Why does filtrate osmolality decrease in the ascending limb of Henle within the nephron?

💡 Explanation

The filtrate osmolality decreases in the ascending limb because the active transport of NaCl out of the filtrate into the medullary interstitium occurs. This active transport reduces the solute concentration in the filtrate; therefore, the osmolality decreases, rather than increasing due to water influx or urea secretion.

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