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Tissue Biomechanics > Cartilage > Flashcards

Flashcards in Cartilage Deck (40)
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1
Q

The nose and ear are made up of what kind of cartilage?

A

Elastic cartilage

2
Q

What structures are composed of fibrocartilage?

A

1 - iliac surface of SI joint
2 - menisci of the knee
3 - annular fibers of the disc

3
Q

Function of joint cartilage (2)

A

1 - decrease contact stress by spreading load over a larger area
2 - allow movement of articular surfaces with minimal wear and friction

4
Q

Can hyaline cartilage heal quickly? Why or why not?

A

No, because there is no nerve supply, no blood supply, no lymph supply.

5
Q

What are the components of cartilage?

A

Solid matrix
Chondrocytes
Water

6
Q

The solid matrix of cartilage is composed of what?

A

60% collagen and 40% proteoglycan gel

Percentages are by weight

7
Q

Function of collagen (2)

A

1 - provides ultrastructure for cartilage
2 - provides tensile stiffness and strength

Note: cartilage undergoes compression; collagen resists tensile load — collagen helps cartilage do its job by resisting tensile load

8
Q

Why is collagen better suited (compared to cartilage) in resisting tensile loads rather than compressive?

A

?

Loading of tensile force makes the fibers straighten.

9
Q

How is collagen arranged in zone 1?

A

Superficial zone: thickest zone. Random packed, random orientation in planes parallel to the surface

10
Q

How is collagen arranged in zone 2?

A

Middle zone — least amount of thickness. Random orientation and loosely packed.

11
Q

How is collagen arranged in zone 3?

A

Deep zone — medium amount of thickness. Perpendicular ordination, anchor to bone and fibrocartilage.

12
Q

The proteoglycan gel is composed of (2)

A

1 - Protein core

2 - Aggrecans

13
Q

What are aggrecans composed of and how do they help establish sponge model?

A

Aggrecans are negatively charged so they repulse/resist each other. This makes an inherent stiffness. It’s the anions that stiffens the Proteoglycan Gel and resists compression.

14
Q

How does water move to protect joints?

A

1 - proteoglycan gel attracts cations and sets up osmotic pressure

2 - cations osmotically draw water molecules into cartilage

So the cartilage stiffens and swells due to A) the repulsive force of aggrecans and B) the osmotic pressure attracting water

Under stress:
A- water squeezed out
B- produces increased swelling pressure (osmotic pressure)
C- equilibrium is re-established when swelling pressures balances the stress

15
Q

What zone is most of the water located in the cartilage? and why is this important?

A

Superficial zone (zone 1).

That means 70% of the water is free to move

16
Q

Most of the creep in cartilage is due to what?

A

Exudation of fluid

17
Q

What is the speed of creep as it applies to cartilage? Under a constant load…

A

Viscoelastic material deforms quickly at first and then more slowly over time until equilibrium is met

18
Q

What is the syringe effect?

A

With a slow load, more fluid comes out

With a fast load, there is resistance of fluid movement.

19
Q

How does cartilage behave in high speed loading?

A

Little deformation.

Because, syringe effect: not enough time to squeeze water out of tissue, therefore cartilage is very stiff.

E.g. discs = good shock absorbers

20
Q

How fast is the restoration when you unload after a slow load?

A

1 - Immediate restoration to 90% via elastic recoil
2 - Slower restoration via swelling pressure

E.g. being on your feet all day: take a seat and you’ll restore 90% thickness nearly immediately

21
Q

What kind of fluid acts as lubricant between articular surfaces?

A

Synovial fluid

22
Q

Name 2 types of lubrication

A

Fluid film

Boundary

23
Q

What is fluid film lubrication?

A

Thick film of lubricant that separates surfaces and occurs in physiologic loading

24
Q

Types of fluid film lubrication (2)

A

Hydrodynamic

Squeeze film

25
Q

What kind of fluid film lubrication creates a lifting action that keeps surfaces apart and reduces friction?

A

Hydrodynamic lubrication

26
Q

What kind of fluid film lubrication happens on non-parallel surfaces and with tangential movement?

A

Hydrodynamic lubrication

27
Q

What kind of fluid film lubrication is sufficient for high loads for short durations?

A

Squeeze lubrication

28
Q

What kind of fluid film lubrication are perpendicular force? And the viscosity holds the lubricant together so that it doesn’t escape from between the surfaces.

A

Squeeze lubrication

29
Q

What kind of lubrication is good in “severe loading” and is when monolayer of synovial fluid absorbs to surfaces?

A

Boundary lubrication

30
Q

The unwanted removal of material from solid surfaces by mechanical action

A

Cartilaginous wear

2 types: interfacial wear and fatigue wear

31
Q

What kind of cartilage wear happens from interaction of articular surfaces and is unlikely in healthy cartilage because of effective lubrication?

A

Interfacial wear

32
Q

What are 5 qualities of Interfacial wear?

A
By adhesion and abrasion
Wear produces surfaces defects
Softening and increased permeability
Fluid leakage
Loss of lubrication (into defects in the surface)
34
Q

What kind of cartilage wear occurs with repetitive cyclic loading (and the reloading occurs before cartilage has time to fully re-imbibe)?

A

Fatigue wear

35
Q

What type of cartilage wear involves repetitive stress on matrix, collagen fiber disruption, proteoglycan macromolecule disruption and microstructural disruption that leads to degeneration?

A

Fatigue wear

Note: repetitive exudation and imbibition may “wash out” degraded proteoglycan gels

36
Q

What occupations lead to cartilage injury because of high repetitive loads?

A

Football player’s knees and ballet dancer’s ankles (high repetitive loads)

37
Q

Loss of muscle balance can led to cartilage injury because:

A

Loss of flexibility prevents loads from being evenly distributed through joint surface

38
Q

“Pebble in a shoe” defect focuses load into one area and can lead to cartilage injury. How might this happen (4)?

A

Intra-articular fracture
Meniscectomy
Slipped femoral epiphysis
Ligamentous instability

39
Q

Disease that can lead to cartilage injury though matrix destruction include:

A

RA
Joint space hemorrhage
Collagen disorders

40
Q

Immobility can lead to cartilage injury because of

A

Decreased synovial fluid circulation

41
Q

Rapid high impact loads may not allow fluid to redistribute rapidly enough, causing high internal fluid pressure at the PG-collagen matrix (what kind of cartilage wear is this?)

A

Fatigue wear