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LOCO > 6 - Normal and Abnormal Joints, Pathogenesis of OA > Flashcards

6 - Normal and Abnormal Joints, Pathogenesis of OA Flashcards

1
Q

What is the anatomy of a synovial joint

A

Synovial membrane then fibrous capsule which surround synovial fluid

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2
Q

Function of synovial fluid

A

Provides hydration and nutrition to the joint

Allows fricitonless movement

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3
Q

What is the articular cartilage and why is it there

A

Hyaline cartilage which attaches to the end of a bone to reduce friction and absorb impacts

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4
Q

What makes the articular cartilage

A

Chondrocytes

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5
Q

The role of articular cartilage

A

Elastic
Resilient
Acts as a shock absorber

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6
Q

What does the ECM of the articular cartilage consist of

A

Collagen

Proteoglycans

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7
Q

What are the characteristics of chondrocytes in the superficial/tangential zone

A

Flattened
Smaller
Greater in density

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8
Q

What are the characteristics of chondrocytes in the Intermediate/transitional zone

A

Rounder
Larger
Sparser

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9
Q

What are the characteristics of chondrocytes in the Deep/Radial zone

A

Stacked in columns

Most rounded

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10
Q

What is the function of chondrocytes

A

Regulate and establish micro-environment (the ECM)

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11
Q

In which layer is there prominent endoplasmic reticulum and golgi apparatus? why?

A

Deep layer

For protein synthesis and sulphation of mucopolysaccharrides that form proteoglycan side chains

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12
Q

What colour stain are proteoglycans and what is their charge

A

Red
Negative charge
attract water

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13
Q

What is the ECM of the articular cartilage made up of

A 
80% water
Collagen Type 2 mainly 
Proteoglycans
Lack of blood + lymph
No nerve supply
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14
Q

What does the collagenT2 do in articular cartilage?

A

Makes pockets filed with proteoglycans

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15
Q

What is the function of proteoglycans

A

Draw water into the cartilage
Regulates compressibility
Water comes out when you move

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16
Q

What is the orientation of collagen fibres superficially?

A

Parallel with the surface
gives highest tensile properties
Allows gliding

17
Q

What is the orientation of collagen fibres intermediately?

A

Criss-crossed oblique allows compression

18
Q

What is the orientation of collagen fibres Deep?

A

Perpendicular to surface follow stacks of chondrocytes

19
Q

What is the main collagen type in the cartilage?

A

Collagen type 2 (90-95%)

Mainly in superficial layers

20
Q

Where is collagen type 10 found in the cartilage?

A

Calcified, deeper layers

21
Q

Other types of collagen in the cartilage?

A

2,9, 10, 11

22
Q

Function of collagen in the cartilage

A

To hold proteoglycans in place

23
Q

What percentage of dry weight is collagen and proteoglycans

A 
Collagen = 40-70%
PG = 15-40%
24
Q

Features of proteoglycans

A

Highly hydrophillic
Negatively charged
Traps water

25
Q

What is a proteoglycan made up of

A

Core protein

Glycosaminoglycan side chains

26
Q

What is the core protein in a proteoglycan

A

Hyaluronan

27
Q

What are GAGs and some examples?

A

Linear polysaccharides of repeating disaccharide units

  • Keratin Sulphate (KS)
  • Chondroitin Sulphate (CS)
28
Q

Risk factors for Osteoarthritis

A 
Increasing age
Genetics
Diet
Infection
High BMI
Physical activity levels
29
Q

What causes the pain and loss of function in osteoarthritis

A

Damage to chondrocytes

Causes proinflammatory cytokines to be released from chondrocytes

30
Q

What is the function of HMGB2

A

High Mobility Group Protein 2

- regulates DNA of chondrocytes wrapping around histones

31
Q

Where is HMGB2 expressed and what does it do there

A

Superficial zone chondrocytes
Supports chondrocyte survival
regulates specific differentiation status of superficial zone cells (inc progenitor cells)

32
Q

What does loss of HMGB2 cause

A

Loss of progenitor cells
Death of superfical zone
reduced synthesis of ECM components

33
Q

3 Phases of degeneration the articular cartilage goes through in osteoarthritis

A

1) Fibrillation - small cracks on the surface
2) Erosion and cracking
3) Eburnation - complete loss of cartilage, exposed bone becomes polished

34
Q

Microscopic pathology of osteoarthritis

A

Chondrocyte necrosis
Clumps of chondrocytes rather than columns
Change from hyaline to fibrocartilage (Type 1 not 2), reduced thickness

35
Q

What occurs biochemically to the cartilage

A

Collagen broken down
Cartilage thickens and swells
Loss of proteoglycans so less compressable

36
Q

Why can there be subchondral sclerosis in osteoarthritis

A

Bone tries to make itself harder to deal with the lack of articular cartilage
Also subarticular cysts

37
Q

Treatment for early osteoarthritis

A

Cartilage stem/progenitor cells (CSPCs) could help regenerate joint resurfacing,
o ECM production and chondroprotection

LOCO (25 decks)

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