10: Soft Tissue Mechanics IV - Vardaxis Flashcards
transmits tensile forces created in muscle to the bone
tendon
what are tendons synthesized by?
tenocytes and tenoblasts
limits joint motion
ligament
which has more elastin?
ligament
both tendons and ligaments are mostly made of collagen
tendon –>
fasicle fibril subfibril microfibril tropo-collagen
the type I collagen fibril in the tendon are oriented …
in a general sense along one axis
withstand unidirecitonal loads
tendons
ligaments resist tensile stress in one direction and smaller stresses in other directions
synovial sheaths around tendons do what biomechanically?
under the annular puleys that act as a fulcrum, adding a mechanic advantage to flexion
those tendons that do not have synovial sheath may have…
paratenon to reduce friction
- composed of loose fibrillar tissue (type I and III collagen)
- functions as an elastic sleeve that permits free movement of tendon against surrounding tissue
located under the paratenon and surrounds the tendon
epitenon
- fibrilalr network of collagen
epitenon fibers at 60 degrees to the tendon axis reorient to _______ after stretching
30 degrees
angle decreases
thin network of crisscross collagen fibrils that envelop the primary, seconday and tertiary fiber bundles together
endotenon
allow fiber bundles to glide with repect to each other
carry blood vesels, nerves and lymph to tendon
endotenon
disappears when stretched and reappears when unloaded
crimping of tendons
biomechanical characteristics of tendons
- tensile strength: due to collagen
- adequate flexibility: elastin fibers
- inextensibility: efficient transmission of force from muscles to bones
- inferior resistance against shear and compressive forces
what are the disadvantages if tendon elasticity increases?
not as good for transmission of forces
the greater cross sectional area of tendon, the ____________ stiffness and stress
greater the stiffness and greater the maximum stress
STRAIN remains the same
longer tendon length, the _________ stiffness and elongation
- the less the stiffness
- the greater the elongation
secondary biomechanical functions of tendons
- eliminates unnecessary length of muscle (enables belly to be at distance from joint)
- absorbs shocks (limits damage to muscle)
why do tendons have a toe region on stress-strain graph? (1.5-4%)
- waviness of fiber bundles straightened out
- continued elongation will result in increased stiffness
tensile strength of tendon is ________ the strength of muscle it is attached to
twice
describe creep and load in tendon
creep - isontonic contraction, tendon will lengthen slightly and more muscle fibers will be recruited in order to maintain the position of limb
stress - isometric contraction, stress in tendon decreases with time (night splint)
what happens to a tendon with repeated loads?
steady state develops after 10-20 cycles
- if not warmed up, the same amount of load causes more stress
tendon is under risk of damage when …
- tension applied quickly
- tension applied obliquely
- tendon is preloaded before injurious load
where will a ligament fail with high loading rate? low loading rate?
high- midsubstance
low - bony insertion
the physical properties of tendon and ligament tissue depend on …
number and quality of cross-links within and between the collagen molecules
aging effects on biomechanical properties of tendons and ligament
up to 20 yo
- increase cross links
- decrease toe region
- increase collagen diameter
- increase tensile strength
after 20 yo
- decrease collagen diameter
- decrease stiffness and tensile strength
gender differences
- tendon siffness and young’s modulus are lower in women
immobilization causes …
weaker tissue, less stiff that undergoes larger elongation for the same load
