Bone

Question 1

2 Types of Macroscopic Bone

Answer 1

1. Cortical

2. Cancellous

Question 2

Structure of Cortical bone

Answer 2

Osteons/Haversian systems
1. Osteon - outer border = cement lines
2. Vascular canals = Haversian canals (long axis)
Volkmanns canals (TV)
3. Interstitial Lamellae

Question 3

Cortical bone charactertics (2)

Answer 3

Slow turnover rate

High Youngs modulus

Question 4

Cancellous bone characteristics

Answer 4

High turnover rate

Lower Youngs Modulus

Question 5

2 types of Microscopic bone

Answer 5

1. Woven Bone

2. Lamellar bone

Question 6

Lamellar vs Woven bone features

Answer 6

Lamellar = remodelled bone
Organised
Stress oriented
Stronger and less flexible;

Question 7

Osteoblasts origin

Answer 7

Undiff mesenchymal cells

Question 8

OB function

Answer 8

Form bone - produce non-mineralised matrix

Question 9

CK that stimulate OB formation (4)

Answer 9

BMP - Mesenchymal - osteoprogenitor cells

1. RUN x2
2. CBFA (core bind fac alpha)
3. PDGF
4. IDGF

Bump, run and core

Question 10

Periosteum layers (2)

Answer 10

1. Inner cambium layer

2. Outer fibrous layer

Question 11

OB features

Answer 11

1. Great synthetic ability

2. High ALP activity

Question 12

3 fates of OB

Answer 12

1. Inactive bone lining cells
2. Osteocytes
3. Apoptosis

Question 13

Osteocyte functions (3)

Answer 13

1. Control calcium
2. Phosphate metabolism
3. Respond to mechanical, electrical and chemical (PTH) stimuli

Question 14

OB receptors (2)

Answer 14

1. PTH

2. 1,25 dihydroxyvit D

Question 15

PTH effect on OB (2)

Answer 15

Stim production of RANKL

Jagged1- Notch immune response

Question 16

OC origin

Answer 16

Myeloid hamatopoieitic cells

Monocyte progenitor

Question 17

OC microscopic appearance

Answer 17

Multinucleated giant cells

Question 18

OC: Where does bone resorption occur

Answer 18

1. Ruffled border - Howship’s Lucunae

Question 19

How do OC attach to bone?

Answer 19

Integrins at sealing zone

avb3 –> vitronectin (on bone surface)

Question 20

How do OC absorb inorganic bone? (3)

Answer 20

LOW PH THROUGH:

1. Carbonic anhydrase system
2. ATP dependant proton pumps
3. Na/H+ exchange system

Question 21

How do OC absorb organic bone? (2)

Answer 21

PROTEOLYTIC ENZYMES

1. TRAP
2. Cathepsin K

Question 22

Components of Organic component (4)

Answer 22

1. Collagen I
2. Proteoglycans
3. Proteins (Osteocalcin, osteonectin, Osteopontin)
4. CK and GF ( IL1,6, IGF, TGF B BMPs)

Question 23

Proteoglycan function

Answer 23

Compressive strength

Question 24

Collagen structure

Answer 24

1 x a2 2xa1 (triple helix)

Question 25

Osteocalcin produced by?

Answer 25

Mature OB

Question 26

Osteocalcin functions (3)

Answer 26

1. Promotes mineralization 2. Attracts OC 3. Marker of bone turnover

Question 27

Osteonectin secreted by? @)

Answer 27

Plts + OBs

Question 28

Osteonectin Function?

Answer 28

Regulation of mineralization

Question 29

Osteopontin function?

Answer 29

Cell binding protein - anchors osteoclasts to matrix

Question 30

Inorganic bone components? (2)

Answer 30

``` Calcium hydroxyapatite Osteocalcium phosphate (Brushite) ```

Question 31

Blood supply to bone comes from 3 main sources

Answer 31

1. Nutrient artery 2. Metaphyseal-Epiphyseal system 3. Periosteal system

Question 32

Nutrient artery supplies what portion of mature bone>

Answer 32

inner 2/3 via Haversion system

Question 33

Met-epi system arises from what vascular plexus?

Answer 33

Periarticular (ie geniculate)

Question 34

Periosteal system capillaries enter at which sites?

Answer 34

Major muscle attachments

Question 35

Normal direction of blood flow in bone?

Answer 35

Centrifugal (in -> out)

Question 36

Type of blood flow after reaming + normal venous flow + immature bone?

Answer 36

Centripetal (out -> in)

Question 37

Major source of growth plate nutrition?

Answer 37

Perichondrial artery

Question 38

OB produce which substance to stimulate OC?

Answer 38

RANKL

Question 39

OB secretes which substance to inhibit OC>

Answer 39

Osteoprotegrin

Question 40

Osteoprotegrin function?

Answer 40

Binds to and sequesters RANKL

Question 41

Factors that inhibit OC (5)?

Answer 41

1. OPG 2. Calcitonin 3. Estrogen (decrease in RANKL) 4. TGF beta 5. IL 10 ``` Osteoclast Cant Eat The Iliac wing ```

Question 42

OC activation? (6)

Answer 42

1. RANKL 2. PTH 3. IL1 4. Vit D 5. IL6 (Myeloma) 6. MIP-1A (Myeloma)

Question 43

Bone mets mediated by which pathway?

Answer 43

RANK/RANKL