MSK L5 Bone and Cartilage

Question 1

Matrix: Made up of

Answer 1

Inorganic/mineral

Organic

Question 2

Matrix: Inorganic/mineral made up of

Answer 2

Hydroxyapatite

Question 3

Matrix: Inorganic/mineral Function

Answer 3

Compression strength

→ without = bendy

Question 4

Matrix:Organic made up of

Answer 4

Collagen and proteoglycans

→ without =brittle bones (osteogenesis impracta

Question 5

Matrix: Organic part function

Answer 5

Flexible strength

Question 6

Bones types:

Answer 6

1. Cortical or compact – more dense

2. Cancellous (trabecular or spongy) – less dense – bars and plates interconnected

Question 7

Matrix

Answer 7

Made up of many osteons

Question 8

Osteon

Answer 8

Concentric layers of lamellae around central blood vessels.

Question 9

Haversian canal

Answer 9

Contains blood vessels

Question 10

Interstial lamellae

Answer 10

In between two osteon

Question 11

Circumferential lamellae

Answer 11

Near matrix at surface

Question 12

Canaliculi

Answer 12

Radiate from lacunae from mature bones and osteocytes into the haversian canal. Channels provide passageway through compact bone to provide nutrition to the cells.

Question 13

Volkmann’s canal

Answer 13

Perforating blood vessels – allows them to join in outer membrane

Question 14

Osteoblast

Answer 14

Forming bone (multinucleated)

Question 15

Canaliculus

Answer 15

Radiate from lacunar of mature bone cell (osteocyte) into adjacent cavities with blood vessels to obtain nutrients.

Question 16

2 types of bone development (ossification):

Answer 16

1. Intramembranous → ossification of membrane to bone

2. Endochondral ossification→ calcification of cartilage model into bone

Question 17

Bone Growth:

Answer 17

Apposition growth
Process (width)
Endochonral growth (length) process

Question 18

Apposition growth

Process (width)

Answer 18

1. OB in periosteum secrete matrix and become trapped as osteocytes
2. Osteoclasts in crease diameter of medullary cavity
3. Increases diameter of bones until skeletal maturity

Question 19

Endochonral growth (length) process

Answer 19

1. Requires interstitial growth from cartilage first
2. Occurs at epiphyseal growth plates
3. Stops when growth plates ossify

Question 20

New bone laid down

Answer 20

Woven bone (random collagen)

Question 21

Remodelled why

Answer 21

More orderly collagen fibres

Question 22

Remodelling process

Answer 22

Osteoblasts lay down bone
Osteoclasts resorbed (remove) bone
→ Lamellar bone (ordered formed)

Question 23

Mature bone

Answer 23

Old bone is constantly being replaced by new bone

Bone shape changes in response to changing stresses

Question 24

Factors influencing bone growth and remodelling:

Answer 24

1. Mechanical factors
2. Genes
3. Hormones
4. Aging
5. Diseases

Question 25

Mechanical → influencing bone growth and remodelling:

Answer 25

Wolf’s Law → More stress increases osteoblasts activity → more bone → Less stress decreases osteoblast activity → less bone

Question 26

Genes: influencing bone growth and remodelling:

Answer 26

1. Determine potential shape and size 2. Height and bone mass is multifactorial (many genes involved and other factors) 3. Genes influence a. Growth hormone release b. Hormone receptor on bone cells c. Ability to absorb nutrients from the gut 4. Some genetic disorders influence bone growth e.g. dwarfism (FGFr3 mutation), turners syndrome

Question 27

Hormones: influencing bone growth and remodelling:

Answer 27

1. Growth, sex and thyroid hormones influence cell differentiation and metabolism 2. Overactive pituitary gland →excess GH

Question 28

Ageing: influencing bone growth and remodelling:

Answer 28

1. Osteoblast matrix production slows in comparison to osteoclast matrix resorption 2. Decreased collagen deposition results in more brittle bone (less flexible strength) 3. Bone mass peaks at 25-30 years then falls.

Question 29

Diseases: influencing bone growth and remodelling:

Answer 29

1. Osteoporosis → bone mass is reduced particularly in women after menopause (reduced oestrogen production). 2. Other factors affecting oestrogen levels a. Removal of ovaries b. Extreme exercise c. Anorexia nervosa d. Smoking 3. Cancellous bone is most affect as it is severly weakened if connections lost.

Question 30

FGFr3 →

Answer 30

normal proliferation of chondrocytes | Defective = poor proliferation of chondrocytes an abnormal growth of long bones in limb.

Question 31

Cartilage: types

Answer 31

1. Fibrocartilage – strongest and most rigid a. E.g. minicus 2. Hyaline cartilage a. Joint surface b. Epiphyseal growth plate 3. Elastic cartilage → balance between structure and flexibility a. E.g. ear b. Eustacian tube

Question 32

Cartilage growth

Answer 32

1. Appositional growth | 2. Interstial growth

Question 33

Perichondrium: Outer layer

Answer 33

Dense irregular CT with fibroblasts

Question 34

Perichondrium: Inner layer

Answer 34

Fewer fibres with chondroblasts

Question 35

Perichondrium: Appositional growth

Answer 35

Chondroblasts

Question 36

Perichondrium: Interstial growth

Answer 36

Chondrocytes

Question 37

Articular Cartilage: Type of

Answer 37

Hyaline cartilage

Question 38

Articular Cartilage: Found

Answer 38

On articular surfaces of bones

Question 39

Articular Cartilage:Has no

Answer 39

Perichondrium- as it forms part of the joint.

Question 40

Articular Cartilage: Growth

Answer 40

Similar to growth plate (but never ossifies) | Columns of cells → calcified cartilage and then form bone

Question 41

Articular Cartilage: Collagen structure

Answer 41

Arcades – high concentration of collagen on the surface.

Question 42

Articular Cartilage: Arcades

Answer 42

Type II collagen fibrils anchor proteoglycan matrix to bone

Question 43

Articular Cartilage: Growth stops

Answer 43

At a similar time to growth plate but never ossifies

Question 44

Function of Articular cartilage: Smooth

Answer 44

1. Reduces friction (heat → protein damage) | 2. Low-wear surface

Question 45

Function of Articular cartilage: Deformable and elastic

Answer 45

Distributes load evenly • Increased surface area → reduced force (peak contact stress) • Creep (deformation and load) also increase surface area during sustained loading

Question 46

Function of Articular cartilage: Visually

Answer 46

* Simple, inert tissue * Has high stiffness to compression and resilience * Exceptional ability to distribute load and great durability

Question 47

Function of Articular cartilage: Adult articular cartilage

Answer 47

Hypocellular Aneural Avascular

Question 48

Cartilage matrix

Answer 48

``` . Large number of proteoglycans attaching to hyaluronic acid chain → help to maintain the reversible deformity property of cartilage. → Maintains water within the structure 3. Collagen type II (mainly) a. Provide stable structure 4. Collagen (other types) ```

Question 49

Matrix Synthesis Promotion

Answer 49

TGF | IGF

Question 50

Matrix Synthesis Inhibition

Answer 50

IL-1 | TNF

Question 51

Matrix degradation Promotion

Answer 51

IL-1 | TNF

Question 52

Matrix degradation Inhibition

Answer 52

TGF | IGF

Question 53

Factors influencing cartilage metabolism

Answer 53

1. Mechanical factors 2. Injury 3. Aging 4. Diseases

Question 54

Mechanical → adaptive remodelling

Answer 54

Cartilage is poor at this ➢ High strain = deposition ➢ Low strain = resorption 1. Anabolic and catabolic processes adjusted to adapt matrix to mechanical demands. 2. Low below 1 MPa may be catabolic while load above 1 MPa may be a anabolic stimulus.

Question 55

Injury and repair:

Answer 55

1. Lack capillaries within cartilage. 2. Nutrients from diffusion (synovium not bone). 3. Chondrocytes do not normally divide in adult but still secrete matrix (repairs normal wear). 4. Tears/lesions never fully heal.

Question 56

Ageing:

Answer 56

1. Decreased PG and collagen turnover a. Collagen disruption b. PGs lost c. Water lost on compression d. Tissue damage 2. Increase no-enzymatic glycation NEG) 3. Impaired joint lubrication a. Friction/heat b. Fibrillation c. Osteoarthritis

Question 57

Non-enzymatic glycation:

Answer 57

1. Cross-linking between collagen and sugars 2. Process not controlled by enzymes or cells 3. Advanced glycatino end=products (AGEs) make tissue stiffer, more brittle and yellowish (seen with ageing)