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35 Cards in this Set
- Front
- Back
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what is bone remodelling
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coordinated osteoclastic resorption and osteoblastic proliferation
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annual rate of cortical bone turnover
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4%
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annual rate of trabecular bone turnover
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25%
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direction of bone growth
endochondral ossification |
longtitudinal
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direction of bone growth
subperiosteal apposition |
width
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rate of bone remodelling depends on 3
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-growth
-hormones and biochemical factors -mechanical stress |
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organic portion of bone comprised of
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type 1 collagen
proteoglycans osteocalcin cytokines/interleukins |
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woven bone
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-collagen fibres and cells - no specific arrangement
-temporary -froms on fibrous tissue -immature -healing |
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lamellar bone
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-mature bone
-parallel collagen fibres -osteocytes organised -laid on existing bone surface |
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two forms of lamellar bone
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cortical
cancellous |
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puberty to age 30 bone mass
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increases
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after 35-40 bone mass
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loss by about 0.3 -0.5% per year
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post menopause bone loss
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2-3% per year for next 8-10 yrs
slows to 0.5% after age 60 |
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5 determinant of loss of bone mass
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-calcium and phosphates
-PTH -Vit D3 -oestrogen and other sex hormones -calcitonin |
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factors affecting bone turnover
insulin-like growth factor |
increased osteoblast proliferation
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factors affecting bone turnover
TGF |
transforming growth factor
increased osteoblast activity |
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factors affecting bone turnover
IL-1/osteoclast activating factor |
increases osteoclast activity
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factors affecting bone turnover
prostaglandins |
-increased bone turnover
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BMP
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bone morphgenetic proteins
bone formation |
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metabolic bone disorders 2
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-abnormalities of formation
-metabolism of bone |
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metabolic bone disorder pathology 5
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loss of mineralisation
low bone mass high bone mass high bone turnover low bone turnover |
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loss of mineralisation eg
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osteomalacia/rickets
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low bone mass eg
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osteoporosis, osteogenesis imperfecta
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highbone mass eg
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osteopetrosis
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high bone turnover
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pagets,
hyperparathyroidism, thyrotoxicosis |
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low bone turnover
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adynamic disease
hypophosphatasia |
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assessment for metabolic bone disorder
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history
exam xrays DEXA biochemistry bone biopsy (rare) |
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metabolic bone disorder biochemical tests 7
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serum calcium
serum phosphate PTH vit D (measured by 25 HCC) specific endocrine test markers of bone turnover FGF-23 |
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paget's disease features 6
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rapid bone turnover
resorption and formation increased disorganised structure reduced bone strength risk of fracture linked to osteosarcoma tumour suppressor gene |
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osteoporosis features 5
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reduced total bone mass
adequate mineralisation of present osteoid many factors oestrogen deficiency relatively increased bone resorption |
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corticosteroid induced osteoporosis features 4
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increased osteoclast acivity
decreased osteoblast activity impaired collagen formation increased bone turnover and poor bone formation and healing |
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osteopetrosis features 4
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decreased turnover
unregulated (not necessarily increased) osteoblast activity impaired osteoclast activity dense but weak bones |
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fluorosis
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flouride replaces calcium in the matrix
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primary hyperparathyroidism features 4
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unregulated PTH secretion
hyercalcaemia (and low phosphate) markedly increased bone turnover may retain bone mass but osteoprosis in elderly |
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types of rickets 7
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nutritional rickets
congenital rickets rickets of prematurity genetic rickets neoplastic rickets hypophosphataemic rickets drug induced rickets |
