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45 Cards in this Set
- Front
- Back
What percentage of calcium is free (unbound/ionised) in serum? |
47% |
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What percentage of calcium is bound to albumin in serum? |
47% |
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What percentage of calcium in complexed in serum? |
6% |
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Are calcium feedback mechanisms regulated by free, bound or complexed calcium? |
free |
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Which fraction of calcium in serum - free, bound or complexed - is physiologically most important? |
free |
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What is the normal reference range for serum calcium? |
2.2-2.6 mmol/L |
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What is the equation used for adjusting calcium? |
Ca (adj) = Ca (tot) + [0.02(45-alb)] |
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What are the four main organs involved in calcium homeostasis? |
Gut (GI tract) Kidney Bone Parathyroid glands (calcium-sensing receptors) |
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What are the three main hormones involved in calcium metabolism? Do they increase or decrease calcium? |
parathyroid hormone - increase 1, 25 hydroxyvitamin D (calcitriol) - increase calcitonin - decrease |
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How much calcium is exchanged between bones and serum per day? |
8 mmol/day |
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Approximately, how much calcium is absorbed into plasma via the gut per day? |
6 mmol/day |
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How much calcium is filtered from the plasma into the kidneys per day? How much calcium is reabsorbed from the kidneys into the plasma per day? |
240 mmol/day 234 mmol/day |
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Which organ(s) does PTH act on to regulate calcium? |
Bone and kidney |
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Which organ(s) does 1, 25 hydroxyvitamin D act on to regulate calcium? |
Bone and gut |
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Where is most calcium absorbed in the body? |
Small intestine (duodenum and jejunum) |
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Calcium is reabsorbed in different proportions at different regions of the nephron. State where reabsoption occurs and in what percentages. |
proximal convoluted tubule (65%) thick ascending loop of Henle (20%) distal convoluted tubule (15%) |
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Which regions of the nephron responsible for calcium reabsorption are affected by PTH and which are not? |
proximal convoluted tubule - not affected by PTH ascending loop of Henle - affected by PTH distal convoluted tubule - affected by PTH |
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Where are the parathyroid glands located? |
Neck |
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What regulated PTH secretion? |
increase/decrease of free calcium in serum |
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How is calcium detected by the parathyroid glands? |
calcium-sensing receptors on the parathyroid cells |
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What type of receptor is the calcium-sensing receptor? |
G protein-coupled receptor |
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Which drug mimics calcium to reduce PTH concentrations? |
cinicalcet |
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Describe the hormonal change which occurs when there is a small change in ionised calcium. |
Significant, inverse change in PTH |
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What are the three functions of PTH |
(1) calcium reabsorption in renal tubules (2) promotes bone resorption (3) stimulates production of 1, 25 dihydroxyvitamin D (calcitriol) in kidney (which increases calcium absorption in the gut) |
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In which organs does 1, 25 dihydroxyvitamin D (calcitriol) influence calcium homeostasis? |
Bone and gut |
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In which organs does PTH influence calcium homeostasis? |
bone and kidney |
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In what form is vitamin D attained from through diet and sunlight, and where is it metabolised? |
cholecalciferol (vitamin D3) liver |
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What is the product of the conversion of cholecalciferol (vitamin D3)? |
25 hydroxyvitamin D (25 hydroxycholecalciferol) (calcefediol) |
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(1) Which form of vitamin D is converted in the liver? (2) What form of vitamin D is it then converted to in the kidney? |
25 hydroxyvitamin D (25 hydroxycholecalciferol)(calcefediol) is converted in the liver.
It is then converted in the kidney to 1, 25 hydroxyvitamin D (1, 25 hydroxycholecalciferol) (calcitriol) |
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Describe what would happen to calcium and PTH due to hyperparathyroidism |
both would increase |
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Describe what would happen with the production of PTH reelated peptide due to malignancy? |
calcium increased PTH suppressed |
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What percentage of phosphate is in the mineralised matrix of bone? |
85% |
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What percentage of phosphate is inorganic? |
30% |
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What percentage of phosphate is found in extracellular fluids? |
1% |
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Give an example of a physiological process which causes extracellular phosphate to enter cells? |
Insulin-mediated entry of glucose into cells |
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What are the main organs involved in phosphate homeostasis? |
Kidney, gut and bone |
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What are then main hormones involved in phosphate homeostasis? |
PTH Fibroblast Growth Factor 23 (FGF23) 1, 25 dihydroxyvitamin D |
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Roughly, how much phosphate is exchanged between the bones and plasma per day? |
7mmol/day |
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Roughly, how much phosphate is exchanged between the gut and plasma per day? |
Absorbed into plasma: 32mmol/day Released into gut: 7mmol/day |
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Roughly, how much phosphate is filtered/reasbsorbed through the kidneys per day? |
Filtered: 160mmol/day Reabsorbed: 135mmol/day |
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Roughly, how much phosphate is excreted per day? |
20mmol/day |
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Roughly, how much phosphate is lost in urine per day? |
25mmol/day |
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What percentage of proteins is bound to proteins? |
15-20% |
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Where, and in what percentages, is phosphate reabsorbed in the kidneys? |
Proximal convoluted tubule: 75-80% Distal convoluted tubule: 20-25% |
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What are the two main hormones which suppress phosphate reabsorption in the kidneys? |
PTH Fibroblast Growth Factor 23 (FGF23) |