The glomerular filtrate in the loop of Henle gets concentrated in the descending and then gets diluted inthe ascending limbs. Explain

The Loop of Henle, a part of the nephron in the kidney, plays a crucial role in the concentration of urine. It has two parts: the descending limb and the ascending limb, and the process of urine concentration occurs in two steps:

1. Concentration in the Descending Limb: The descending limb of the Loop of Henle is permeable to water but not to salts. As the glomerular filtrate (the fluid part of the blood that enters the nephron) travels down this limb, it enters a region of the kidney medulla that has a high concentration of salts. Due to osmosis, water moves out of the filtrate and into the medulla, making the filtrate more concentrated.

2. Dilution in the Ascending Limb: The ascending limb of the Loop of Henle is impermeable to water but permeable to salts. As the now concentrated filtrate moves up this limb, it enters a region of the kidney medulla that has a lower concentration of salts. This causes salts to move out of the filtrate and into the medulla, making the filtrate more dilute.

This counter-current mechanism in the Loop of Henle helps in maintaining a high concentration of salts in the kidney medulla, which is essential for the kidney's ability to produce concentrated urine and thus conserve water.