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21 Cards in this Set
- Front
- Back
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% of bone organic % of bone inorganic |
35% organic 65% inorganic |
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components and function of organic bone |
collagen and proteoglycans gives flexible strength |
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components and function of inorganic bone |
hydroxyapite i.e. calcium phosphate crystals stores calcium and phosphate in body give compressional strength |
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% of calcium in plasma, % in intracellular fluid |
0.1% in plasma, 0.9% in ICF |
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% composition of plasma calcium |
45% ionized 45% protein bound 10% soluble complexes |
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how fast can body return plasma calcium concentration back to normal |
30-60mins |
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% of phosphorous in bone |
85-90% |
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form of phosphorous in soft tissues |
organic phosphates e.g. phospholipids, proteins, nucleic acids |
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half life of parathyroid hormone |
less than 5 mins |
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what happens when calcium levels drop in ECF? |
Ca-sensing receptors send signal to chief cells to increase circulating PTH (only needs to drop 0.1 mmol) |
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what does PTH inhibit to increase osteoclast activity? |
osteoprotegerin (which normally inhibits RANKL), preventing osteoprotegerin allows RANKL to increase osteoclasts activity leading to increased calcium concentration |
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where do vitamin D2, D3 and 1,25 dihydroxyvitamin D (DVD) come from? |
D2- diet D3- synthesized in skin by UVB light DVD is metabolite of D2 and D3 |
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what happens if hypocalcemia? |
hyper excitability of nerves tetany |
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what happens if hypercalcemia? |
muscle weakness, lethargy, depression |
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two forms of calcium in bone |
1. readily exchangeable pool (for buffering) 2. larger stable pool (for bone remodelling) |
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relationship between intestine and kidney in regard to calcium |
amount absorbed in intestine, is approx amount excreted in kidney |
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effect of PTH on bone, intestine, kidney |
bone: increase osteoclast activity/ Ca resorption intestine: stimulate production of DVD (indirectly stimulate Ca absorption) kidney: stimulate phosphate excretion and Ca reabsorption |
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calcitonin, where does it come from, what does it do, what is it used for?
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from C cells in parafollicular thyroid increase Ca deposition in bone by inhibiting osteoclasts used to treat Paget's disease of bone and osteoporosis |
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effect of DVD on Ca |
intestine: increase Ca absorption |
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what causes Ricket's |
lack of DVD induced absorption of Ca from intestines - leads to hypocalcemia in children |
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what is Paget's disease of bone? |
excess osteoclast activity (bone breakdown) and disorganized remodelling localized |
