Imagine a water molecule has just entered the proximal convoluted tubule of the nephron that will eventually be part of the urine. What parts of the nephron will it travel through (in order) before it reaches the renal pelvis?

Explanation

To determine the pathway of a water molecule through the nephron before it reaches the renal pelvis, we can break down the journey into distinct steps:

1. **Proximal Convoluted Tubule (PCT)**: The water molecule first enters the proximal convoluted tubule. This is where a significant amount of reabsorption occurs, but for the purpose of this question, we focus on the water's journey.

2. **Descending Limb of the Loop of Henle**: After the PCT, the water molecule moves into the descending limb of the loop of Henle. This segment is permeable to water, allowing further reabsorption.

3. **Ascending Limb of the Loop of Henle**: Next, the water molecule travels into the ascending limb of the loop of Henle. This segment is impermeable to water, but it actively transports ions out, which helps in the concentration of urine.

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