What is the primary site of waste product removal and nutrient reabsorption in the nephron?

The primary site of waste product removal and nutrient reabsorption in the nephron is the proximal convoluted tubule. This part of the nephron plays a crucial role in the renal system by reabsorbing approximately 65-70% of the filtered sodium and water, as well as the majority of essential nutrients such as glucose, amino acids, and bicarbonate. The proximal convoluted tubule's epithelial cells contain numerous microvilli, which increase the surface area available for absorption, making it highly efficient in reclaiming valuable substances from the filtrate back into the bloodstream.

In contrast, the loop of Henle is primarily involved in concentrating urine and regulating water balance rather than nutrient reabsorption. The renal corpuscle is responsible for filtering blood to form urine but does not engage significantly in reabsorption. The collecting duct plays a role in the final concentration of urine and the regulation of water and electrolyte balance, but it is not where the majority of nutrient reabsorption occurs. Hence, the proximal convoluted tubule is rightly identified as the main site for these critical functions within the nephron.