What is the primary function of the Loop of Henle in the kidneys?

The primary function of the Loop of Henle in the kidneys is not to increase surface area for absorption, but rather to play a critical role in the concentration of urine. The Loop of Henle is responsible for creating a concentration gradient in the medulla of the kidney, which allows for the reabsorption of water and solutes.

As the filtrate passes through the descending limb of the Loop of Henle, water is reabsorbed due to the higher osmolarity of the surrounding interstitial fluid. In the ascending limb, sodium and chloride ions are actively transported out, which contributes to this osmotic gradient. This process is essential for the kidneys to produce concentrated urine, enabling the body to conserve water and maintain homeostasis.

Furthermore, the Loop of Henle's function is integral to the overall function of the nephron, which includes filtration of blood, regulation of blood pH, and the secretion of hormones, none of which directly reflect the Loop of Henle's primary role.