Tissue Mechanics: Cartilage Flashcards
Where is articular (hyaline) cartilage found?
joints, growth plates
Where is fibrocartilage found?
IV disks, mandibular condyles, meniscus
Where is elastic cartilage found?
epiglottis, eustachian tube
does cartilage function as a shock absorber?
NO
what is teh function of cartilage?
- supports/transmits loads across mobile surfaces
- distributes joint loads over a wider area (stress reduction)
- stabilize and guide joint motion
- lines the ends of bones (prevents wear)
- lubrication reduces friction coefficient
describe the composition of hyaline cartilage
water (58-78%)
chondrocytes (1%)
proteoglycans
where is most of the water in cartilage found?
middle zone
describe the orientation fo cartilage in its different layers.
superficial layer: parallel
middle layer: oblique
deep zone: perpendicular
describe the proteoglycan content in cartialge
increases from surface till the middle zone and diminishes towards the deep zone
(so there is the most proteoglycan in the middle)
the proteoglycan + collagen network limits flow of water in/out of the tissue
true
what provides cartilage with its tensile strength?
type 2 collagen
tissues with high proteoglycan content exhibit what properties?
- high water content
- low hydraulic permeability
- highly resists compressive stress
- damage to proteoglycans will result in increased water mobility and impaired mechanical function
what happens to cartilage under tension?
-collagen fibers stretch along the axis of loading
what does tensile modulus (stiffness) depend on?
- type/amount of collagen cross-linking
- density of collagen fibers
- orientation of collagen fibers
- tensile modulus is FLOW INDEPENDENT
tensile modulus varies 5-25 MPa depending on what?
- location of joint surface
- depth of specimen
- orientation of specimen relative to joint surface
what happens to cartilage under compressive force?
permeability decreases
what is the response of cartilage to shear force?
stretching & deformation of the solid matrix. Deformation but
- no change in volume
- no pressure gradient
- no fluid flow thru the matrix
for a 2-4mm human or bovine articular cartilage, how long does it take to reach creep equilibrium?
4-16 hours
the higher the rate of loading results in what effect on cartilage?
more stress/more resistance
what effect does OA have on cartilage metabolism?
imbalance of cartilage metabolism (anabolism/catabolism is disrupted)
what effect does OA have on cartilage tensile and compressive stiffness?
both decrease
*fracture stress also decreases
what does decreased tensile and compressive stiffness manifest as histologically and microscopically?
disorganized ECM (disrupted collagen and GAG network)
what happens to hydraulic permeability with OA?
increases
what are some predisposing factors to OA?
Immobilization, joint instability, overuse, trauma, injury, or obesity