[24] Bone and Fracture Physiology Flashcards

1
Q

What is bone made up of?

A

Cells

Matrix

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2
Q

What cells are found in bone?

A

Osteoblasts
Osteoclasts
Osteocytes
OPCs

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3
Q

What are the components of bone matrix?

A

Organic (osteoid)

Inorganic

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4
Q

What proportion of the bone matrix is organic?

A

40%

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5
Q

What is the organic component of the bone matrix made up of?

A

Collagen type I

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6
Q

What are the properties of the organic component of the bone matrix?

A

Resists tension, twisting, and bending

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7
Q

What % of the bone matrix is inorganic?

A

60%

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8
Q

What is the inorganic component of the bone matrix made up of?

A

Calcium hydroxyapatite

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9
Q

What are the properties of the inorganic component of the bone matrix?

A

Resists compressive forces

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10
Q

What are the classifications of different types of bone?

A

Woven bone

Lameller bone

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11
Q

What is woven bone?

A

Disorganised bone that forms the embryonic skeleton and fracture callus

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12
Q

What is lamellar bone?

A

Mature bone

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13
Q

What are the two types of lamellar bone?

A

Cortical/compact

Cancellous/trabecular

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14
Q

What does the cortical lamellar bone form?

A

The dense outer layer

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15
Q

What does the cancellous lamellar bone form?

A

The porous central layer

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16
Q

How does bone form?

A

Intramembranous ossification

Endochondral ossification

17
Q

What is intramembranous ossification?

A

Direct ossification of mesenchymal bone models formed during embryonic development

18
Q

What bone is formed by intramembranous ossification?

A

Skull bones
Mandible
Clavicle

19
Q

What happens in endochondral ossification?

A

Mesnechyme -> cartilage -> bone

20
Q

Do most bones form by endochondral ossification or intramembranous ossification?

A

Endochondral

21
Q

What are the phases in fracture healing?

A

Reactive phase
Reparative phase
Remodelling phase

22
Q

When does the reactive phase of fracture healing occur?

A

Injury time - 48 hours

23
Q

What happens in the reactive phase of fracture healing?

A

There is bleeding into the fracture site, causing a haematoma, and there is inflammation

24
Q

What happens in the ‘inflammation’ in the reactive phase of fracture healing?

A

Cytokines, growth factors, and vasoactive mediators are released, leading to recruitment of leukocytes and fibroblasts, leading to granulation tissue

25
When does the reparative phase of fracture healing occur?
2 days to 2 weeks
26
What happens in the reparative phase of fracture healing?
Proliferation of osteoblasts and fibroblasts leads to cartilage and woven bone formation, leading to callus formation. Consolidation (endochondrial ossification) of woven bone forms lamellar bone
27
When does the remodelling phase of fracture healing occur?
1wk - 7 years
28
What happens in the remodelling phase of fracture healing?
Remodelling of lamellar bone to cope with mechanical forces applied to it
29
How long does a simple fracture take to heal?
3 weeks
30
What are considered 'complicating factors' in fracture healing?
Adult Lower limb Diaphyseal Open
31
By how much does a 'complicating' factor increasing fracture healing time?
Doubles it