Tissue Mechanics IV

Question 1

transmits tensile forces created in muscle to the bone

Answer 1

tendon

Question 2

what are tendons synthesized by?

Answer 2

tenocytes and tenoblasts

Question 3

limits joint motion

Answer 3

ligament

Question 4

which has more elastin?

Answer 4

ligament

both tendons and ligaments are mostly made of collagen

Question 5

tendon –>

Answer 5

fasicle
fibril
subfibril
microfibril
tropo-collagen

Question 6

the type I collagen fibril in the tendon are oriented …

Answer 6

in a general sense along one axis

Question 7

withstand unidirecitonal loads

Answer 7

tendonsligaments resist tensile stress in one direction and smaller stresses in other directions

Question 8

synovial sheaths around tendons do what biomechanically?

Answer 8

under the annular puleys that act as a fulcrum, adding a mechanic advantage to flexion

Question 9

those tendons that do not have synovial sheath may have…

Answer 9

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

Question 10

located under the paratenon and surrounds the tendon

Answer 10

epitenon

- fibrillar network of collagen

Question 11

epitenon fibers at 60 degrees to the tendon axis reorient to _______ after stretching

Answer 11

30 degrees

angle decreases

Question 12

thin network of crisscross collagen fibrils that envelop the primary, secondary and tertiary fiber bundles together

Answer 12

endotenon allow fiber bundles to glide with respect to each other

Question 13

carry blood vesels, nerves and lymph to tendon

Answer 13

endotenon

Question 14

disappears when stretched and reappears when unloaded

Answer 14

crimping of tendons

Question 15

biomechanical characteristics of tendons

Answer 15

• 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

Question 16

what are the disadvantages if tendon elasticity increases?

Answer 16

not as good for transmission of forces

Question 17

the greater cross sectional area of tendon, the ____________ stiffness and stress

Answer 17

greater the stiffness and greater the maximum stress STRAIN remains the same

Question 18

longer tendon length, the _________ stiffness and elongation

Answer 18

• the less the stiffness

- the greater the elongation

Question 19

secondary biomechanical functions of tendons

Answer 19

• eliminates unnecessary length of muscle (enables belly to be at distance from joint)
• absorbs shocks (limits damage to muscle)

Question 20

why do tendons have a toe region on stress-strain graph? (1.5-4%)

Answer 20

• waviness of fiber bundles straightened out

- continued elongation will result in increased stiffness

Question 21

tensile strength of tendon is ________ the strength of muscle it is attached to

Answer 21

twice

Question 22

describe creep and load in tendon

Answer 22

creep - isotonic 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)

Question 23

what happens to a tendon with repeated loads?

Answer 23

steady state develops after 10-20 cycles

- if not warmed up, the same amount of load causes more stress

Question 24

tendon is under risk of damage when …

Answer 24

• tension applied quickly
• tension applied obliquely
• tendon is preloaded before injurious load

Question 25

where will a ligament fail with high loading rate? low loading rate?

Answer 25

high- mid substance

low - bony insertion

Question 26

the physical properties of tendon and ligament tissue depend on …

Answer 26

number and quality of cross-links within and between the collagen molecules

Question 27

aging effects on biomechanical properties of tendons and ligament

Answer 27

up to 20 yo

• increased cross links
• decreased toe region
• increased collagen diameter
• increased tensile strength

after 20 yo

• decreased collagen diameter
• decreased stiffness and tensile strength

Question 28

gender differences

Answer 28

• tendon siffness and young’s modulus are lower in women

Question 29

immobilization causes …

Answer 29

weaker tissue, less stiff that undergoes larger elongation for the same load