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Biomechanics V2 > 6: Tissue Mechanics II - Vardaxis > Flashcards

6: Tissue Mechanics II - Vardaxis Flashcards

1
Q

which is greater in bone: organic or inorganic matrix?

A

organic matrix 40% dw; inorganic matrix 60% dw

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2
Q

what is the major component of inorganic matrix?

A

calcium hydroxyapatite

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3
Q

total percentage water of bone

A

10%

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4
Q

collagen is _____ organic matrix

A

90%

- provides tensile strength to the bone

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5
Q

structure of collagen in bone

A
  • type I
  • triple helix -> fibril
  • hole zone b/w fibrils
  • pores b/w sides of parallel molecules
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6
Q

x-linking in bone collagen _____ solubility and _____ tensile strength

A
  • decreases

- increases

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7
Q

what are proteoglycans?

A

glycosaminoglycan complexes

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8
Q

proteoglycans __________ mineralization

A

inhibit

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9
Q

proteoglycans are partially responsible for ________ strength of bone

A

compressive

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10
Q

non-collagenous matrix prtns (osteocalcin/osteonectin/osteopontin) ________ mineralization and bone formation

A

promote

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11
Q

produced by osteoblasts, related to regulation of bone density, most abundant non-collagen matrix prtn

A
  • osteocalcin
  • other non-collagenous matrix prtns are osteonectin (secreted by patelets and osteoblasts, organization of mineral within matrix) and osteopontin (cell binding prtn)
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12
Q

inorganic matrix provides the _______ strenght of bones

A

compressive

- also responsible for mineralization of bone; primary mineralization occurs in holes and pores

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13
Q

seven hierarchical levels of bone

A
  1. isolated crystals and collagen fibrils
  2. mineralized collagen fibril
  3. mineralized fibril array
  4. fibril array patterns
  5. single osteon
  6. spongy and compact bone
  7. whole bone
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14
Q

cortical v. cancellous bone

A 
cortical = 5-30% porous
cancellous = 30-90% porous, no osteons
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15
Q

woven v. lamellar cortical bone

A

lamellar: parallel layers of lamellae; mineralized collagen fibers are parallel within each lamella; direction of fibers may alternate between adjacent lamellae
woven = quickly formed; poorly organized; more mineralized than lamellar; weaker than lamellar

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16
Q

which is weaker: lamellar or woven cortical bone?

A

woven

17
Q

compact cortical bone has a _______ resistance to torsion and bending than cancellous

A

higher

18
Q

describe compact/cortical boen

A
  • 80% of skeleton
  • osteons connected by haversian canals
  • cement line define outer border of osteon
  • slow turnover
  • high young’s modulus
19
Q

immature or pathologic bone

A

woven bone

the collagen is arranged irregularly

20
Q

where might you find woven bone?

A 
fetal skelton
fx callus
tooth sockets
bone forming tumors
stages of accelerated bone formation
21
Q

isotropic

A

mechanical properties independent of orientation of stresses applied

woven bone is isotropic

22
Q

trabecular bone aka

A

cancellous bone or spongy bone

23
Q

describe cancellous bone

A
  • less dense
  • more remodeling along lines of stress
  • LARGE surface area
  • high turnover
  • low apparent modulus
24
Q

which type of bone is more elastic?

A

cancellous bone

also more resistant to compressive forces

25
Q

wolff’s law and bone

A
  • bone remodels in response to the stresses applied to it

- remodeling occurs to keep strain (NOT STRESS) between certain limits

26
Q

if strain is too high, how does bone respond?

A

new bone is laid down along the lines of stress, and the bone becomes both thicker and denser

  • if strain too low, bone is lost, making the bone less dense, this inactivity may lead to osteoporosis
27
Q

_________ modeling to reduce bone diameter during growth; ______ modeling to increase bone diameter

A

metaphyseal;

diaphyseal

28
Q

describe diaphyseal modeling

A
  • addition of bone on the periosteum
  • resorption of bone at endosteum
  • diaphyseal modeling to increase bone diameter
  • diaphyseal modeling can alter curvature
29
Q

describe the stress-strain relationship of bone

A
  • nonlinear elastic behavior

- moderate plastic region

30
Q

________ is stiffer than ______ bone

A

cortical; cancellous

31
Q

deformation is greater in ________ bone

A

cancellous

32
Q

load is greater in ______ bone

A

cortical

33
Q

energy stored is greater in _______ bone

A
  • cancellous

- trabecular bone can absorb considerable energy while maintaining a minimum mass

34
Q

anisotropic behavior of bone

A

bone exhibits different mechanical properties when loaded along different axes

( longitudinal - stiffer more plasticity; transverese - less stiffness, no plasticity)

35
Q

magnitude of stress from torsional load is proportional to …

A

distance from axis

36
Q

increased loading rate = ____ stiffness and _______ load

A

increased both

37
Q

bed rest reduces bone mass by _____ when immobilized

A

1%/wk

38
Q

what part of the strain-stress relationship changes with aging?

A
  • decreased strain

- decreased energy storage

39
Q

aging variations in tibial trabecular bone

A
  • peak E 40-50 yo
  • peak ultimate stress 40-50 yo
  • energy to fail decreases with age
  • strain decreased
  • tissue density did not change
  • apparent density (amount of bone) decreased

Biomechanics V2 (12 decks)

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