Final answer:
The proximal convoluted tubule (PCT) of the nephron is the site where the highest percentage of sodium and water is reabsorbed into the bloodstream, accounting for about 67% of resorption.
Step-by-step explanation:
The location where the highest percentage of sodium and water are reabsorbed back into the bloodstream is the proximal convoluted tubule (PCT) of the nephron. About 67 percent of the water, Na+, and K+ that enters the nephron is reabsorbed here and returned to the circulation. The PCT also recovers almost 100 percent of glucose, amino acids, and other organic substances such as vitamins. Water reabsorption continues as the filtrate moves through the nephron, with additional amounts being reabsorbed in the distal convoluted tubule (DCT) and the collecting ducts, but it is the PCT that is primarily responsible for the bulk of sodium and water reabsorption.