Final answer:
The vasa recta is responsible for the exchange of water, nutrients, and salts in the kidney, playing a key role in maintaining the countercurrent multiplier system and efficient urine concentration. The correct option is a.
Step-by-step explanation:
The structure responsible for the exchange of water, nutrients (glucose, and O2), and salts in the kidneys is the vasa recta. The vasa recta serves a crucial role in regulating the concentration of urine and maintaining the countercurrent multiplier system within the kidney.
As blood travels through the vasa recta, which flows adjacent to the loop of Henle, there is a selective exchange of substances. In the descending limb of the vasa recta, sodium (Na+) and urea enter from the surrounding interstitial fluid while water is reabsorbed into the blood. In the ascending limb, Na+ and urea are secreted while water reenters the blood from the tubular fluid.
This process helps in preventing the loss of too much Na+ and preserving the osmotic gradients required for proper kidney function. The countercurrent mechanism is fundamental for efficient urine concentration and waste removal while preserving necessary solutes and water.
Therefore, the correct option is a.