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Diseases > Bones > Flashcards

Bones Flashcards

1
Q

What is the mechanical role of bone?

A

Structural support and muscle attachment

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2
Q

What is the protective role of bone?

A

Protects vital organs

Bone marrow

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3
Q

What is the metabolic role of bone?

A

Ion homeostasis

Calcium and phosphate

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4
Q

What is bone?

A

Specialised connective tissues
Extracellular matrix calcifies
30% organic: collagen and non-collagenous protein
70% inorganic: calcification, formation of hydroxyapatite

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5
Q

What are the cells within bone?

A

Osteoclasts
Osteoblasts
Bone lining cells
Osteocyte

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6
Q

What is an osteoclast?

A

Bone resorption

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7
Q

What is an osteoblast?

A

Bone forming

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8
Q

What are bone lining cells?

A

Specialist inactive osteoblastlast

Initiate bone forming

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9
Q

What are osteocytes?

A

Mechanosensing cells

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10
Q

What is the basic structure of bone?

A

Cortical, compact bone
Spongy, trabecular bone
Surrounded by periosteum

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11
Q

What do osteoblasts do?

A

Formation of bone matrix
Regulation of mineralisation
Regulation of osteoclast differentiation
Precursors of bone living cells and osteocytes

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12
Q

What do osteoblasts differentiate from?

A

Stromal precursor cells

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13
Q

What do osteoblasts express?

A

RUNX2 and Osx

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14
Q

How do osteoblasts differentiate?

A 
Unknown
HOX genes
Bone morphogenic proteins
Wnt
PTH
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15
Q

What can protect against osteoblast apoptosis?

A

Intermittent PTH

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16
Q

What do osteoclasts do?

A

Bone resorption

Calcium homeostasis

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17
Q

What do osteoclasts develop from?

A

Arise from mononuclear cells

Either from the marrow or circulating monocytes

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18
Q

What signals are necessary for osteocyte differentiation?

A

Macrophage colony stimulating factor

RANKL

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19
Q

What is the order of osteoclast differentiation?

A 
Bone marrow precursor
Pre-osteoclast
Proliferate
Fused prokaryon
Active osteoclast
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20
Q

What does an active osteoclast express?

A

F4/80 -ve
Trap +ve
CTR +ve
Beta3 +ve

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21
Q

How do osteoclasts function?

A 
Move by chemotaxis
Cell is highly polarised
Creates a sealed environment
Secretes acids and enzymes
Bone is resorbed by combination of enzymes
Forms a Howships lacuna
22
Q

What is the RANKL/OPG system?

A

Signalling between osteoblasts and osteoclasts
Receptor activator of Nf-kappabeta (RANK) is a receptor on osteoclasts
RANKL produced by osteoblasts and stromal cells and some lymphocytes
RANK+RANKL causes osteoclast differentiation and activation

23
Q

What is osteoprogerin?

A

Osteoprogerin is a dummy receptor for RANKL

24
Q

What happens if over express osteoprogerin?

A

Too much inhibition of bone resorption

Osteopetrosis

25
Q

What can cause osteoporosis?

A

Loss of osteoprogerin

RANKL overexpression

26
Q

What can cause osteopetrosis?

A

Overexpression of osteoprogerin
Absence of RANKL
Absence of RANK

27
Q

Factors increasing RANKL expression?

A

Parathyroid hormone
Oestrogen deficiency
Inflammatory cytokines
Glucocorticoids

28
Q

How do osteocytes form?

A

Osteoblasts are incorporated into the bone matrix
During bone ossification and mineralisation
Integrated into osteocyte network

29
Q

What is the function of osteocytes?

A

Regulation of local mineralisation
Mechanosensing
Initiation of bone remodelling cycle
Sclerostin and BMPs

30
Q

What regulates osteocytes?

A

Shear stress
Damage
Canalicular fluid flow

31
Q

How does bone remodel in trabecular bone?

A

Bone resorption
Formation of osteoid
Osteoid mineralisation
New bone

32
Q

How is cortical bone remodelled?

A

Via the Haversian system

33
Q

What are bone remodelling units?

A

Cutting zone
Reversal zone
Closing cone

34
Q

Where does bone grow?

A

Periosteal surfaces

35
Q

What is the definition of osteoporosis?

A

A progressive systemic skeletal disease
Characterised by low bone mass
Micro-architectural deterioration
Increase in fragility and susceptibility

36
Q

What fractures are common of osteoporosis?

A

Head of ulna wrist fracture (Colles’)
Spinal collapse
Vertebral fractures
Fratured neck of femur

37
Q

What are the causes of osteoporosis?

A

Oestrogen deficiency
Glucocorticoids
Vitamin D/ calcium deficiency
Ageing

38
Q

What does oestrogen do to the skeleton?

A

Maintain skeletal health
Oestrogen deficiency results in increased bone resorption
Oestrogen receptors are expressed in osteoblasts not osteoclasts
Oestrogen deficiency leads to increased expression of RANKL

39
Q

Can oestrogen be used as a therapy?

A 
Oestrogen treatment as HRT
Given by mouth, patch or implant
Reduces bone resorption
Increase bone density
Reduces fracture risk
Complications of DVT, breast cancer, uterine cancer, heart disease and dementia
40
Q

How do SERMs work?

A

Selective oestrogen receptor modulators
Tamoxifen
Increases bone mineral density

41
Q

What is Raloxifene?

A

Increases bone mineral density at all sites
Decreases risk of breast cancer
Cardiovascular risk is uncertain
Partial agonist on bone, decreases BMD in pre-menopausal

42
Q

What are bisphosphonates?

A

Alendronate
Potent inhibitor of bone resorption
Inhibits intracellular signalling pathway
Increases osteoclast apoptosis

43
Q

What are advantages of bisphonates?

A 
Bone selective
Relatively few side effects
Improve cortical and trabecular bone
Once daily/weekly tablet
Equal effect in men and women
44
Q

What are the disadvantages of bisphonates?

A

Incorporated into the skeleton
Unknown long-term effect
Risk of blocking repair of microfractures
Uncommon fractures: diaphyseal of femur

45
Q

Why is vitamin D important?

A

Vitamin D is essential for calcium absorption and osteoblast differentiation

46
Q

What happens if vitamin D is absent?

A

Osteomalacia

Mild deficiency impairs osteoblast function

47
Q

What happens to the parathyroid if calcium is deficient?

A

Secondary hyperparathyroidism
Stimulates osteoclastic activity
Increases resorption
PTH receptors on osteoblasts increase RANKL

48
Q

How can we treat calcium and vitamin D deficiency?

A

Supplementation

49
Q

Whats the effect of hyperparathyroidism?

A

Bone loss due to bone resorption

50
Q

What is the effect of PTH injection?

A

Increased bone formation

Essential in differentiation of osteoblasts

51
Q

What effect do glucocorticoids have on bone?

A

Fracture risk increases with the use of steroids
Decrease activity of osteoblasts
Mitigate osteoclasts
Treated with bisphosphonates or intermittent PTH injection

Diseases (5 decks)

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