Which part of the nephron is primarily responsible for water reabsorption?

The proximal convoluted tubule is primarily responsible for water reabsorption in the nephron. This segment of the nephron plays a crucial role in the reabsorption of approximately 65-70% of the filtered water, along with a significant amount of solutes such as sodium, glucose, and amino acids. The cells lining the proximal convoluted tubule contain numerous microvilli, which increase the surface area for absorption and are equipped with various transport proteins that facilitate the movement of water and solutes back into the bloodstream.

Water reabsorption in the proximal convoluted tubule occurs through both passive and active processes. The osmotic gradient created by the reabsorption of solutes leads to passive reabsorption of water via osmosis. This process is vital for maintaining fluid balance and preventing dehydration, which underscores the critical role of the proximal convoluted tubule in overall kidney function.

In comparison, other parts of the nephron, such as the glomerulus and Bowman's capsule, are primarily involved in the filtration of blood rather than reabsorption. The distal convoluted tubules also play a role in reabsorption, but to a lesser extent than the proximal convoluted tubule and generally under hormonal control. Thus,