joints

A

Cartilage is lost because the cells are not receiving signals from the mechanical environment.

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29
Q

What is Wolff’s Law

A

“Form follows function” - if there is different load/mechanical stimulation on a joint this will affect its appearance.

30
Q

How much movement is required per day to avoid disuse OP

A

Four cycles of strain per day - very little strain is needed to avoid disuse OP.

31
Q

What is the function of a tendon

A

Connects muscle to bone

32
Q

What is the function of a ligament

A

Connects bone to bone.

33
Q

Where in a tendon may there be more proteoglycans

A

Where there is more compressive force applied, so when the tendon crosses a bone. If there is only tensile force there will be less PGs.

34
Q

Which has a higher percentage of collagen, ligaments or tendons?

A

Tendons have a higher percentage of collagen compared to ligaments (more tensile forces)

35
Q

Which has a higher percentage of proteoglycans, ligaments or tendons?

A

Ligaments have a higher percentage of proteoglycans compared to tendons (more compressive forces)

36
Q

Which has more elastin, tendons or ligaments

A

Ligaments

37
Q

What type of collagen has a higher percentage in both tendons and ligaments

A

Type I collagen.

38
Q

What is cartilage thickness dependent on

A

Prevailing load

39
Q

What is the result of excess or impact load

A

Matric damage and chondrocyte death.

40
Q

What is the ratio of synthesis to break down in normal dynamic loading

A

Synthesis = breakdown normally

41
Q

What is the relationship between synthesis and breakdown if there is greater loading

A

There is more synthesis than breakdown (synthesis > breakdown)

42
Q

What is the relationship between synthesis and breakdown if there is less loading

A

There is more breakdown than synthesis (breakdown > synthesis)

43
Q

Which cells control matrix synthesis and breakdown

A

Chondrocytes,

44
Q

What are the two types of load on chondrocytes

A

Static and dynamic.

45
Q

What is the relationship between static load and synthesis

A

Static load depresses synthesis.

46
Q

What is the relationship between dynamic load and synthesis

A

Dynamic load stimulates synthesis.

47
Q

What is mechanotransduction

A

The link between the mechanical environment of the cell and the cells response.

48
Q

How is cartilage adapted to withstand load

A

It does not contain any vulnerable structures - it is avascular, aneural, alymphatic so blood vessels, nerves and lymphatic vessels cannot be damaged, and there is low cell density to cells do not become compressed.

49
Q

What are the four principle components of articular cartilage

A

1) collagens
2) proteoglycans
3) interstitial fluid
4) chondrocytes.

50
Q

What is the main type of collagen in hyaline cartilage

A

Type II

51
Q

What is the main type of collagen in fibrocartilage

A

Type I

52
Q

What type of collagen stabilises the basketweave structure of hyaline cartilage

A

Type 9

53
Q

What is an example of a proteoglycan

A

Aggrecan

54
Q

What is aggrecan composed of

A

Glucosaminoglycans (GAGs)

55
Q

What is the charge of proteoglycans

A

Negatively charged

56
Q

What does the negative charge of proteoglycans bring about

A

The negative charge attracts cations, particularly sodium ions, to the cartilage. This brings water with it and causes the proteoglycans to swell.

57
Q

To what percentage of their total do proteoglycans swell when in the basketweave structure

A

20%

58
Q

What is the result of papain treatment on cartilage

A

It causes chondrocytes to produce degragatory enzymes which damages proteoglycans.

59
Q

What is the string and balloon model of articular cartilage

A

Type two collagen is stabilised by type nine collagen. The basketweave structure contains partially inflated PGs. There is lots of positive pressure.

60
Q

What happens to the PGs if the collagen structure becomes damaged

A

The PGs inflate more.

61
Q

What is the composition of the interstitial fluid dependent on

A

Proteoglycans as these are negatively charged so attract positive cations and repel negative anions.

62
Q

What causes the composition of interstitial fluid to change

A

Different loads. It changes during static load as fluid is extruded.

63
Q

What is the single resident cell type in hyaline cartilage

A

Chondrocytes.

64
Q

When do chondrocytes proliferate

A

In the late stages of OA. In normal, healthy cartilage there is no chondrocyte division.

65
Q

What is the rate of turnover of articular cartilage

A

Very slow.

66
Q

Why would osteoarthritis be better termed osteoarthrosis

A

Because the condition is not initially inflammatory - it only becomes inflammatory in the late stages.

67
Q

Is osteoarthritis considered a disease or a syndrome

A

A syndrome because it is a multifactorial condition - there are many factors which contribute.

68
Q

What are the treatments for osteoarthritis

A
  • Education
  • “Prescription of exercise”
  • Weight loss
69
Q

What is the first macroscopic event in OA

A

Cartilage swelling - the cartilage becomes more hydrated.

70
Q

How is OA cartilage different from aged cartilage

A

OA cartilage becomes more hydrated while age causes cartilage to become dehydrated.

71
Q

Why does cartilage become more hydrated in OA

A

Because there is damage to the collagen basketweave structure which means more water is allowed to enter and the proteoglycans swell more. The cartilage becomes mechanically weakened.