Exam 1: Tissue Mechanics Flashcards

1
Q

Primary tissue components

A

Collagen
Elastin
Ground substance
Water

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2
Q

Collagen has continuous _____ through growth to maturity

A

Metabolic turnover

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3
Q

At maturity the collagen fibers become more

A

Stable

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4
Q

Collagen chains are synthesized ans secreted by

A

Fibroblasts

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5
Q

Collagen molecules align in the ____ in a ____ arrangement

A

Extracellular matrix; parallel

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6
Q

Collagen can stretch to ____ its original length

A

110%

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7
Q

Ligaments change under tension

A

Inc ligament strength

Inc ligament size

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8
Q

Increased lig size is accomplished by

A

Inc # of collagen fibrils
Inc collagen fibril diameter
Inc cross-linking
Inc collagen fibril packing density

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9
Q

Immobilization causes these degenerative ligament (collagen) changes

A
Dec diameter
Dec density
Dec fibril #
Dec overall mass
Dec metabolism
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10
Q

Immobilization at ligament-bone junction changes

A

Inc osteoclast activity
Bone resorption
Disruption of diffusion

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11
Q

Immobilization increases the risk of ____ at the ligament-bone junction

A

Avulsion injuries

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12
Q

Elastin can stretch to ____ its original length

A

150%

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13
Q

Age-related changes to elastin

A

Lose resiliency
Fragmentation/fraying
Calcification
Inc cross-links

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14
Q

Contents of Ground Substance

A

GAGs
Plasma proteins
Small proteins
Water

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15
Q

GAGs, plasma proteins and small proteins all attract

A

Water

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16
Q

Water = _____% of total CT content

A

60-70%

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17
Q

4 major GAGs

A

Hyaluronic acid
Chondroitin-4-sulfate
Chondroitin-6-sulfate
Dermatan sulfate

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18
Q

_____ is found in high concentration within GAGs

A

Glucosamine

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19
Q

Hyaluronic acid + water is a powerful _____

A

Lubricant

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20
Q

Water maintains _____ between collagen fibers which allows ____ and prevents _____

A

Critical distance

Allows free gliding; prevents excessive cross-linking

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21
Q

Mechanical forces play an important role in ______ of tissue as well as ______

A

Development, maintenance, remodeling

Damage and disease

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22
Q

Tissue biomechanics is study of how different parts of human body _____

A

React to external forces

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23
Q

When a load produces forces that push material together

A

Compression

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24
Q

When a structure is stretched longitudinally

A

Tension

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25
Q

Forces acting parallel to each other in opposite directions

A

Shear

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26
Q

Forces twisting/rotating in opposite directions about long axis

A

Torsion

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27
Q

Combination of tensile and compressive loads

A

Bending

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28
Q

Behavior of compressed structures depends on

A

Its length; how far or long load is applied

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29
Q

Nearly constant compressive forces are transmitted to

A

Vertebral body and IVD

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30
Q

Examples of compression injuries

A

Bruises
Crushing
Compression fractures
Pinching

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31
Q

Compression fractures happen a lot in _____ because there is _____

A

Older female patients

Too much force/too little bone density

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32
Q

Tension is a _____ force

A

Stretching or pulling

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33
Q

Tension elements of the body are ___

A

Soft tissues

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34
Q

Tensile forces occur in the IVD during ____ movements

A

Rotational

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35
Q

Examples of tension injuries

A

Sprain/strain
Avulsion fractures
Nerve traction injuries

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36
Q

_____ bones are most at risk for fracture due to shear forces

A

Cancellous

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37
Q

In the spine ____ resist shear forces

A

Facet joints and annulus fibrosus fibers

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38
Q

Examples of shear injuries

A

Brain injuries
ACL/PCL injuries
Blisters
Spine injuries

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39
Q

Excessive torsion can result in failure of:

A

Facet joint
Part interarticularis
Capsular tears
Circumferential tear of annulus

40
Q

____ fractures of long bones are another example of torsional load failure

A

Spiral

41
Q

_____ is a combination of compression and tension

A

Bending

42
Q

Tissue responses in response to force

A
  1. Deformation
  2. Growth/remodeling
  3. Failure
43
Q

Local shape change due to applied forces

A

Deformation

44
Q

Extent of deformation depends on

A
  1. Material properties
  2. Size/shape
  3. Environmental
  4. Force (magnitude, direction, duration)
45
Q

External force acting to deform a material

A

Stress

46
Q

Stress measures the ___ of the force

A

Intensity

47
Q

Magnitude of deformation as result of applied stress/loading

A

Strain

48
Q

Strain is a measure of _____

A

Degree of deformation

49
Q

Stress is _____, strain is _____

A

What is done to object; how object responds

50
Q

Strain is ____ to stress

A

Proportional

51
Q

In addition to strain in direction of applied stress, there is also strain ____ to direction of loading

A

Perpendicular (orthogonal)

52
Q

Maximum stress a tissue can withstand without permanent deformation

A

Strength

53
Q

Yield strength

A

Stress at yield point of a material beyond which permanent deformation will occur

54
Q

Ultimate strength

A

Maximal stress a material can withstand prior to initiation of failure

55
Q

Failure strength

A

Stress where material actually breaks/ruptures

56
Q

Ductility represents how much ____ the structure can sustain _____

A

Force and deformation; before it fails

57
Q

Ductile tissues fail at ____ but can withstand ____

A

Low stress; large strain

58
Q

Brittle tissues can withstand ___ but fail with ___

A

High stress; low strain

59
Q

Total energy required to cause material failure

A

Toughness

60
Q

Toughness is estimated by observing

A

Total area under stress/strain curve

61
Q

Bone = more ___, very ____

A

Brittle; strong

62
Q

Overall toughness of bone =

A

Low

63
Q

Tendon = moderate for both

A

Strength and ductility

64
Q

Overall toughness of tendon =

A

High

65
Q

Ligament = more ___ and lower ____

A

Pliant; strength

66
Q

Overall toughness of a ligament =

A

Moderate

67
Q

Ability to return to original shape when load is removed

A

Elasticity

68
Q

Plastic region

A

Response of material after yield point

Deformation persists after stress removal

69
Q

Elastic stretch represents _____ behavior

A

Spring-like

70
Q

Property of materials to resist loads that produce shear/tensile forces

A

Viscosity

71
Q

Viscous stretch refers to

A

Putty-like behavior

Deformation by tensile stress remains after stress is removed

72
Q

When material shows both properties of viscosity and elasticity

A

Viscoelasticity

73
Q

Viscoelasticity is affected by both ____ and ____ it is subjected to constant load

A

Rate of loading; length of time

74
Q

Viscoelastic structures show time dependent loading characteristics:

A

Creep
Relaxation
Hysteresis

75
Q

Continued deformation over time when constantly loaded

A

Creep

76
Q

Creep in tissue occurs due to

A

Expulsion of water

77
Q

Eventual decrease in stress that occurs as fluid is no longer exuded

A

Relaxation

78
Q

Energy loss by viscoelastic materials when subjected to loading/unloading

A

Hysteresis

79
Q

The larger the load the ___ the hysteresis

A

Greater

80
Q

What does it mean when hysteresis decreases

A

Less capacity to absorb the shock energy

81
Q

What can happen as a result of decreased hysteresis

A

Inc deformation

Molecular disruption

82
Q

Compliant tendons can absorb elastic energy more easily they have ___ hysteresis which could be related to ___ injury risk

A

Dec; dec

83
Q

In general, weight training will ____ stiffness, while flexibility exercises will ___ compliance

A

Increase; increase

84
Q

_____ hysteresis is advantageous

A

Low

85
Q

Hysteresis is dependent on

A

Rate of loading/unloading

86
Q

Dynamic activities (plyo/ballistics) can increase pliability of MTC and thereby

A

Dec hysteresis (dec injury risk)

87
Q

Toe region

A

Normal range of motion

88
Q

Toe region is the little force required to remove the

A

Crimping/slack in the tissue

89
Q

After toe region, tissue

A

Resists elongation much more strongly

90
Q

Micro-failure occurs after

A

Taking out slack in soft tissue

91
Q

During micro-failure the tissue is still _____

A

Elastic

92
Q

Example of micro-failure

A

Grade 1 sprain (small amount of damage)

93
Q

Yield stress is the stress when

A

Plastic deformation starts

94
Q

In yield stress, when the force is taken off

A

It will stay deformed

95
Q

Plastic deformation example

A

Grade 2 sprain

96
Q

Example of tissue rupture

A

Grade 3 sprain