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Renal urea handling is the part of renal physiology that deals with the reabsorption and secretion of urea.
Urea allows the body to create hyperosmotic urine (urine that has more ions in it--is "more concentrated"--than that same person's blood plasma). Preventing the loss of water in this manner is important if the person's body needs to save water in order to maintain a suitable blood pressure or (more likely,) in order to maintain a suitable concentration of sodium ions in the blood plasma.
About half of the urea filtered (40%[1]) is normally found in the final urine, since there is more reabsorption than secretion along the nephron.
It is regulated by antidiuretic hormone, which controls the amount reabsorbed in the collecting duct system and secreted into the loop of Henle.
Overview table
| Characteristic | proximal tubule | loop of Henle | Distal convoluted tubule | Collecting duct system | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| S1 | S2 | S3 | descending limb | thin ascending limb | thick ascending limb | connecting tubule | initial collecting tubule | cortical collecting ducts | medullary collecting ducts | ||
| reabsorption (% compared to filtered amount) | 50[1] | 70 | |||||||||
| secretion (% compared to filtered amount) | 60[1] | ||||||||||
| reabsorption (mmoles/day) | |||||||||||
| Concentration | |||||||||||
| electrical driving force (mV) | -3[2] | +3[2] | +15[2] | -5 to +5[2] | -40[2] | ||||||
| chemical driving force (mV) | |||||||||||
| electrochemical driving force (mV) | |||||||||||
| apical transport proteins |
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| basolateral transport proteins |
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| Other reabsorption features | |||||||||||
References
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Wikipedia content modification information:
- This page was last modified on 25 February 2008, at 18:58.
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