Final answer:
The structure of a nephron encourages the concentration of urine through countercurrent multiplication in the loop of Henle and Vasa recta.
Step-by-step explanation:
The structure of a nephron encourages the concentration of urine through a process called countercurrent multiplication. This process occurs in the loop of Henle and vasa recta, which are important components of the nephron.
The loop of Henle is responsible for creating a concentration gradient in the medulla of the kidney. The descending limb of the loop is permeable to water, allowing water to passively diffuse out of the nephron. The ascending limb, on the other hand, is impermeable to water but actively pumps out ions.
The vasa recta is a network of blood vessels that runs parallel to the loop of Henle. It acts as a countercurrent exchanger, allowing the reabsorption of water and ions. This helps to maintain the concentration gradient established by the loop of Henle, resulting in the concentration of urine.