Statement-1: The final reabsorption of water from the urine into the blood occurs through the collecting duct of a mammalian nephron resulting in thhe production of hyperosmotic urine.
Statement-2: The loop of henle creates a sodium gradient in the interstitial fluid.

Options

A. both statements 1 and 2 are correct.
B. Statement 1 is correct but statement 2 is incorrect
C. Statement 1 is incorrect but statement 2 is correct
D. Both statements 1 and 2 are incorrect.

Explanation

### Step-by-Step Solution:

1. **Understanding Statement 1**:
- The statement claims that the final reabsorption of water from urine into the blood occurs through the collecting duct of a mammalian nephron, resulting in the production of hyperosmotic urine.
- In the nephron, the collecting duct is responsible for the reabsorption of water. When water is reabsorbed, the concentration of solutes in the urine increases, leading to hyperosmotic urine (urine with higher osmolarity than blood).

2. **Understanding Statement 2**:
- This statement indicates that the loop of Henle creates a sodium gradient in the interstitial fluid.
- The loop of Henle plays a crucial role in establishing a concentration gradient in the renal medulla. It utilizes a counter-current mechanism to increase osmolarity in the interstitial fluid, primarily through the reabsorption of sodium (Na+) and chloride (Cl-) ions, as well as urea.

3. **Analyzing the Relationship Between the Two Statements**:
- Both statements are interconnected. The loop of Henle creates a sodium gradient that allows for the reabsorption of water in the collecting duct. This process results in the production of hyperosmotic urine.
- Therefore, both statements are correct.

4. **Conclusion**:
- The final conclusion is that both Statement 1 and Statement 2 are correct. The collecting duct reabsorbs water to produce hyperosmotic urine, and the loop of Henle establishes the sodium gradient necessary for this process.