Tissue Mechanics: Bone Flashcards
what are the 2 major components of bone?
organic matrix- 40%
inorganic matrix- 60%
what are the constitutents of the organic matrix of bone?
type 1 collagen
proteoglycans
non-collagenous matrix proteins
amorphous ground substance
what are the constitutents of the inorganic matrix of bone?
calcium hydroxyapatite
what provides tensile strength to bone?
type 1 collagen
what is the significance of cross-linking of collagen fibers?
cross-linking decreases solubility and increases the tensile strength
what inhibits mineralization of bone?
proteoglycans
what are proteoglycans composed of?
glycosaminoglycans
what is the function of proteoglycans?
partially responsible for COMPRESSIVE strength of bone (but must of it comes from the inorganic matrix instead)
give some examples of the non-collagenous matrix proteins.
osteocalcin
osteonectin
osteopontin
which matrix protein is most abundant and responsible for regulating bone density?
osteocalcin
what provides compressive strength of bone?
(inorganic matrix): calcium hydroxyapaptite
what is responsible for the mineralization of bone?
inorganic matrix- calcium hydroxyapatite
describe the structure of cortical vs. cancellous bone. which is more porous? which is stratified into osteons?
cortical bone- less porous; is stratified into layers of osteons
cancellous bone- more porous; no osteons
what are the types of cortical bone?
lamellar bone & woven bone
describe lamellar bone vs. woven bone, which is more dense? which is stronger? describe fiber arrangement
lamellar bone- fibers are parallel within each lamella; less dense but it stronger than woven bone
woven bone- fibers are randomly arranged; more dense but not as strong as lamellar bone
describe some characteristics of compact bone (cortical)- in terms of turnover, Young’s modulus, and resistance to torsion/bending.
- slow turnover
- relatively high Young’s modulus (stiff)
- higher resistance to torsion and bending than cancellous
describe some characteristics of cancellous (trabecular) bone- in terms of turnover, YOung’s modulus, resistance, density.
- less dense; more remodeling along lines of stress
- much larger surface area
- higher turnover
- lower apparent modulus (more elastic)
- more resistance to compressive forces
what is Wolff’s law?
bone remodels in response to the stresses applied to it ; this remodeling occurs to keep strain (not stress) between certain limits
- if strain is too high –> bones become thicker and denser
- if strain is too low -> bones become less dense and may lead to osteoporosis
what is metaphyseal modeling?
(reduces bone diameter during growth) by resorption of bone at the metaphysis and adding it to the ends of bones
what is diaphyseal modeling?
(increases bone diameter)- addition of bone on the periosteum and resorption of bone at endosteum
describe the stress-strain curve for bone.
bone has a non-linear elastic behavior with a moderate plastic region.
bone mechanical characteristics vary according to:
- geometry
- load mode applied
- direction of load
- rate of loading
- frequency of loading
Compare cortical and cancellous bone for load:
cortical >cancellous
Compare cortical and cancellous bone for deformation:
cancellous > cortical (easier for cancellous bone to be deformed)
compare energy stored between cortical and cancellous bone.
cancellous bone> cortical
what is the peak age range for Young’s modulus?
40-50 y/o
what is the peak age for ultimate stress?
40-50 y/o
how does energy to fail change with age?
energy to fail decreases
how does strain change with age?
strain decreases
how does tissue density change with age?
stays the same
how does apparent density change with age?
amount of bone decreased
