Bone Mechanics, Repair, and Tissue Engineering Flashcards
bone is inherently a _____ tissue
trabecular bone acts as a damper; can bear mechanical forces and distribute them _____; if you overload your bone and you experience a crack, this mechanism makes it not as devastating
osteoporosis: bone resorbing cells become _____; spit out acid and decalcify bone and no activation of osteoblasts; preferential resorption in _____ over cortical > cells are sitting on surface, and trabecular bone has higher _____ than cortical, thereby there is more resorption in this area
mechanical evenly over-active trabecular SA
Stress and Strain
elongation of rod: relationship bt _____ and how much _____ it gets
epsilon is essentially a _____ (unitless)
stress = _____ / _____ (force is normalized via the cross sectional area)
_____ relationship bt stress and strain, and related by E (elastic modulus, tells you how _____ the material is)
force longer percent change force cross sectional area linear
Rule of Mixtures
“_____ Model”
-Lower bound for composite modulus
“_____ Model”
-Upper bound for composite modulus
Reuss
Voigt
Intrinsic vs. Extrinsic Properties
load displacement curve (_____ relationship initially)
linearity holds true until the object is no longer _____ (returns to original with zero loss, no loss of energy); no longer returns to original shape
once bent too much, plastic deformation = permanent deformation
_____ (the peak) tells you how much force can be applied before it breaks
slope tells you linear/elastic _____
I parameter > tells you how big the _____ of the rod is; small I, stress _____
linear elastic ultimate load stiffness outside increase
Mechanical Regulation of Tissue Differentiation
osteoblasts in fractures can lay approx. _____ of bone per day
direct bone formation, _____ fromation (left picture, cast, etc.)
stabilize the bone so that it can bend, everytime the animal takes a step, the two fragments get closer together > _____; when you have interfragmentary strain (motion bt fragments) > you have _____ bone formation, and then you have cartilage that forms a callus > and then the cartilage gets replaced by bone; this method is a much faster way to heal bone
_____ stabilizes the fracture, which then can become remodeled
if you have a fracture (particularly true in children) > if bones are not straight, the bone will _____ itself out and heal by itself > occurs via endochondral process; callus formation, muscles begin to pull to align the fragments
the endochondral process is _____; depends on mechanical environment to determine how the cells behave
1mm
intramembranous
cyclic loading
endochondral
callus
straighen
mechanosensitive
Tissue Differentiation
the mechanical environment determines what type of _____ it will become
if stem cell gets little mechanical stimulus > you’ll end up with _____
more compressive stresses, you get _____
if mostly shape change > mostly _____, fibrous tissue
tissue
bone
cartilage
fibrocartilage
Fracture repair: recapitulating development
_____ and _____ have similar structure
callus
GP
Biomaterials: Design Parameters
- _____ (natural/synthetic)
- _____
- _____
- _____ properties
- _____ (connectivity, porosity, scale)
material biocompatibility degradation mechanical structure
Natural Biomaterials
hyxdroxyapatite scaffold > slurry of hydroxyapatite (calcium phosphate)
sugars derived from seaweed (_____) > biocompatible, degradable, can modify it (chemical modifications), can crosslink it
collagen > triple helix of polypeptides
alginate
Engineered hydrogels
reduce the doses of the proteins that you’re examining
GF > BMP2 > put it on a sponge and stick it in a defect > bone formation; however, BMP diffuses out and bone formation occurs in _____ locations
(used in cervical vertebrae, but would choke people due to bone formation surrounding the neck)
_____ allow the GF to remain within the complex, and only the cells that are targeted will sense it
HA based matrices, can link different peptides to them; allows cells to grab onto matrix, but also fools the cell into thinking its next to another cell > make cells think t hey’re in totally different _____
ectopic
hydrogels
environments
Biologics
- Growth factors
- DNA/RNA
- CRISPR
_____ > editing genomes
Cas9 identifies the _____ domain of DNA, in conjunction with CRISPR you can program where cuts are made in DNA
in DMD mice, this complex restored complete _____ of muscle when targetting specific genetic sequences
CRISPR
repeating
function
Considerations: kinetics & dose
deliver GF on different matrices (i.e. hydrogels, do not want on collagen sponge)
can use _____ doses and put on alginate sponge (traps BMP in matrix); only way you used to be able to fix was by _____ the dose with the collagen sponge, but it would _____
higher
lower
leak
A tale of twins
made use of the fingerprint to tell the twins apart; fingerprints are not regulated by the _____
fingerprints arise because of differential _____ rates between the epidermis and dermis, that causes a buckling of the _____
the patterns that form while it undergoes a buckling process (_____), are influenced by the _____ that are put on that finger during the _____ process
genome
proliferation
dermis
mechanical
forces
developmental
Mechanical cues in endochondral ossification
_____ forces are important in long bone development
mechanical forces are critical for _____ ossification process
developmental problem in babies, if there’s not sufficient _____, the womb constricts around the baby and the baby cannot kick > the hips don’t form correct (developmental hip _____, caused by a lack of amniotic fluid) > it’s becasu of the biochemical environment that is defective that amniotic fluid provides
mechanical
endochondral
amniotic fluid
dysplasias
Bone defects & mechanical loading
_____ plate: contralateral control
_____ plate: axial loading
stiff
compliant
