Which segment of the nephron loop is permeable to water?

• A. Collecting duct
• B. Ascending limb
• C. Distal convoluted tubule
• D. Descending limb

Answer: (D)

Verified step by step guidance

1. Understand the structure of the nephron, which is the functional unit of the kidney. It consists of several segments, including the proximal convoluted tubule, nephron loop (loop of Henle), distal convoluted tubule, and collecting duct.
2. Identify the segments of the nephron loop: the descending limb and the ascending limb. Each has distinct properties regarding permeability to water and solutes.
3. Recall that the descending limb of the nephron loop is permeable to water but not to solutes. This allows water to be reabsorbed into the bloodstream, concentrating the urine.
4. Contrast this with the ascending limb, which is impermeable to water but actively transports ions like sodium and chloride out of the filtrate, further concentrating the urine.
5. Recognize that the distal convoluted tubule and collecting duct have different roles in reabsorption and secretion, but the descending limb is specifically known for its permeability to water.