lecture 17 Renal Principles sq key

lecture 17 Renal Principles sq key - Short Answers to Study...

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Short Answers to Study Questions for Lecture 17 1. The Greening of the Kidney The renal system operates by filtering the plasma, then reabsorbing most of the substances it has just filtered. Reabsorption is often an active process, and is very costly. For example, over 99% of the sodium that is filtered is reabsorbed, and reabsorption of sodium costs 80% of the kidneys’ energy budget. a. As only about 0.5% of the filtered Na + is not reabsorbed, maybe the best way to save energy in the kidney would be to not filter Na + at all, but to leave all of it in the plasma. What would be the consequence of this plan? Given the high Na + intake of many of us, this plan would lead to accumulation of sodium, consequent increase in plasma volume, and very high blood pressure. b. 65% of the Na is reabsorbed in the proximal tubule. Another way to ‘green’ the kidney would be to leave this 65% in the blood. Could you design a renal filter that filters only part of the plasma sodium? By inserting the appropriate number of Na pores into a membrane that is otherwise impermeable, and inserting the membrane in each glomerular capillary, one could achieve limited filtering of Na. Of course, the membrane would need to also be very permeable to most of the other substances filtered by the kidneys. This is an idea that isn’t ready for
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lecture 17 Renal Principles sq key - Short Answers to Study...

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