How is water in the filtrate reabsorbed into the blood during the process of glomerular filtration?

• A. Through active transport in the proximal convoluted tubule
• B. Through bulk flow in the collecting duct
• C. Via facilitated diffusion in the distal convoluted tubule
• D. By osmosis in the proximal convoluted tubule

Answer: (D)

Verified step by step guidance

1. Understand that glomerular filtration is the first step in the process of urine formation, where blood is filtered in the glomerulus to form filtrate.
2. Recognize that the proximal convoluted tubule (PCT) is the first segment of the renal tubule where reabsorption of water and solutes occurs.
3. Identify that water reabsorption in the PCT occurs primarily through osmosis, a passive transport mechanism where water moves from an area of lower solute concentration to an area of higher solute concentration.
4. Note that the reabsorption of solutes like sodium and glucose in the PCT creates an osmotic gradient, which drives the movement of water from the filtrate back into the blood.
5. Conclude that the correct mechanism for water reabsorption in the PCT during glomerular filtration is osmosis, facilitated by the osmotic gradient created by solute reabsorption.