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Ageing > Osteoporosis > Flashcards

Osteoporosis Flashcards

1
Q

Trabecular bone

A

Space for marrow storage, strength and lightness

At the ends of long bones and the inner part of short/flat/irregular bones

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2
Q

Cortical bone

A

Most of mature skeleton, compact bone laid down concentrically around Haversian canals

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3
Q

osteogenic cells

A

unspecialised cells from mesenchyme that undergo cell division to form osteoblasts

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4
Q

osteoblasts

A

bone-forming cells derived from stroll cells that synthesise and secrete much of bone matrix - also have high ALP

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5
Q

osteoclasts

A

from monocytes, carry out bone resorption sue to acidic pH and proteolytic enzymes

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6
Q

osteocytes

A

mature bone cells formed from osteoblasts which maintain cellular activities within bone

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7
Q

diagnosing osteoporosis

A
  • Dual energy X-ray absorptiometry (DEXA) which assesses bone mineral density
  • Osteoporosis is BMD T score of -2.5 or less at either lumbar spine or femoral neck
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8
Q

What is a z score?

A
  • Z-score: (patients BMD - age-matched mean) / age-matched SD
  • Assesses bone loss compared to expected bone loss for age-matched peers
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9
Q

What is a T score?

A
  • T score: (patient’s BMD - young adult mean) / young adult SD
  • T score is most important
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10
Q

osteopenia T score boundaries

A

-1 to -2.5

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11
Q

MOA biphosphonates

A

inhibit bone resorption and decrease osteoclast activity

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12
Q

E.g. biphosphonates

A

alendrotnic acid, risedronate sodium

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13
Q

raloxifene MOA

A

Selective estrogen receptor modulator = decreased bone resorption and increase bone mineral density
HRT = increase osteoblast activity

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14
Q

denosumab MOA

A

monoclonal antibody

inhibits osteoclast formation and decreases bone resorption

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15
Q

periosteum

A

outer fibrous layer where tendons attach, inner cellular layer of stem cells

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16
Q

cortical bones

A

most bones, supports posture, stein’s

17
Q

trabecular bone

A

ends of long bones, scapulas, ribs and vertebral bodies - bone marrow stored here

18
Q

osteons

A
  • Lamellae; collagen and calcium phosphate (hydroxyapatite)
  • Haversian canals: neurovascular supply
  • Medullary canal: inside trabecular bone containing bone marrow
19
Q

How do osteoblasts activate osteoclasts

A

Osteoblasts detect stress fractures that need resorbing so make RANK-L

Monocytes have RANK receptors - fuse together - form osteoclast

20
Q

What do osteoclasts release?

A
  • Collagenase

- HCl (breaks down calcium phosphate)

21
Q

How are stress fractures repaired?

A

Osteoblasts detect stress fractures that need resorbing so make RANK-L

Monocytes have RANK receptors - fuse together - form osteoclast

Osteoclast resorb bone by producing:

  • Collagenase
  • HCl (breaks down calcium phosphate)

After this, osteoclasts apoptose

Osteoblasts secrete osteoprotegerin which binds to RANK-L so fewer osteocytes are made

Osteoblasts secrete collagen and deposit calcium phosphate again

Osteoblasts turn into osteocytes when done

22
Q

response to hypocalcaemia

A

increased PTH
osteoblasts make RANK-L
monocytes combine to create an osteocyte
osteocytes break down collagen and release calcium and phosphate
increased serum calcium and phosphate ions
calcium and phosphate bind to PTH causes renal excretion of phosphate to increase amount of free calcium

23
Q

response to hypercalcaemia

A

decreased PTH
decreased bone resorption
hypercalcaemia
increased calcitonin produced by parafollicular c cells in thyroid
decreased osteoclast activity and increased osteoblast activity
decreased bone resorption and increased calcium deposition

24
Q

osteoporosis

A
  • Bone is resorbed by osteoclasts quicker than it is rebuilt by osteoblasts
  • Decreased bone density but normal bone
  • Peak bone mass in 20s then declines, faster during menopause
25
Q

risk factors for osteoporosis

A
  • Decreased oestrogen - late period or early menopause
  • White people
  • Hypocalcaemia
  • Drinking and smoking
  • Steroids
  • No exercise
26
Q

types of osteoporosis

A
  • Post-menopausal: reduced oestrogen increases bone resorption (>50)
  • Senile: osteoblasts can’t build but continue to activate osteoclasts (>80)
27
Q

diagnosing osteoporosis

A
  • Fragility fractures

- DEXA scan

28
Q

treatments of osteoporosis

A
  • Vit D - colecalciferol
  • Calcium carbonate
  • Biphosphonates: alendronic acid - increased risk of oesophagitis
29
Q

what happens to PTH levels in hypercalacaemia

30
Q

what happens to osteoblasts in hypocalcaemia

A

osteoblasts activate osteoclasts

31
Q

what happens to phosphate levels in raised PTH

A

kidney excretes so phosphate levels fall

32
Q

what does small bowel do when vit D levels rise

A

increase calcium absorption

Ageing (21 decks)

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