Of the total nephrons, juxtamedullary nephrons constitute.

Options

A. 15 %
B. 45%
C. 65%
D. 85%

Explanation

**Step-by-Step Solution:**

1. **Understanding Nephrons**: Nephrons are the functional units of the kidney, responsible for filtering blood and forming urine. There are two main types of nephrons: cortical nephrons and juxtamedullary nephrons.

2. **Identifying Juxtamedullary Nephrons**: Juxtamedullary nephrons are characterized by their long loops of Henle that extend deep into the medulla of the kidney. They play a crucial role in concentrating urine and regulating water balance.

3. **Percentage Composition**: The question asks for the percentage of juxtamedullary nephrons out of the total number of nephrons in the kidney.

4. **Known Facts**: It is established that juxtamedullary nephrons constitute about 15% of the total nephrons in the human kidney.

5. **Conclusion**: Therefore, the answer to the question is that juxtamedullary nephrons constitute **15%** of the total nephrons.

---