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In page Countercurrent exchange:

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  • Loop of Henle Ascending: after the tip (or 'bend') of the loop, the liquid flows in the thin ascending limb.[6][citation needed] Salt–sodium Na+ and chloride Cl ions are pumped out of the liquid[7][citation needed] gradually lowering the concentration in the exiting liquid, but, using the countercurrent multiplier mechanism, always pumping against a constant and small osmotic difference.