Tissue Mechanics: Ligament/Tendon

Question 1

What is responsible for transmitting tensile forces?

Answer 1

tendon

Question 2

what is responsible for limiting joint motion?

Answer 2

ligament

Question 3

what is the difference in composition between tendon and ligament?

Answer 3

tendon has less elastin and less proteoglycans- so it will be less stretchy and attract less water

Question 4

describe the organization of collagen fibrils in tendons.

Answer 4

collagenous fibers are parallel to each other and interconnected –> makes them very strong

Question 5

Where are tendon synovial sheaths commonly found?

Answer 5

in the tendons of hands and feet

*is a closed duct around tendons gliding on bone surfaces

Question 6

synovial sheaths have two layers- inner (visceral) and outer (parietal) sheets. which layer has the synovial cells?

Answer 6

outer (parietal) sheet

Question 7

what is a paratenon?

Answer 7

those tendons that do not have a synovial sheath (Ex. achilles tendon) may have a paratenon to reduce friction

Question 8

which sheet in a paretnon has synovial cells?

Answer 8

inner surface

Question 9

what is an epitenon?

Answer 9

located under the paratenon and surrounds the tendon

Question 10

describe the organization of collagen fibers in the epitenon.

Answer 10

fibers are NOT parallel to each other; the strands run obliquely, longitudinal, or transverse to the long axis of the tendon

Question 11

after stretching, what happens to the angle of epitenon fibers at the tenon axis?

Answer 11

angle decreases (from 60 to 30 degrees)

Question 12

what is endotenon?

Answer 12

envelopes the primary, secondary, and tertiary fiber bundles together; allows fiber bundles to glide with respect to each other

Question 13

which tendinous structure carries blood flow, nerves, and lymph to the tendon?

Answer 13

endotenon

Question 14

what is the crimping of tendons due to?

Answer 14

cross-linking of proteoglycans

Question 15

what is the tensile strength of tendons due to?

Answer 15

collagen

Question 16

are tendons extensible or inextensible?

Answer 16

inextensible- tendons provide efficient transmission from muscle to bone (that is, they are NOT very elastic)

Question 17

do tendons have resistance against shear and compressive forces?

Answer 17

not really

Question 18

what are the disadvantages if tendon elasticity increases (reduced stiffness)?

Answer 18

a muscle will have to exert a greater force in order to move a bone the same distance as more stretch will be induced in the tendon before movement occurs

Question 19

what is the effect of increasing cross-sectional area on stress vs. strain curve for tendons?

Answer 19

the greater the cross-sectional area:

• the greater the stiffness
• the greater the max. stress
• but the SAME STRAIN

Question 20

at what percentage of strain does the tendon enter failure region?

Answer 20

4% or more

Question 21

what is the effect of creep on tendons?

Answer 21

in an isotonic contraction, the tendon will lengthen slightly and more muscle fibers will be recruited in order to maintain the position of the limb

Question 22

what is teh effect of stress-relaxation on tendons?

Answer 22

in an isometric contraction, the stress in teh tendon will decrease with time

Question 23

what is teh effect of increasing rate of load onto a tendon?

Answer 23

the faster you load a tendon, the more stress and stiff the tendon becomes

Question 24

what is the order in which the muscuolotendinous unit will disrupt?

Answer 24

1. myotendinous junction
2. osteotendinous junction
3. muscle belly
4. tendon

Question 25

when is tendon at risk of rupture?

Answer 25

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

Question 26

at a high loading rate, where will the point of failure be in a ligament?

Answer 26

mid-subtance area (at the tendon)

Question 27

at a low loading rate, where will the point of failure be in a ligament?

Answer 27

bony insertion

Question 28

up to 20 y/o, what properties are seen in tendons/ligaments?- in terms of # of crosslinks, toe region, collagen diameter, and tensile strength?

Answer 28

• increased cross-links
• decrease in toe region
• increased collagen diameter (collagen density)
• increased tensile strength during maturation

Question 29

what happens to properties of tendons/ligaments after 20y/o?

Answer 29

• decreased collagen diameter

- decreased stiffness and tensile strength

Question 30

how does YOung’s modulus for tendons compare in men vs. women?

Answer 30

tendon stiffness and Young’s modulus are LOWER in women than men

Question 31

what happens to tendons/ligaments after a period of immobilization?

Answer 31

results in weaker tissue, less stiff that undergoes larger elongation for the same load (can get reinjured easily)