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LOCO2 > Osteoarthritis > Flashcards

Osteoarthritis Flashcards

1
Q

What is the role of articular cartilage in a synovial joint? [2]

What type of cartilage is present? [1]

A

reduces friction and help absorb impacts / shock absorber so that bones do not get as impacted

hyaline cartilage

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2
Q

Label A-E

A

A: calcified cartilage
B: chondrocytes
C: tide line
D: hyaline cartilage
E: articular surface

Hyaline cartilage: non-calcified
Deeper layers of cartilage are calcified: darker
Seperated via a tide mark

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3
Q

Describe blood supply to articular cartilage [1]

Describe innervation to articular cartilage [1]

A

avasuclar - relies on synovial fluid to bring in o2 and glucose to supply chondrocytes

No innvervation

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4
Q

Articular cartilage

Label A-E

A

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

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5
Q

which layer in articular cartilage do chondrocytes hypertrophy and form columns

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

which layer in articular cartilage do chondrocytes hypertrophy and form columns

A: tangenitial layer
B: transitional layer
C: radial layer / deep layer
D: calcified cartilage
E: bone

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6
Q

Which layer is this

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

Which layer is this

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

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7
Q

Which layer is this

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

Which layer is this

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

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8
Q

Which layer do chondrocytes die in?

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

Which layer do chondrocytes die in?

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage

Leave an empty hole, releasing their extracellular contents into the matrix which triggers calcification. Calcified cartilage is eventually digested by osteoclasts and replaced with bone

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9
Q

Which layer is this

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

Which layer is this

A: tangenitial layer
B: transitional layer
C: radial layer / deep layer
D: calcified cartilage
E: bone

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10
Q

Which layer of articular cartilage are ER and golgi apparatus prominent in chondrocytes

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

Which layer of articular cartilage are ER and golgi apparatus prominent in chondrocytes

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

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11
Q

Why do chondrocytes in articular cartilage have a low number of mitochondria?

A

Low number of mitochondria – low oxygen consumption

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12
Q

The main type of collagen in articular cartilage is:

Type 1
Type 2
Type 3
Type 4

A

The main type of collagen in articular cartilage is:

Type 1
Type 2
Type 3
Type 4

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13
Q

Type X collagen is also present in articular collagen. Which layer is this mainly in? [1]

A

Calcified deeper layers

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14
Q

The ECM of cartilage is produced by the chondrocytes and contains up to 80%

Cartilage
Bone
Water
Aggrecans
Hyaluronic acid

A

The ECM of cartilage is produced by the chondrocytes and contains up to 80%

Cartilage
Bone
Water
Aggrecans
Hyaluronic acid

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15
Q

Describe the differences in structure of collagen fibres in articular capsule [3]

Superficially
Intermediate
Deep

Which levels are compressable? [2]

A

Superficially
* parallel with surface highest tensile properties mainly allows gliding

Intermediate
* criss-crossed oblique allows compression and protects structure

Deep:
* perpendicular to surface follow stacks of chondrocytes to protect them from compression

Superficially & Intermediate compressable

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16
Q

Explain the structure of proteoglycans found in articular carticlage [2]

A

Aggrecan is the side chain made from multiple other GAG side chains on a hyaloronic acid

Negatively charged: attracts water from synovial fluid into the articular cartialge. Keeps the structure hydrated

17
Q

Osteoarthritis

Which genes increase risk of severe OA? [3]

dont learn

A

COL2A1: makes type 2 collagen
IL-1R1: linked to hand, hip and knee OA
PTGS2/PLA2G4A – knee and spine OA

18
Q

What is an osteophyte [1]?

A

indicated with white arrow

that is sticking out and pushing into the synovial membrane and articular capsule, which will irritate it. You can also see complete loss of cartilage in some areas here.

19
Q

Describe the MoA for the release of AN the role of proinflammatory cytokines in the pathophysiology of OA [3]

A

Once the chondrocytes become damaged, they release pro-inflammatory cytokines which causes inflammatory response in the rest of the joint:

  • increase the production of matrix metalloproteinases and ADAMT-4
  • reduce aggrecan production and type 2 collagen production
  • overall cartilage degradation
  • Local inflammation: IL-1, IL-6, TNF
20
Q
A
21
Q

Describe steps of OA to synovitis [3]

A

Bone and cartilage damaged
Inflammation
Synovitis (secondary to established bone and cartilage pathology); major cause of pain and loss of function)
-

22
Q

Describe key changes in pathology of OA

A
  • Repetitive excess mechanical loading is what leads to stress-induced signals in the articular cartilage
  • Chondrocyte cloning and hypertrophy
  • tidemark duplication, followed by osteophyte formation, bone microfractures, angiogenesis
23
Q

Name a gene that is known to contribute to OA pathogensis [1]

What is the effect of losing this gene [3]

A

HMGB2: high mobility group protein 2 (chromatin protein)

Loss of HMGB2, leads to superficial zone cell death, loss of progenitor cells, and reduced synthesis of ECM components

24
Q

Macroscopically articular cartilage goes through 3 phases of degeneration. What are they? [3]

A

Fibrillation: rougher with frilly edges, compared to the usual nice and smooth appearance
Erosion and cracking: these cracks bigger and bigger due to the hydronic action in the joint
Eburnation:
* Complete loss of cartilage
* Completely exposed bone becomes polished

25
Q

FYI each stage of breakdown of cart

A
26
Q

Microscopically what happens in pathogenesis of OA? [3]

A

Chondrocyte necrosis - more in superficial layers. Dead cells not removed: ECM contamination

Focal clumps or clones of chondrocytes
* Increased local proliferation
* Large Isogenic clusters
* (The middle zone normally contains evenly spread out layers of chondrocytes, yet in osteoarthritis there are isogenic clusters/focal clumps of chondrocytes due to increased local proliferation where they group together in areas)

Change from type II to type I cartilage
* Reduces thickness of articular cartilage & Duplicated tidemark

27
Q

What is happening in this slide of OA? [1]

A

Conversion of type II to type I collagen

28
Q

Early OA is characterised by: [2]

Late OA is characterised by: [2]

A

Early OA:
* loss of superficial zone and changes to the ECM of articular cartilage
* cell clusters emerge

Late OA
* continued loss of ECM
* chondrocyte hypertrophy

29
Q

What happens biochemically in pathogenesis in osteoarthritis [4]

A
  • In early stages of OA articular cartilage thickens and swells - increased water
  • But loss of proteoglycans make it less compressible
  • Water moves in and out faster
  • Collagen network breaks down as enzymes are released from stressed chondrocytes and synovial membrane cells
30
Q

Which area of articular cartilage does OA initiate in?

A: tangenitial layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

A

Which area of articular cartilage does OA initiate in?

A: tangenitial layer / superifical layer
B: transitional layer
C: radial layer
D: calcified cartilage
E: bone

31
Q

Describe final stage; of OA impacting the subchondral bone

A

As articular cartilage is eroded, the underlying bone is exposed:
* There is microfractures of the trabeculae,
* increased osteoblastic activity and new bone formation
* resulting in subchondral sclerosis
* The surface also undergoes focal pressure necrosis, which leads to subarticular cysts forming.
* There is vascular engorgement, which slows blood flow, and there is bone marrow oedema.

LOCO2 (58 decks)

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