What occurs in the proximal convoluted tubule (PCT) of the kidney?

In the proximal convoluted tubule (PCT) of the kidney, reabsorption is the primary process that occurs. This segment of the nephron is responsible for reclaiming a significant portion of solutes and water that were initially filtered out of the blood in the glomerulus. Approximately 65-70% of filtered sodium, chloride, and bicarbonate ions are reabsorbed here, along with a large amount of water, glucose, and amino acids.

The proximal convoluted tubule is highly efficient due to its extensive microvilli, which greatly increase the surface area for absorption. The reabsorbed substances then enter the peritubular capillaries, which surround the PCT, allowing them to return to the bloodstream. Consequently, this process plays a crucial role in maintaining the body’s fluid and electrolyte balance, as well as ensuring that essential nutrients are not lost in urine.

Other options point to different kidney functions not performed specifically in the PCT. Substances are secreted into urine primarily in the distal convoluted tubule (DCT) and collecting duct. Filtration of blood takes place in the glomerulus, and hormone production is associated with other structures like the kidneys or adrenal glands, rather than the