ANATOMY

Detailed explanation-1: -In loop of Henle, water is reabsorbed by the process of osmosis.

Detailed explanation-2: -A large amount of reabsorption occurs in the proximal convoluted tubule. Reabsorption is when water and solutes within the PCT are transported into the bloodstream. In the PCT this process occurs via bulk transport. The solutes and water move from the PCT to the interstitium and then into peritubular capillaries.

Detailed explanation-3: -Most of the solute reabsorbed in the proximal tubule is in the form of sodium bicarbonate and sodium chloride, and about 70% of the sodium reabsorption occurs here. Sodium reabsorption is tightly coupled to passive water reabsorption, meaning when sodium moves, water follows.

Detailed explanation-4: -Water reabsorption is by osmosis through water channels in the membrane. These water channels consist of a family of proteins called aquaporin. At least seven different aquaporin isoforms are expressed in the kidney.

Detailed explanation-5: -The proximal tubule also completes the reabsorption of glucose, amino acids, and important anions, including phosphate and citrate, because it is the sole site of transport of these filtered solutes.