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ANAT2012 > Bone L1: Biomechanics of Bone > Flashcards

Bone L1: Biomechanics of Bone Flashcards

1
Q

What graph is used for structural properties?

A

Load deformation graph

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2
Q

What graph is used for material properties?

A

Stress-strain graph

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3
Q

Why would a stress-strain graph be used?

A
  • Can use graph to compare to other materials
    • Ultimate stress can be compared to every other stress/strain graph
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4
Q

How does is tensile stress measured in stress-strain graph?

A

Can measure area = tensile stress

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5
Q

What is stress in a stress-strain graph?

A
  • Length
  • How much it stretches
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6
Q

What is the toe-region?

A
  • where crimp is being removed, becoming less wavy.
  • elastic (linear) region – slope = E (Pa), where material behaves elastically
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7
Q

What is modulus of elasticity?

A

stress/strain = E (Pa)

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8
Q

What is the yield point?

A

where permanent damage and non-linear behaviour starts

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9
Q

What is the plastic region?

A

post yield point, ductile behaviour with damage

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10
Q

What is the ultimate stress (strength)?

A

maximum stress (Pa) able to be supported

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11
Q

What is the ultimate strain?

A

maximum deformation/original length

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12
Q

What is the toughness?

A

area under curve, ‘resistance to failure’

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13
Q

What is the difference between a force-deformation curve and a stress-strain curve?

A

Basically – the units and terminology. Stress-strain curves are of more use due to the incorporation of ‘size’ of the thing under test. Normalised. This allows for comparisons with other materials in a meaningful way.

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14
Q

Structural VS material properties of bones

A
  • Bone material itself = weaker material = starts to bend –> adaptive response –> produce more bone larger bone (but poor quality)
  • Whole bone = good structure = relatively good strength
  • It is the structure of bone that makes it strong, not the material itself
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15
Q

What is bone fatigue?

A
  • Fatigue: continuous loading
  • decreased modulus
  • Once bone starts moving away from origin, permanent damage
  • Keep bending bone –> microcrystal –> damage permanent damage –> eventually failure
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16
Q

Bone is _____ rate dependent

A

Strain

  • More brittle but stronger –> increased rates of loading
  • More ductile rates of loading
17
Q

What is shear stress?

A

• More hallow (while same amount of bone) = more resistance to failure

18
Q

What torsion stress?

A

Torsion stress = Tr/J r = moment arm T = torque

  • Bone distributed further way = hollow= J = better
  • Bone not distributed as far away = J = risk of fracture
19
Q

What are the 2 inorganic components in bone matrix? What forces can be withstood?

A
  • 65% of hydroapatite
  • 99% of calcium
    • Bone brittleness and compressive strength
20
Q

What is the organic component in bone matrix? What forces can be withstood?

A
  • 33% of collagen
    • Bone tensile properties
21
Q

What forces can the inorganic components withstand?

A

Compressive force

22
Q

What force can the organic componnent withstand?

A

Tensile force

23
Q

What are some components of dense, lamellar or cortical bone?

A
  • Stiffness
  • Increased modulus = decreased toughness
    • High value of E
    • Small plastic region
    • High strength and density
24
Q

What are some components of spongy, trabecular or cancellous bone?

A
  • Toughness
  • Decreased modulus = increased toughness
    • Low value of E
    • Larger plastic region
    • Longer stress before failure
      • Low strength and density
25
Q

How is bone matrix maintained?

A

Bone cells account for 2% of bone, the rest is matrix Oestoblast Oestocytes Oestoclast

26
Q

What are oestoblasts?

A

Creates bone matrix

27
Q

What are oestocytes?

A

Maintains bone matrix

28
Q

What are oestoclasts?

A

• Breakdown of bone matrix • Larger than blasts

29
Q

What is microstructure of bone?

A

• Microstructure is very variable, complex but influences mechanical properties • Secondary osteons formed as replacement bone with primary bone

30
Q

Bone apposition and bone resorption: Osteoclasts

A

Nucleated stated

31
Q

Bone apposition and bone resorption: Osteocytes

A

Lacune

32
Q

Bone apposition and bone resorption: Resorbing surface

A

Active at this surface

33
Q

Bone apposition and bone resorption: Resting line

A

Bone growth stops –> restart again

34
Q

Bone apposition and bone resorption: Reversal line

A

Bone has been formed and eaten away and starts to build again

35
Q

What is parathyroid?

A

Chief cells = polypeptide hormone enhances Ca2+ release from bone PTH indirectly stimulates osteoclast activity

36
Q

What is calcitonin?

A

C-cells= linear polypeptide hormone inhibits Ca2+ absorption in intestines, renal tubular cells resorption and osteoclast activity Anti-osteoporosis effect

ANAT2012 (31 decks)

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