Lecture 3 - Tissue Mechanics: Bone & Cartilage

Question 1

What two principle structure components are found in bone?

Answer 1

collagen and hydroxyapatite

Question 2

What is collagen?

Answer 2

organic material found in all the body’s connective tissues

Question 3

What is the % of bone organic content does collagen make up?

Answer 3

90%

Question 4

What is the % of bone dry weight does collagen make up?

Answer 4

40%

Question 5

What type of collagen is found in bones?

Answer 5

type I collagen

Question 6

What are hydroxyapatites?

Answer 6

calcium phosphate-based mineral found primarily between the collagen fibers

Question 7

What is the % of bone dry weight does hydroxyapatite make up?

Answer 7

60%

Question 8

How can hydroxyapatites be found?

Answer 8

in crystal form as a mineral

Question 9

What is bone growth?

Answer 9

from immature to mature bone

Question 10

What is woven bone?

Answer 10

immature bone with cartilage fibers randomly distributed to give some strength in all directions

Question 11

What do osteoclasts do?

Answer 11

dig tunnels into the bones as it matures

Question 12

What do osteoblasts do?

Answer 12

dig tunnels with type I collagen

Question 13

What do osteocytes do?

Answer 13

mineralize collagen with hydroxyapatites

Question 14

What are osteons?

Answer 14

the hollow canals which represent the structural units of bone

Question 15

What is the biomechanics of bones determined by?

Answer 15

gravity, PA, hormones, age

Question 16

Functions of bones

Answer 16

1. protect internal organs
2. support body weight
3. provide rigid kinetic links and muscle attachment sites
4. facilitates muscle action
5. storage for minerals
6. manufactures blood cells

Question 17

What are the 2 kinds of bones?

Answer 17

cortical and cancellous

Question 18

What kind of bone is cortical bone?

Answer 18

dense bone (compact)

Question 19

Where are cortical bones found?

Answer 19

in the mid shaft of the femur

Question 20

What % of skeletal mass does cortical bone comprise?

Answer 20

80%

Question 21

What % of bone surface does cortical bone comprise?

Answer 21

33%

Question 22

What kind of bone is cancellous bone?

Answer 22

spongy or trabecular

Question 23

What % of skeletal mass does cancellous bone comprise?

Answer 23

20%

Question 24

What % of bone surface does cancellous bone comprise?

Answer 24

67%

Question 25

Where are cancellous bones found?

Answer 25

in the interior of the femoral head

Question 26

What is Wolff's Law?

Answer 26

form = function

Question 27

What does an applied bending moment in bones create?

Answer 27

compression and tension

Question 28

What are the loading modes of bones?

Answer 28

tension, compression, torsion, shear, bending

Question 29

What are cortical bones' response to strain?

Answer 29

2%

Question 30

What are cancellous bones' response to strain?

Answer 30

7%

Question 31

How are bones classified?

Answer 31

anisotropic

Question 32

What does anisotropic mean?

Answer 32

different mechanical properties in different directions

Question 33

Which bone is stronger and stiffer for more strenuous activities?

Answer 33

cortical bones

Question 34

What happens at very high strain rates?

Answer 34

ultimate strain decreases and cortical bone exhibits a ductile (due to viscous properties)

Question 35

What do changes in mechanical properties of bone depend on?

Answer 35

age and activity

Question 36

Are are the 5 steps of fracture healing?

Answer 36

1. inflammatory response 2. repairs cells gather at fracture site 3. in 2 weeks, a callus begins to form 4. callus calcifies and becomes woven bone 5. woven bone undergoes remodelin

Question 37

When does callus strength increase?

Answer 37

as bone mineral density increase

Question 38

What are the 3 kinds of cartilage?

Answer 38

articular cartilage, fibrocartilage, elastic cartilage

Question 39

Where is articular cartilage found?

Answer 39

in synovial joints to permit motion between bony segments

Question 40

Examples of articular cartilage

Answer 40

hip, knee, elbow

Question 41

What is fibrocartilage?

Answer 41

inflexible and tough, considerable tensile and compressive strength

Question 42

Examples of fibrocartilage

Answer 42

annulus fibrosis of the intervertebral disc, meniscus

Question 43

What is the function of elastic cartilage?

Answer 43

helps to maintain the shape of structures

Question 44

Examples of elastic cartilage

Answer 44

ear, trachea

Question 45

Does cartilage have a blood supply?

Answer 45

no

Question 46

How are joints enclosed?

Answer 46

in a fibrous tissue capsule

Question 47

What is the fibrous tissue capsule lined with?

Answer 47

the synovial membrane that secretes synovial fluid

Question 48

What does articular cartilage in synovial joints provide?

Answer 48

a bearing surface to reduce friction and wear by helping to distribute loads between opposing bones

Question 49

What is cartilage mostly made of?

Answer 49

water (70-85%)

Question 50

What is the remainder of cartilage mostly made of?

Answer 50

proteoglycans, collagen, lipids

Question 51

What makes the electrical charge of the proteoglycan spread out?

Answer 51

the electrical charge

Question 52

What is the spread of proteoglycans limited by?

Answer 52

the collagen framework, contributing to the compressive stiffness

Question 53

What happens when the collagen framework is damaged?

Answer 53

the compressive stiffness decreases

Question 54

What is the mechanical response of cartilage linked to?

Answer 54

the flow of fluid through the tissue

Question 55

What is viscoelasticity?

Answer 55

time dependant behaviour due to a fluid-like component

Question 56

What is anisotropic?

Answer 56

different properties in different directions

Question 57

As the water content in cartilage increases...

Answer 57

cartilage becomes less stiff and more permeable

Question 58

How does mechanical failure of cartilage happen?

Answer 58

by shear stress more than tensile