Tissue mechanics Flashcards
(18 cards)
Apects of tissue failure mechanics
- Magnitude
- Repetition
- Duration (Creep)
- Intervals bw load cycles
- Biological meterial
- direction of load
how does repitition affect injury
Over time tissue tollerance will continue to diminish untill eventually somethiong u could always do hurts u
What is Creep
a slow elongation of tissue due to being loaded at a constant force
difference is you load something quick then slow
if you load something quick in the body, tollerance will momentarially go up because water doesnt have time to leave the system ( thus manipulation better than mobalization)
Typical stress/ strain curve
- elastic region
- Yield point- point where the material starts to break but doesnt completely break (nonelastic region)
- Failure point- the point at which the material breaks
Collagen vs elastin stress strain curve
- stiff, has steep slope, can withstand force w/o stretching
- Can be stretched but will hit a wall and have a steep slope after
easiest to break a bone w
shear force
Wolffs law
bone will adapt and become stronger in the direction u load it
in boot top fracture which side will break first
tension side
failure mechanism in stress fracture and what inturupts it
tiny scratch will happen in the bone and if more force is applied stress begins to build arround the crack\
-haversion cannals and lacunea inturupt the growth
How does trabeculae bone survive compression
Trabeculae will bend sideways under compression but sty strong due to horzintal cross ties
–if compression is >10% strain we get plastic deformation
Collagen direction in skin, ligs and tendon
skin- haphazard pattern to handle forces from all dif firections
ligs- cross ties to also withstand joint play
Tendon- 100% collagen all orientated one direction
Ligaments- what happens at low and high loading rates
low- avulsions likely
high- tear likely
what increase in strength do you get w fascia attached
10%
Why does streching increase the stiffness of fascia
after streching, water is drawn into the tissue which temporarily increases stiffness and matrix hydration
In girls ACL laxity and injury is associated with which parts of their period
laxity- luteal
injury- follicular
3 degrees of msucle strain
1- few muscle fibres tear, minor swelling + discomfort
2- greater damage to muscle and clear loss of function
3- cross sectional tear of muscle, complete loss of function
3 phases of muscle injury
Destruction- necrosis of myofibres, formation of scar bridge, inflammation
Repair- Phagocytosis of necosis, regeneration of myofibres and capilarization
Remodeling- Maturation of regenerated myofibres, reorganization of scar tissue, recovery of muscle
