Renal fluid present in the part of renal tubule which is impermeable to water but permeable to salts is

Options

A. Hypertonic to the medullary fluid
B. Hypotonic to the medullary fluid
C. Isotonic to the cortical fluid
D. Hypertonic to blood and isotonic to the cortical fluid

Answer

To answer the question regarding the renal fluid present in the part of the renal tubule which is impermeable to water but permeable to salts, we can break down the solution into a series of steps:

### Step-by-Step Solution:

1. **Understanding the Renal Tubule**: The renal tubule is a part of the nephron in the kidney where the filtration of blood occurs. It consists of various segments, including the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

2. **Properties of the Renal Fluid**: The question specifies that the renal fluid in this part of the renal tubule is impermeable to water but permeable to salts. This means that while salts can pass through the walls of the tubule, water cannot.

3. **Identifying the Relevant Segment**: The segment of the renal tubule that fits this description is the **ascending limb of the loop of Henle**. This part is known for being impermeable to water while allowing the reabsorption of salts (such as sodium and chloride ions).

4. **Understanding Osmotic Conditions**: The renal fluid in the ascending limb is described as being **hypotonic** to the medullary fluid. This means that the concentration of solutes (salts) in the renal fluid is lower than that in the surrounding medullary fluid, causing water to move out of the renal fluid into the medullary fluid.

5. **Conclusion**: Therefore, the renal fluid present in the part of the renal tubule which is impermeable to water but permeable to salts is **hypotonic to medullary fluid**.

### Final Answer:
The renal fluid present in the part of the renal tubule which is impermeable to water but permeable to salts is **hypotonic to medullary fluid**.

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