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Year 2 Physiology > Physiology of Joints > Flashcards

Physiology of Joints Flashcards

1
Q

3 types of joints?

A
  1. Synovial (AKA diarthrosis)
  2. Fibrous (AKA synarthrosis)
  3. Cartilaginous (AKA amphiarthrosis)
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2
Q

What are fibrous joints?

A

Bones are united by fibrous tissue and so no movement is allowed, e.g: bones of the skull in adults

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3
Q

What are cartilaginous joints?

A

Bones are united by cartilage and allow limited movement, e.g: intervertebral discs, pubic symphisis, part of the sacroiliac joint and the costochondral joints

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4
Q

What are synovial joints?

A

Bones are separated by a cavity, filled with synovial fluid, and united by a fibrous capsule and other extra-articular structures, e.g: ligaments, tendons and bursae

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5
Q

Describe the synovial membrane

A

Lines the inner aspect of the fibrous capsule; it is a vascular connective tissue, with capillary networks and lymphatics

Fibroblasts (synovial cells) produce synovial fluid

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6
Q

2 types of synovial joints?

A

Simple synovial joint (one pair of articular surfaces), e.g: metacarpophalangeal joint

Compound synovial joint (more than one pair of articular surfaces), e.g: elbow joint

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7
Q

Functions of joints?

A

Provide structural support and allow purposeful motion of the MSK system

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8
Q

3 roles of joints during purposeful motion?

A

Stress distribution

Confer stability

Joint lubrication

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9
Q

How do joints confer stability?

A

Shape of the articular component, e.g: the hip joint

Ligaments provide a second major stabilising force

Synovial fluid acts as an adhesive seal, freely permitting sliding motion between cartilaginous surfaces

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10
Q

What provides joint lubrication?

A

Cartilage interstitial fluid

Synovium (the synovial membrane) is a polymer of disaccharides and is lubricated with hyaluronic acid (mucin)

Synovium-derived lubrcin (glycoprotein)

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11
Q

Functions of synovial fluid?

A
  • Lubricates joint
  • Facilitates joint movements, reducing friction
  • Helps minimise wear-and-tear via lubrication
  • Aids in nutrition of articular cartilage
  • Supplies chondrocytes with O2 and nutrients and removes CO2 and waste products
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12
Q

The synovial fluid not a static pool. How?

A

Continuously replenished and absorbed by the synovial membrane

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13
Q

Thickness of synovial fluid?

A

High viscosity due to hyaluronic acid (mucin), which is produced by the synovial cells

Viscosity varies with joint movement but this is impaired in a diseased joint

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14
Q

Constituents of the synovial fluid?

A
  • Hyaluronic acid (mucin)
  • Uric acid - derived from dialysis of blood plasma
  • Few cells (mainly mononuclear leukocytes)
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15
Q

How do the viscosity and elasticity of the synovial fluid vary?

A

Rapid movement:

Decreased viscosity

Increased elasticity

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16
Q

Appearance of synovial fluid in different scenarios?

A

Normal: viscous, clear and colourless

Red: traumatic synovial tap and in haemorrhagic arthritis

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17
Q

Leukocytes in synovial fluid?

A

< 200 WBC/mm3

Of this, <25/mm3 comprises polymorph cells

18
Q

When does WBC increase in synovial fluid?

A

Inflammatory and septic arthritis

19
Q

Compare normal, inflammatory and septic synovial fluid in the following aspects:

Viscosity

Colour

Clarity

Total WBC

PMN leukocytes ?

A
20
Q

Describe the synovial fluid in each of the test tubes

A

A: normal synovial fluid that is viscous and clear

B: from joint with mild synovial inflammation

C: from joint with mild synovial inflammation; blood stain is caused by trauma

D: from a severely inflamed joint; thin and opaque due to a very high polymorph count

21
Q

Main functions of articular cartilage?

A
  • Provides a low friction lubricated gliding surface to help prevent wear-and-tear of joints
  • Distributes contact pressure to subchondral bone
22
Q

How are the mechanical properties of cartilage determined?

A

Composition of cartilage ECM and the interaction between the fluid and solid phase plays a role in determining mechanical properties of cartilage

23
Q

Name the different zones of the articular cartilage?

A
24
Q

How do the different zones of articular cartilage vary?

A

Organisation of collagen fibres

Relative content of cartilage components

25
Q

Type of cartilage that is normally articular?

A

Hyaline (elastic and sponge-like)

26
Q

Components of hyaline cartilage?

A

Extracellular matrix (ECM):

  • Water (70%) - maintain resiliency of tissue and contribute to nutrition and lubrication
  • Collagen (20%) - mainly type II; contributes to the elastic behaviour of cartilage, tensile stiffness and strength
  • Proteoglycans (10%) - provides compressive properties assoc. with load-bearing
27
Q

Variation in water content of articular cartilage?

A

Uneven distribution (most is near the articular surface)

Cartilage water content decreases with AGE

28
Q

Types of proteoglycan in articular cartilage?

A

Mainly GAGs, e.g: chondroitin sulphate

Composition changes with age, e.g: chondroitin decreases with age

29
Q

Formation and composition of the ECM of articular cartilage?

A

Synthesised, organised and degraded and maintained by chrondrocytes; usually, constitutes <2% of the total volume >98% is ECM

30
Q

Rate of ECM degradation compared to rate of replacement?

A

In normal joints, rate of degradation does not exceed rate of replacement In joint disease, rate of degradation exceeds rate of synthesis

31
Q

How is ECM degraded?

A

Using metalloproteinase proteolytic enzymes, e.g: collagenase and stromelysin

32
Q

How can the mechanical properties of cartilage be changed?

A

Change relative amounts of water, cartilage, proteoglycan

33
Q

Catabolic factors of cartilage matrix turnover?

A

Stimulate proteolytic enzymes and inhibit proteoglycan synthesis:

  • TNFα
  • IL-1
34
Q

Anabolic factors of cartilage matrix turnover?

A

Stimulate proteoglycan synthesis and counteract effect of IL-1:

  • TGF-β
  • Insulin-like growth factor (IGF-1)
35
Q

Markers of cartilage degradation?

A

Serum and synovial keratin sulphate, e.g: with age and in osteoarthritis

Type II collagen in synovial fluid - useful for evaluating cartilage erosion, e.g: osteoarthritis and rheumatoid arthritis

36
Q

Describe osteoarthritis

A

Cartilage and synovial composition and function deteriorate with age and repeated wear and tear

37
Q

Describe rheumatoid arthritis

A

Synovial cell proliferation and inflammation

38
Q

Describe gouty arthritis

A

Deposition of salt crystals of uric acid

39
Q

Describe pseudogout

A

Deposition of rhomboid shaped calcium pyrophosphate crystals

40
Q

Describe soft tissue rheumatism

A

Injury and inflammation to peri-articular structures, e.g. injury to the tendon causes tendonitis

41
Q

Radiological appearance of osteoarthritis?

A

Subchrondral sclerosis

Subchondral cyst

Early osteocyte formation

…these may be seen

Year 2 Physiology (21 decks)

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