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Semester 2 FS Exam 2 > Bone > Flashcards

Bone Flashcards

1
Q

Two major components of bone

A

Organic

Inorganic

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2
Q

Collagen

A

90% organic matrix
Provides tensile strength to bone
Type I

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3
Q

Proteoglycans

A

Composed of glycosaminoglycan complexes
Inhibit mineralization
Numerous functions ranging from growth factors to binding properties
Partially responsible for compressive strength of bone

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4
Q

Osteocalcin

A

Produced by osteoblasts, related to regulation of bone density, most abundant non collagen matrix protein

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5
Q

Osteonectin

A

Secreted by platelets and osteoblasts, organization of mineral within matrix

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6
Q

Osteopontin

A

Cell binding protein

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7
Q

Inorganic matrix

A 
60% dry weight
Almost entirely Ca Hydroxyapatite
Provides compressibe strength of bone
Responsible for mineralization of bone
Primer mineralization occurs in holes and pores
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8
Q

Microstructure - 7 levels

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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9
Q

Bone Strcutre

A 
Coritcol = 5-30% porous
Cancellous = 30-90% porous, no osteons
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10
Q

Osteon formation - bone growth

A
  1. Osteoblasts secrete bone matrix
  2. Groove with BV is a tunnel
  3. Periosteum lining tunnel becomes endosteum - secrete bone matrix
  4. Osteoblasts form new lamellae - new osteon is created
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11
Q

Cortical bone types

A

lamellar

woven

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12
Q

Lamellar bone type

A

cortical bone type
Parallel layers of lamellae
Mineralized collagen fibers are parallel within each lamella, direction of fibers may alternate btw adjactent lamalla

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13
Q

Woven bone type

A 
Corticol bone type
Quickly formed
Poorly organized, fibers are more or less randomly arranged
More minrralized than lamellar
Weaker than minteralized
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14
Q

Cortical Compact bone

A 
80% skeleton
Osteons connected by haversion canals
Nutrition via interosseous
Slow tunrover - remodeling
High stiffness (youngs modulus)
High resistance to torsion and bending than cancellous
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15
Q

Woven bone

A

Immature of pathologic
Collagen is arranged irregularly
Isotropic - mechanical properties ind of orientation so stress applied

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16
Q

Woven bone exists in

A 
Fetal skeleton
Fx callus
Tooth sockets
Bone forming tumors
Stages of accelerated bone formation
17
Q

Trabecular bone

A

Formed by organization of plate and rod like struts called trabeculae
Trabeculae are about 200 um thick

18
Q

Cancellous/Trabecular bone - spongy

A 
Less dense
More remodeling along lines of stress (wolfe)
Much larger SA
Higher turnover
Lower apaprent modulus (less stiff)
More elastic
More resistant to compressive forces
19
Q

Wolffs law

A

Bone remodels in response to the stresses applied to it
Possibel that remodeling occurs to keep strain (not stess) btw certain upper and lower limits
If strain is too high - bone is laid down along lines of stress to make thicker and denser
If strain is too low - bone is lost making bone less dense - Osteoporosis

20
Q

Bone growth/.formation

A

Customize the shape of bones during ggrowth in accordance with mechanical needs

21
Q

Metaphyseal modeling

A

Reduces bone diamter during growth

22
Q

Diaphyseal modeling

A

Increase bone diameter

  • addition of bone to periosteum
  • resorption of bone at endosteum
23
Q

Bone stress/strain

A

Bone has nonlinear elastic behavior

Moderate plastic region

24
Q

Bone mechanical characteristics vary according to

A 
geometry 
load mode applied
Direction of load
rate of loading
Frequency of loading
25
Q

Cortical bone graph

A

Can tolerate higher tensile forces in both long and trans directions
Bone is more compliant in the transverse direction with compression and tensile
Boen responds better to comp stresses whether long or trans

26
Q 
Stress strain relationship
Cortical vs cancellous 
Load
Deformation
Energy stored
A

cortical bone is stiffer
Load = Cortical > cancellous
Deformation = Cancellous > cortical
Energy stored = Canellous > cortical

27
Q

Bone - ansiotropic

A

Bone exhibits diff mechanical properties when loaded along diff axes

28
Q

Bending load - bone

A

Compression and tension

Stress not equaly distributed - inc magnitude farther from neutral axis

29
Q

Torsional load

A

Twist about an axis
Shear stress is developed
Mag of stress proportional to distance from axis

30
Q

Rate dependency

A 
Viscoelastic
Inc loading rate
Inc stiffness (as rate inc)
Inc load
Loading rate influences the fracture pattern and the soft tissue damage
31
Q

Reduced load effect on bone

A

Takes less erngery to deform a bone that has been at rest for a while
More compliant after immob

32
Q

Aging

A 
Decreased strain
Decreased energy storage
Peak = 40-50 yo
Energy to fail dec with age (toughness)
Strain dec
Tissue density stays the same
Apparent density (amount of bone) is dec

Semester 2 FS Exam 2 (6 decks)

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