Editing Kidney functions
From Iusmphysiology
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*A normal day has about 1440 minutes in it. | *A normal day has about 1440 minutes in it. | ||
*So a normal kidney filters 125 ml plasma / min * 1440 min = 180 L / day. | *So a normal kidney filters 125 ml plasma / min * 1440 min = 180 L / day. | ||
- | **And we have about 3.5 L of | + | **And we have about 3.5 L of plasma (filtered 50 times per day) and 14 L of extracellular fluid (filtered 13 times per day). |
===Filtration fraction=== | ===Filtration fraction=== | ||
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===PAH clearance=== | ===PAH clearance=== | ||
- | *The clearance of | + | *The clearance of p-aminohippurate (PAH) has been shown to model well the renal plasma flow (RPF). |
*Note that PAH is not normally found in blood plasma. | *Note that PAH is not normally found in blood plasma. | ||
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*An '''extraction ratio''' is the amount of a compound entering the kidney versus the amount excreted in the urine. | *An '''extraction ratio''' is the amount of a compound entering the kidney versus the amount excreted in the urine. | ||
*PAH has an extraction ratio of nearly 1, meaning that nearly all of the PAH that enters the kidney gets filtered out into the filtrate urine. | *PAH has an extraction ratio of nearly 1, meaning that nearly all of the PAH that enters the kidney gets filtered out into the filtrate urine. | ||
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===Renal blood flow versus renal plasma flow=== | ===Renal blood flow versus renal plasma flow=== | ||
- | *Renal blood flow and renal plasma flow are not the same value | + | *Renal blood flow and renal plasma flow are not the same value. |
- | * | + | *RBF = RPF / (1 - hematocrit) |
*Recall that a normal renal plasma flow (RPF) is 660 ml plasma / min. | *Recall that a normal renal plasma flow (RPF) is 660 ml plasma / min. | ||
*Recall that a normal plasma / hematocrit ratio is 0.45. | *Recall that a normal plasma / hematocrit ratio is 0.45. |