Physiology of bone repair

Question 1

Label the long bone components using the labels below:

periosteum
articular cartilage
compact bone
epiphyseal line
spongy bone
medullary cavity
endosteum

Answer 1

1 = articular cartilage
2 = spongy bone
3 = epiphyseal line
4 = periosteum
5 = compact bone
6 = medullary cavity
7 = endosteum

Question 2

There are 2 types of bone that make up the bone we know, which come under the category of lamella. The outer layer and the inner layer. What are these layers called?

Answer 2

• outer layer = compact bone

- inner layer = trabecular bone

Question 3

What is an osteon?

Answer 3

• rod like unit, with lots of them making up bones
• main structural component of compact bones
• contain circular lamella within and then a haversham canal in the middle

Question 4

Osteons are the main structural component of compact bones. There are 3 main cell types contained within osteons, what are they?

Answer 4

1 - osteoblasts
2 - osteoclasts
3 - osteocytes

Question 5

What is the basic function of osteoblasts, osteoclasts and osteocytes?

Answer 5

• osteoblasts = re-build bone
• osteoclasts = degrade bone
• osteocytes = nutrition and bone formation

Question 6

Lamella are a key component of bones, what are lamella?

1 - form of bone cell
2 - organised sheets of mineralised osteoid
3 - spaces containing osteocytes
4 - communication channels between osteocytes

Answer 6

2 - organised sheets of mineralised osteoid

Question 7

At the centre of the osteon is a canal that carries VAN (veins, arteries and nerves). What is this canal called?

1 - dystrophian canal
2 - Eusabian canal
3 - Volkmann canal
4 - Haversian canal

Answer 7

4 - Haversian canal

Question 8

Bones contain canaliculi, what are these?

1 - form of bone cell
2 - organised sheets of mineralised osteoid
3 - spaces containing osteocytes
4 - canals used for communication between osteocytes

Answer 8

4 - canals used for communication between osteocytes

Question 9

Lacunae are contained within osteons. What are lacunae?

1 - form of bone cell
2 - organised sheets of mineralised osteoid
3 - spaces containing osteocytes
4 - canals used for communication between osteocyte

Answer 9

3 - spaces containing osteocytes

- lacunae are connected by canaliculi

Question 10

Which location on the bone would you find the majority of trabecular bone?

1 - epiphysis
2 - diaphysis
3 - periosteum
4 - epiphyseal plate

Answer 10

1 - epiphysis

Question 11

Which location on the bone would you find the majority of compact bone?

1 - epiphysis
2 - diaphysis
3 - periosteum
4 - epiphyseal plate

Answer 11

2 - diaphysis

Question 12

There is a dense fibrous connective tissue lining the outside of the bone and the medullary cavity of the bones. What are these 2 layers called and where are they located?

1 - epimysium and endosteum
2 - perimysium and endosteum
3 - endosteum and periosteum
4 - periosteum and epimysium

Answer 12

3 - endosteum and periosteum

• outer layer of bone = periosteum
• medullary layer = endosteum

Question 13

What is bone homeostasis?

Answer 13

• balance between bone breakdown and bone re-absorption

Question 14

Osteoclasts are a cell in bones responsible for bone breakdown. What is the origin of this cell type?

1 - progenitor cell
2 - hematopoietic stem cell
3 - red blood cells
4 - immature osteocytes

Answer 14

2 - hematopoietic stem cell

- form from multiple monocytes

Question 15

Osteoblasts are a cell in bones responsible for building bone. What is the origin of this cell type?

1 - progenitor cell
2 - hematopoietic stem cell
3 - red blood cells
4 - immature osteocytes

Answer 15

1 - progenitor cell

- originate from mesenchymal cells

Question 16

What is the primary type of collagen that we can find in bone?

1 - type I
2 - type II
3 - type III
4 - type IV

Answer 16

1 - type I

Question 17

What are 3 main components that make up the inorganic matrix of bone that is mineralised, accounting for 70% of bone?

1 - Ca2+ + Cl- ions + Na+ ions
2 - Ca2+ + phosphate + hydroxyl ions
3 - Ca2+ + phosphate + K+ ions
4 - Ca2+ + phosphate + Cl- ions

Answer 17

2 - Ca2+ + phosphate + hydroxyl ions

Question 18

During bone formation, does bone begin as organic or inorganic?

Answer 18

• begins as organic

- undergoes calcification and then becomes inorganic

Question 19

The 3 main components that make up the inorganic matrix of bone that is mineralised, accounting for 70% of bone are Ca2+ + phosphate + hydroxyl ions. What is the name given to this structure?

1 = hydroperoxide
2 = hydroxyapatite
3 = calcium phosphate
4 = calcium hydroxylate

Answer 19

2 = hydroxyapatite

Question 20

Once osteoclasts break down bone, there is something contained within bones that become visible to osteoblasts that then facilitate bone growth and development. What is contained within the bone extracellular matrix that facilitates this bone growth?

1 - Ca2+
2 - growth factors
3 - growth factor inhibitors
4 - osteocytes

Answer 20

2 - growth factors

Question 21

Which type of bone cell when mature becomes trapped in bone extracellular matrix and becomes an osteocyte?

Answer 21

• osteoblasts

Question 22

Progenitor cells, which will go onto develop into osteoblasts are contained within bones. Where are they contained within the bones?

1 - endosteum
2 - periosteum
3 - periosteum + endosteum
4 - medullary cavity

Answer 22

3 - periosteum + endosteum

Question 23

Indian Hedgehog (IHH) is a growth factor involved in what?

Answer 23

• bone reformation

Question 24

The Wingless-related integration site (WNT) is a pathway that has been heavily kinked with the growth and development of what?

Answer 24

• bone growth and development

Question 25

Bone morphogenic proteins (BMP) are growth factors that have been heavily kinked with the growth and development of what?

Answer 25

- bones

Question 26

Fibroblasts growth factors are growth factors that are heavily involved in the growth and development of what inorganic structure?

Answer 26

- bone

Question 27

There are 4 main stages of bone remodelling. Label the image below using these labels: reabsorption formation reversal quiescence

Answer 27

``` 1 = reabsorption 2 = reversal 3 = formation 4 = quiescence ```

Question 28

The 1st stage of bone formation is reabsorption. What is is this stage? 1 - osteoclasts degrade bone, Ca2+ and P released into blood 2 - osteoclast degrade bone, Ca2+ and phosphate remain in bones 3 - osteoclasts degrade bone, Ca2+ and P released into blood 3 - osteoblasts degrade bone, Ca2+ and P released into blood

Answer 28

1 - osteoclasts degrade bone, Ca2+ and P released into blood

Question 29

The 2nd stage of bone formation is reversal. What is is this stage? 1 - degraded extracellular matrix is recycled to rebuild bone 2 - degraded extracellular matrix is used as energy by osteoblasts 3 - degraded extracellular matrix by osteocytes is removed by macrophage 4 - degraded extracellular matrix by osteoclasts is removed by macrophage

Answer 29

4 - degraded extracellular matrix by osteoclasts is removed by macrophage

Question 30

The 3rd stage of bone formation is formation. What is is this stage? 1 - growth factors activate osteoblasts and new bone formation begins 2 - growth factors activate osteocytes and new bone formation begins 3 - growth factors inhibit osteoclasts and macrophages 4 - growth factors stimulate osteocytes to stimulate osteoblasts

Answer 30

1 - growth factors activate osteoblasts and new bone formation begins - osteocytes are formed when osteoblasts get trapped in bone matrix

Question 31

Once new bone has been formed, what is the final stage of bone remodelling? 1 - recycling phase 2 - remodelling phase 2 3 - quiescent stage 4 - bone re-formation stage

Answer 31

3 - quiescent stage

Question 32

We distinguish between new and old bone as new bone contains what? 1 - cement line 2 - osteocytes 3 - osteoclasts 4 - macrophages

Answer 32

1 - cement line | - cement line is where new bone has been deposited but high in collagen as not that mineralised yet

Question 33

What cell type in bones act as a mechanoreceptors that are able to detect that bones are undergoing mechanical force and therefore need to strengthen? 1 - macrophages 2 - osteocytes 3 - osteoclasts 4 - osteoblasts

Answer 33

2 - osteocytes

Question 34

When a bone is fractures, what is the first thing that happens inside the bone to begin the bone repair process? 1 - ischaemia 2 - osteoblast activation 3 - release of growth factors 4 - haematoma

Answer 34

4 - haematoma | - bleeding outside of blood vessels into bones following by inflammation with macrophages

Question 35

Once the bone is fractured and haematoma, bleeding outside of blood vessels into bones following by inflammation with macrophages has occurred there will be the formation of the first type of tissue. This is the first stage of recovery following tissue damage. What is this tissue called? 1 - quiescence 2 - granulation 3 - reversal 4 - bone reformation

Answer 35

2 - granulation | - fibrin and fibroblasts migrate to the area and are deposited

Question 36

With any tissue damage there will also be tissue debris. What cell type will migrate to the area and remove the damaged tissue? 1 - T cells 2 - macrophages 3 - platelets 4 - dendrites

Answer 36

2 - macrophages

Question 37

What is osteoid and osteon?

Answer 37

- osteoid = unmineralised bone tissue (collagen, fibrous tissue, polysaccharides etc...) - osteon = mineralised bone (rod like structures that make up the main structural component of bone)

Question 38

During weeks 2-3 following a bone fracture osteoblasts will be activated by growth factors released from the extracellular matrix of the bone. What will osteoblasts begin to deposit at the ends of the broken tissue? 1 - lacunas 2 - phosphate 3 - osteoid seam 4 - Ca2+

Answer 38

3 - osteoid seam | - mainly collagen acting like a scaffold for Ca2+ and phosphate to be deposited

Question 39

During weeks 2-3 following a bone fracture osteoblasts will be activated by growth factors released from the extracellular matrix of the bone. Osteoblasts begin to deposit osteoid seam (collagen like scaffold for new bone) at the ends of the broken tissue, forming what? 1 - articular cartilage 2 - macrophages 3 - soft callus 4 - osteocytes

Answer 39

3 - soft callus | - formed of woven bone and hyaline cartilage

Question 40

During weeks 2-3 following a bone fracture osteoblasts will be activated by growth factors released from the extracellular matrix of the bone. Osteoblasts begin to deposit osteoid seam at the ends of the broken tissue called soft callus. Between 4-16 weeks, this soft callus then becomes what? 1 - articular cartilage 2 - macrophages 3 - hard callus 4 - osteocytes

Answer 40

3 - hard callus

Question 41

During bone repair, is the bone initially laid down compact or trabecular?

Answer 41

- trabecular | - eventually replaced by compact bone

Question 42

What is 1,25-Dihydroxyvitamin D?

Answer 42

- molecular active form of vitamin D

Question 43

What affect does parathyroid hormone have on bones?

Answer 43

- binds to osteoblasts and that then releases RANK-L and Macrophage-Colony Stimulating Factor (M-CSF) - M-CSF and RANK-L stimulate macrophages then form multi nucleated osteoclasts - osteoclast degrade bone and release Ca2+ and phosphate into blood

Question 44

What affect does the active form of vitamin D have on bones?

Answer 44

- binds to vitamin D receptors on osteoblasts - osteoblasts then secrete M-CSF and RANK-L - M-CSF and RANK-L stimulate macrophage pre-cursors to form multi-nucleated osteoclasts - osteoclasts degrade bone releasing Ca2+ and phosphate

Question 45

What affect does parathyroid hormone have on the kidneys?

Answer 45

- binds to proximal convoluted tubules - inhibits re-absorption of phosphate - binds to principle cells and increases Ca2+ reabsorption

Question 46

What affect does parathyroid hormone have on the vitamin D levels?

Answer 46

- converts inactive vitamin D into its active form

Question 47

What affect does vitamin D have on the GIT?

Answer 47

- enters enterocytes | - increased Ca2+ and phosphate absorption from food

Question 48

Which hormone is produced by the C cells of the thyroid and is important for regulating Ca2 levels? 1 - calcitonin 2 - parathyroid hormone 3 - thyroid hormone 4 - inactive vitamin D

Answer 48

1 - calcitonin

Question 49

Calcitonin is a hormone is produced by the C cells of thyroid and is important for regulating Ca2 levels. How does this hormone regulate Ca2+ levels?

Answer 49

- binds and inhibits osteoclasts, inhibiting bone breakdown

Question 50

Once parathyroid hormone bind with osteoblasts they initiate the release of macrophage-colony stimulating factor (M-CSF) and RANK-L, which stimulate the maturation of osteoclasts that initiate bone degradation. What cytokine does PTH inhibit the release of from osteoblasts, that would inhibit osteoclasts? 1 - osteoprotegerin 2 - calcitonin 3 - osteoid seam 4 - IL-2

Answer 50

1 - osteoprotegerin | - osteoprotegerin is normally released from osteoblasts when osteocytes have finished doing their jobs

Question 51

Once PTH has bound to osteoblasts and they have released cytokines RANK-L and M-CSF. What do these 2 cytokines then do?

Answer 51

- stimulate pre-osteoclasts forming mature osteoclasts

Question 52

Osteoclasts contains lysosomes and a ruffled surface, what is important about these 2 features? 1 - ensure immune cells cannot phagocytose them 2 - ensure bone degradation is efficient 3 - limit bone degradation 4 - able to degrade osteoblasts

Answer 52

2 - ensure bone degradation is efficient - lysosomes contain hyaluronic acid for degrading bone - ruffled surface provides increased surface area for bone breakdown

Question 53

What was the diagnosis of hypercalcaemia given in the lecture? 1 - 0.15mg/100ml 2 - 15mg/100ml 3 - 1.5mg/100ml 4 - 150mg/100ml

Answer 53

2 - 15mg/100ml

Question 54

What is the difference between rickets vs osteomalacia?

Answer 54

- rickets = impaired bone mineralisation in children | - osteomalacia = impaired bone mineralisation in adults

Question 55

When a bone is placed under stress micro-cracks may appear. Osteoblasts then secrete what that is able to stimulate nearby monocytes into differentiating into osteoclasts? 1 - IL-2 and M-CSF 2 - M-CSF and IL-6 3 - RANK-L and M-CSF 4 - IL-6 and RANK-L

Answer 55

3 - RANK-L and M-CSF

Question 56

When a bone is placed under stress micro-cracks may appear. Osteoblasts then secrete RANK-L and M-CSF, which bind with the receptors on which cell of myeloid cell lineage? 1 - monocytes 2 - macrophage 3 - neutrophil 4 - basinophil

Answer 56

1 - monocytes

Question 57

When a bone is placed under stress micro-cracks may appear. Osteoblasts then secrete RANK-L and M-CSF, which bind with the receptors on monocytes. The RANK-L and M-CSF then stimulates these monocytes and they fuse together to form what type of cell? 1 - giant cell 2 - macrophage 3 - osteoclast 4 - osteoblast

Answer 57

3 - osteoclast - these can then degrade bone, releasing Ca2+ and phosphate into the blood https://www.youtube.com/watch?v=Ei4seya3dOg

Question 58

In order to control the level of RANK-L and M-CSF released by osteoblasts and ensure there is not too much osteoclasts activity, what else do osteoblasts secrete that is able to bind with RANK-L and M-CSF, inhibiting their ability to bind with further receptors on monocytes? 1 - IL-2 2 - osteoprotegerin 3 - M-CSF 4 - TNF-a

Answer 58

2 - osteoprotegerin | - act to inhibit RANK-L and M-CSF

Question 59

Once osteoclasts have completed their function, and osteoprotegerin have been able to inhibit RANK-L, how are osteoclasts removed? 1 - become monocytes again 2 - engulfed by macrophages 3 - undergo apoptosis 4 - embedded in bone matrix

Answer 59

3 - undergo apoptosis

Question 60

Once osteoclasts have completed their function, and osteoprotegerin have been able to inhibit RANK-L, osteoblasts begin laying down osteoid seam. What is then deposited on the osteoid seam that will form hydroxyapatite? 1 - Cl- and phosphate 2 - Ca2+ and phosphate 3 - K+ and phosphate 4 - Na+ and phosphate

Answer 60

2 - Ca2+ and phosphate

Question 61

If an osteoblasts gets trapped in the bony matrix that is being laid down, what do these osteoblasts then become?

Answer 61

- osteocytes