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| Autor | R. Bowen |
| Titel | Endocrine Control of Calcium and Phosphate Homeostasis |
| Datum | 11. October 2003 |
| Anmerkung | At the bottom pf the page: "Last updated on October 11, 2003 Author: R. Bowen" |
| URL | http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/calcium.html |
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| Fußnoten | no |
| Fragmente | 2 |
| [1.] Dsa/Fragment 039 09 - Diskussion Zuletzt bearbeitet: 2016-08-07 21:02:22 WiseWoman | Bowen 2003, Dsa, Fragment, Gesichtet, KomplettPlagiat, SMWFragment, Schutzlevel sysop |
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| Untersuchte Arbeit: Seite: 39, Zeilen: 9-25 |
Quelle: Bowen 2003 Seite(n): 1 (online source), Zeilen: - |
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| It is critical to maintain blood calcium concentrations within a tight normal range. Deviations above or below the normal range frequently lead to serious diseases. There are three major pools of calcium in the body:
• Intracellular calcium: a large majority of calcium within cells is sequestered in mitochondria and endoplasmic reticulum. Intracellular free calcium concentrations fluctuate greatly, from roughly 100 nM to greater than 1 μM, due to release from cellular stores or influx from extracellular fluid. These fluctuations are integral to calcium's role in intracellular signaling, enzyme activation and muscle contractions. • Calcium in blood and extracellular fluid: roughly half of the calcium in blood is bound to proteins. The concentration of ionized calcium in this compartment is normally almost invariant at approximately 1 mM or 10000 times the basal concentration of free calcium within cells. Also, the concentration of phosphorus in blood is essentially identical to that of calcium. • Bone calcium: a vast majority of body calcium is in bone. Within bone, 99% of the calcium is tied up in the mineral phase, but the remaining 1% is in a pool that can rapidly exchange with extracellular calcium. |
It is critical to maintain blood calcium concentrations within a tight normal range. Deviations above or below the normal range frequently lead to serious disease.
[...] There are three major pools of calcium in the body: • Intracellular calcium: A large majority of calcium within cells is sequestered in mitochondria and endoplasmic reticulum. Intracellular free calcium concentrations fluctuate greatly, from roughly 100 nM to greater than 1 uM, due to release from cellular stores or influx from extracellular fluid. These fluctuations are integral to calcium's role in intracellular signaling, enzyme activation and muscle contractions. • Calcium in blood and extracellular fluid: Roughly half of the calcium in blood is bound to proteins. The concentration of ionized calcium in this compartment is normally almost invariant at approximately 1 mM, or 10,000 times the basal concentration of free calcium within cells. Also, the concentration of phosphorus in blood is essentially identical to that of calcium. • Bone calcium: A vast majority of body calcium is in bone. Within bone, 99% of the calcium is tied up in the mineral phase, but the remaining 1% is in a pool that can rapidly exchange with extracellular calcium. |
The source is not mentioned. |
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| [2.] Dsa/Fragment 040 01 - Diskussion Zuletzt bearbeitet: 2016-08-07 21:06:53 WiseWoman | Bowen 2003, Dsa, Fragment, Gesichtet, KomplettPlagiat, SMWFragment, Schutzlevel sysop |
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| Untersuchte Arbeit: Seite: 40, Zeilen: 1ff (entire page) |
Quelle: Bowen 2003 Seite(n): 1 (online source), Zeilen: - |
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| Three organs participate in supplying calcium to blood and removing it from blood when necessary:
• The small intestine is the site where dietary calcium is absorbed. Importantly, efficient absorption of calcium in the small intestine is dependent on expression of a calcium-binding protein in epithelial cells. • Bone serves as a vast reservoir of calcium. Stimulating net resorption of bone mineral releases calcium and phosphate into blood, and suppressing this effect allows calcium to be deposited in bone. • The kidney is critically important in calcium homeostasis. Under normal blood calcium concentrations, almost all of the calcium that enters glomerular filtrate is reabsorbed from the tubular system back into blood, which preserves blood calcium levels. If tubular reabsorption of calcium decreases, calcium is lost by excretion into urine. The following table summarizes body responses to changes in calcium:
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Three organs participate in supplying calcium to blood and removing it from blood when necessary:
• The small intestine is the site where dietary calcium is absorbed. Importantly, efficient absorption of calcium in the small intestine is dependent on expression of a calcium-binding protein in epithelial cells. • Bone serves as a vast reservoir of calcium. Stimulating net resorption of bone mineral releases calcium and phosphate into blood, and suppressing this effect allows calcium to be deposited in bone. • The kidney is critcally [sic] important in calcium homeostasis. Under normal blood calcium concentrations, almost all of the calcium that enters glomerular filtrate is reabsorbed from the tubular system back into blood, which preserves blood calcium levels. If tubular reabsorption of calcium decreases, calcium is lost by excretion into urine. [...] [...] The following table summarizes body responses to conditions that would otherwise lead to serious imbalances in calcium and phosphate levels in blood.
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The source is not given. |
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