Which of the following statement is not ture ?

Options

A. Descending limb of loop of henle is permeable to urea
B. DCT function in `K^(+),Na^(+)` homeostasis
C. Descending limb is impermeable to water
D. Loop of Henle is largely resopnsible for concentrating urine

Answer

To determine which statement is not true regarding the loop of Henle and its functions, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Loop of Henle**:
- The loop of Henle consists of two main parts: the descending limb and the ascending limb. Each limb has distinct permeability characteristics.

2. **Analyzing the First Statement**:
- **Statement**: "Descending limb of loop of Henle is permeable to urea."
- **Analysis**: The descending limb is primarily permeable to water and has very low permeability to urea. Therefore, this statement is true.

3. **Analyzing the Second Statement**:
- **Statement**: "DCT functions in sodium, potassium, and sodium homeostasis."
- **Analysis**: The Distal Convoluted Tubule (DCT) plays a significant role in the reabsorption of sodium and potassium, thus maintaining ionic homeostasis. This statement is also true.

4. **Analyzing the Third Statement**:
- **Statement**: "Descending limb is impermeable to water."
- **Analysis**: This statement is incorrect. The descending limb of the loop of Henle is permeable to water, allowing water to be reabsorbed into the surrounding medullary interstitium. Therefore, this statement is false.

5. **Analyzing the Fourth Statement**:
- **Statement**: "Loop of Henle is largely responsible for concentrating urine."
- **Analysis**: The loop of Henle, along with the Vasa Recta, is indeed crucial for the countercurrent mechanism that concentrates urine. This statement is true.

6. **Conclusion**:
- After analyzing all the statements, the statement that is not true is the third one: "Descending limb is impermeable to water."

### Final Answer:
The statement that is not true is: **"Descending limb is impermeable to water."**