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Biomechanics > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What are the 4 primary tissue components

A

Collagen
Elastin
Ground substance
Water

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2
Q

What’s special about collagen

A

Continuous metabolic turnover through growth and maturity.

At maturity the fibers become MORE STABLE

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3
Q

Collagen is made by?

A

Fibroblasts

They are aligned in the extracellular matrix in a parallel arrangement

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4
Q

What can collagen do?

A

Stretch 110%

Increases ligaments size and strength

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5
Q

What does degeneration in ligaments result in?

A

Decrease in

Diameter
Density
Number
Mass
Metabolism
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6
Q

How far can elastin stretch?

A

150% from original length without breaking

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7
Q

What is ground substance

A

Aka Cement Substances

Water consists of 60-70% of total connective tissue content

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8
Q

What are the 4 main GAGs

A

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

Glucosamine is found in high concentration within GAGs *

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9
Q

What is the function of water in collagen

A

It acts as a powerful lubricant

Also helps maintain a CRITICAL DISTANCE between collagen fibers

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10
Q

What is tissue biomechanics

A

The development, maintenance, and re molding of tissue as well as the development of damage and disease

Ability to react to external forces

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11
Q

What are the types of mechanical forces acting on tissue

A 
Compression
Tension
Shear
Torsion
Bending
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12
Q

What is compression

A

When a load produces forces that push the material together

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13
Q

What is tension

A

When a structure is stretched longitudinally

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14
Q

What is shear

A

Forces acting parallel to each other in opposite directions

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15
Q

What is torsion

A

Forces twisting/rotating in opposite directions about the long axis

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16
Q

What is bending

A

Combination of tensile and compressive loads

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17
Q

Compression is almost constantly acting on what……….

A

The vertebral body and the inter vertebral disc

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18
Q

What are compression injuries

A

Bruises
Crushing injuries
Compression fractures
Pinching

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19
Q

Tension occurs during what kind of movements

A

Rotational

The annular fibers tend to bear the tensile loads

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20
Q

What are examples of tension injuries

A

Sprain/strain injuries
Avulsion fractures
Nerve traction injuries

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21
Q

What type of bone are most at risk for fracture from shear forces

A

Cancellous bones

Ex. Femoral condyles and tibial plateaus

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22
Q

What resist the shear forces in the spine?

A

The facet joints and the annulus fibrosis

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23
Q

What are examples of shear injuries

A

Brain injuries
Tibiofemoral translation such as ACL and PCL
Blisters
Spine injuries

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24
Q

What elements of the spine resist torsion and fail

A

Facets
Pars interarticularis
Capsular tears
Tears in the annulus

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25
Q

Spiral fractures of long bones are an example of ___________________

A

Torsional load failure

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26
Q

What are the most common responses to mechanical loading of tissues

A

Deformation
Growth and remolding
Failure

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27
Q

Deformation is when the object may translate or rotate unless in static equilibrium when results in local shape change

True or false

A

TRUE

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28
Q

What does the extent of deformation depend on

A

Material properties
Size and shape of object
Environmental factors
Forces

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29
Q

What is stress

A

The external force trying to deform the material

Measure the intensity of the force

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30
Q

What is strain

A

Magnitude of deformation from applied stress

Measure of the degree of deformation

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31
Q

Stress is what is ______ to an object while strain is _______ the object responds

A

Done, how

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32
Q

In addition to strain in direction of the applied stress there is also strain in an _______________ direction of loading

A

Orthogonal

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33
Q

What are three other qualities of tissues

A

Strength
Ductility
Toughness

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34
Q

What is strength

A

The maximum stress a tissue can withstand without permanent deformation

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35
Q

What is yield strength

A

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

36
Q

What is ultimate strength

A

The maximal stress that a material can withstand prior to the intimidation of failure

37
Q

What is failure strength

A

The stress at which the material actually breaks or ruptures

38
Q

What is ductility

A

Force per unit of area required to deform a material, REPRESENTED BY THE STEEPNESS OF THE STRESS/STRAIN CURVE

39
Q

____________ tissues fail at low stress but can withstand large strain

A

Ductile

40
Q

_____________ tissues can withstand high stress but fail with relatively low strain

A

Brittle

41
Q

What is toughness

A

The total energy required to cause a material to failure

Can be estimated by observing the TOTAL AREA under the stress/strain curve

42
Q

Bone is

A

More brittle, very strong. Overall toughness is low

43
Q

Tendons are

A

Moderate for both strength and ductility. Overall toughness is HIGH

44
Q

Ligament is

A

More pliant, lower strength. Overall toughness MODERATE

45
Q

Elasticity is….

A

Ability to return to the original shape when the load is removed

46
Q

What is yield point

A

Point at which the applied stress can lead to permanent deformation

47
Q

What is the plastic region?

A

The nonlinear response of material after the yield point- some degree of deformation will persist after removal of the stress

48
Q

What is viscosity

A

Property of materials to resist load that produce shear or tensile forces

Viscous (plastic) stretch= is putty like behavior

49
Q

Viscoelasticity will show what 3 time dependent loading characteristics

A

Creep
Relaxation
Hysteresis

50
Q

What is creep

A

Continued deformation over time when constantly loaded

51
Q

Relaxation is……

A

Eventual decrease in stress that will occur as fluid is no longer exuded

52
Q

Hysteresis is………..

A

Energy loss exhibited by viscoelastic materials when they are subjected to loading and unloading cycles

53
Q

What is micro-failure

A

Still elastic in this region, small amount of damage to the tissue

Grade one sprain

54
Q

Yield stress is

A

The stress when plastic deformation starts

55
Q

What is macrofailure

A

The tissue undergoes plastic deformation= grade 2 sprain

Ruptures result in a= grade 3 sprain

56
Q

What is anisotropic

A

Exhibits distinct mechanical properties when loaded along various axes because its structure differs in the transverse and longitudinal directions

57
Q

Cortical bone can withstand the most stresses in what order?

A

Compression>tension>shear

Also can tolerate longitudinal loads > transverse loads

58
Q

Cartilage is __________ tissue

A

Nonvascular

Composed of collagen, chondrocytes and ground substance

59
Q

Articular cartilage is ________ and subject to _______ and _______

A

Viscoelastic

Creep, relaxation

60
Q

Interfacial wear of articular cartilage is caused by

A

Adhesion and abrasion

61
Q

Fatigue wear of articular cartilage occurs due to

A

Repetition of high loads over a relatively short period of time or with repetition of low loads over an extended period of time

62
Q

Articular cartilage has only a __________ capacity for repair and regeneration

A

Limited

63
Q

The magnitude of the stress sustained by the articular cartilage is determined by the _____________ and the ________

A

Total load, how the load is distributed over the articular surface contact area

64
Q

Any intense stress concentration in the contact area will play a primary role in ___________________

A

Tissue degeneration

65
Q

How many discs in the adult body

A

23 discs

66
Q

How are the discs named?

A

Given a numeric name based on the segment ABOVE

67
Q

What percent of the vertebral column height is attributed to discs?

A

20-33%

68
Q

What are the three parts of a intervertebral disc

A

Nucleus pulposus

Annulus fibrosus

Cartilaginous end plates

69
Q

A greater ratio of disc to vertebral body ratio means

A

Greater spinal segmental mobility

70
Q

Where is the greatest disc to vertebral body height ratio in the spine

A

CERVICAL (2:5)

Lumbar (1:3)

Thoracic (1:5)= is the least ratio

71
Q

What makes up 70-90% of the Nucleus Pulposus

A

Water

90% at birth

80% at age 20

70% at old age

72
Q

Lumbar nuclei fill ____________ of total disc area. They are located more ________ than central

A

30-50%, posterior

73
Q

Cervical annulus is ____________ on the lateral borders and only ________________

A

Minimal, a thin strip in back

74
Q

How is the tissue arrranged in the annulus fibrosus

A

Concentric laminated bands, same direction within a band

HOWEVER, opposite directions in any two ADJACENT bands

75
Q

The annulus fibrosus is concentric laminated bands which appear to _________ one another obliquely, forming an angle of ______

A

Cross, 30 degrees

76
Q

Annular fibers are firmly attached to what?

A

Cartilaginous endplates via SHARPEYS FIBERS

77
Q

What structure narrows from the cervicals to lumbars in the spine?

A

Posterior Longitudinal Ligament

78
Q

WHat is the weakest area of the annulus?

A

POSEROLATERAL ASPECT

SAID IT WAS GONNA BE A TQ

Most likely spot for disc herniation in the lumbar spine

79
Q

What supplies the nucleus pulposus with most of its nutrition?

A

The end plate

80
Q

The outer portion of the end plate is ______________

A

Impermeable

81
Q

Diffusion of nutrients in the end plate occurs in the

A

Central portion

82
Q

True or false

Blood vessels go directly to the disc?

A

FALSE!

83
Q

Where do the annular fibers in the disc get their blood supply from?

A

Adjacent soft tissues

84
Q

The nucleus pulposus receives its blood supply from

A

Vertebral bodies

85
Q

The intervertebral disc represents a

A

Avascular and aneural tissue

86
Q

The disc undergoes

A

Rapid degernation and has limited self repair

87
Q

As disc degeneration and osteoarthritis become worse the disc becomes more

A

Innervated by sensory nerve fibers

Biomechanics (4 decks)

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