Vasa recta is absent in --------------

Answer

**Step-by-Step Solution:**

1. **Understanding Vasa Recta**: Vasa recta are specialized blood vessels that supply blood to the nephron, particularly the loop of Henle. They play a crucial role in the concentration of urine.

2. **Identifying Nephron Types**: There are two main types of nephrons in the kidney:
- **Cortical Nephrons**: These make up about 85% of the total nephrons. They have a short loop of Henle that does not extend deep into the medulla.
- **Juxtamedullary Nephrons**: These constitute about 15% of the nephrons and have a long loop of Henle that extends deep into the medulla.

3. **Location of Vasa Recta**: The vasa recta are primarily associated with the juxtamedullary nephrons due to their long loops of Henle, which require a specialized blood supply for efficient function.

4. **Conclusion**: Since cortical nephrons have a short loop of Henle and do not extend into the medulla, the vasa recta is either absent or highly reduced in these nephrons.

5. **Final Answer**: Therefore, the vasa recta is absent in **cortical nephrons**.

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