Which of the following statements in correct ?

Options

A. The ascending limb of loop of Henle is impermeable to water
B. The descending limb of loop of Henle is impermeable to water
C. The ascending limb of loop of Henle is impemeable to water
D. The descending limb of loop of Henle is permeable to electrolytes.

Answer

To determine which statement about the loop of Henle is correct, we need to analyze the functions of its ascending and descending limbs.

### Step-by-Step Solution:

1. **Understanding the Structure**: The loop of Henle is a U-shaped structure in the nephron, which is crucial for the concentration of urine. It consists of two main parts: the descending limb and the ascending limb.

2. **Analyzing the Ascending Limb**:
- The ascending limb of the loop of Henle is known to be impermeable to water.
- This means that water cannot pass through this part of the nephron.
- Instead, this limb actively transports ions such as sodium (Na+), potassium (K+), and chloride (Cl-) out of the filtrate into the surrounding interstitial fluid.

3. **Analyzing the Descending Limb**:
- The descending limb, in contrast, is permeable to water but impermeable to solutes (ions).
- This allows water to be reabsorbed back into the bloodstream while preventing the passage of electrolytes.

4. **Evaluating the Statements**:
- **Statement 1**: "The ascending limb of loop of Henle is impermeable to water." - This statement is correct.
- **Statement 2**: "The descending limb of loop of Henle is impermeable to water." - This statement is incorrect because the descending limb is actually permeable to water.
- **Statement 3**: "The ascending limb of loop of Henle is impermeable to water." - This statement is correct (same as Statement 1).
- **Statement 4**: "The descending limb of loop of Henle is impermeable to electrolytes." - This statement is incorrect because the descending limb does not allow electrolytes to pass through, but it is not the primary function of this limb.

5. **Conclusion**: Based on the analysis, the correct statements are Statements 1 and 3. Therefore, the correct answer is that the ascending limb of the loop of Henle is impermeable to water.

### Final Answer:
The correct statements are:
- The ascending limb of loop of Henle is impermeable to water (Statement 1).
- The ascending limb of loop of Henle is impermeable to water (Statement 3).