Question

${\text{Na}}^{+}$ and ${\text{Cl}}^{-}$ transported out of the tubules to help set up the countercurrent multiplier. Which of the following are sites of active ${\text{Na}}^{+}$ and ${\text{Cl}}^{-}$ transport in the nephron?

• A. Proximal tubule, ascending limb of the loop of Henle
• B. Descending limb of the loop Henle, ascending limb of the loop of Henle
• C. Ascending limb of the loop of Henle, proximal tubule
• D. Collecting duct, descending limb of the loop of Henle

Answer 1

The correct option is A Proximal tubule, ascending limb of the loop of Henle

The proximal tubule is the site of active transport of ${\text{Na}}^{+}$ out of the tubule. ${\text{Na}}^{+}$ also moves out of the tubule at the ascending limb of the loop of Henle, but this is a passive transport with ${\text{Cl}}^{-}$ being actively transported out.