What is the major site for the removal of non-filtered substances in the kidneys?

The proximal convoluted tubule is the major site for the removal of non-filtered substances in the kidneys due to its extensive reabsorption capabilities and secretion processes. This segment of the nephron is particularly important for the reabsorption of water, ions, and various organic molecules such as glucose and amino acids.

Additionally, the proximal convoluted tubule actively secretes substances that were not filtered through the glomerulus, including certain drugs and metabolic waste products. This dual role of reabsorption and secretion makes it the primary site for handling the non-filtered solutes, ensuring that they are removed from the bloodstream effectively.

While the distal convoluted tubule and collecting duct have roles in reabsorption and secretion as well, their functions are more specialized and less involved in the initial removal of non-filtered substances compared to the proximal convoluted tubule. The glomerulus primarily focuses on the filtration of blood and does not play a role in reabsorption or the removal of substances after filtration.