Read the following statements and select the correct option
Statement 1 : When the urine moves through the descending limb, it becomes hypertonic to blood plasma and as it passes through the ascending limb of Henl's loop it becomes hypotonic to blood plasma
Statement 2 : The decending limb is permeable to sodium ions, while the ascending limb is impermeable to sodium ions

Options

A. Statement `a` is correct and `b` is wrong
B. Statement `a` is wrong and `b` is correct
C. Both statement `a` and `b` are wrong
D. Both statement `a` and `b` are correct

Answer

To solve the question, we need to analyze both statements regarding the function of the loop of Henle in the nephron of the kidney.

### Step-by-Step Solution:

1. **Understanding Statement 1**:
- The statement claims that when urine moves through the descending limb of the loop of Henle, it becomes hypertonic to blood plasma.
- As it moves through the ascending limb, it becomes hypotonic to blood plasma.
- **Analysis**: The descending limb is indeed permeable to water, allowing water to exit, which concentrates the urine and makes it hypertonic compared to blood plasma. As the urine moves up the ascending limb, it is impermeable to water but allows sodium and other ions to be reabsorbed, thus diluting the urine and making it hypotonic to blood plasma.
- **Conclusion**: Statement 1 is correct.

2. **Understanding Statement 2**:
- The statement claims that the descending limb is permeable to sodium ions, while the ascending limb is impermeable to sodium ions.
- **Analysis**: This is incorrect. The descending limb is primarily permeable to water and not to sodium ions. In contrast, the ascending limb is impermeable to water but actively transports sodium ions out of the urine, making it possible for the urine to become hypotonic.
- **Conclusion**: Statement 2 is incorrect.

3. **Final Evaluation**:
- Based on the analysis, Statement 1 is correct, and Statement 2 is incorrect. Therefore, the correct option is that Statement A is correct, and Statement B is incorrect.

### Final Answer:
- **Correct Option**: Statement A is correct, Statement B is incorrect.