Where does the majority of water and salt reabsorption take place in the nephron?

The majority of water and salt reabsorption in the nephron occurs in the proximal convoluted tubule. This segment of the nephron is responsible for reabsorbing approximately 65-70% of the filtered sodium and a similar percentage of water. The cells lining the proximal convoluted tubule are well-adapted for this reabsorption, possessing numerous microvilli that increase the surface area for absorption and enhance the efficiency of solute and water transport.

The proximal convoluted tubule uses various transport mechanisms, including active transport for sodium and co-transport for glucose and amino acids, which indirectly drives the passive reabsorption of water through osmotic gradients. This reabsorption plays a crucial role in maintaining fluid and electrolyte balance in the body.

In contrast, while the loop of Henle participates in reabsorbing water and salts, its primary function is to create a concentration gradient in the medulla, which is essential for urine concentration. The distal convoluted tubule also contributes to further reabsorption of sodium and water but to a lesser extent than the proximal convoluted tubule. Bowman’s capsule, on the other hand, is primarily involved in the filtration of blood rather than reabsorption. Thus, the proximal