Vasa recta refers to

Options

A. Rectum region of insects
B. Blood capillaries in invertebrates
C. A fine blood capillary network of afferent artriole
D. A fine capillary network which runs parallel to Henle's loop

Answer

### Step-by-Step Solution:

1. **Understanding the Nephron Structure**:
- The nephron is the structural and functional unit of the kidney. It consists of various parts including the Bowman's capsule, glomerulus, proximal convoluted tubule (PCT), loop of Henle, and distal convoluted tubule (DCT).

2. **Identifying the Loop of Henle**:
- The loop of Henle is a U-shaped structure that consists of a descending limb and an ascending limb. It plays a crucial role in the concentration of urine.

3. **Recognizing the Vasa Recta**:
- The vasa recta refers to the network of blood vessels that surround the loop of Henle. This network consists of capillaries that run parallel to the loop of Henle.

4. **Analyzing the Options**:
- Option 1: Rectum region of insects - Incorrect.
- Option 2: Blood capillaries in invertebrates - Incorrect.
- Option 3: Fine blood capillary network of afferent arteriole - Incorrect, as this refers to the glomerulus.
- Option 4: Fine capillary network which runs parallel to the Henle's loop - Correct.

5. **Conclusion**:
- The correct answer is option 4: "Fine capillary network which runs parallel to the Henle's loop." The vasa recta is essential for the reabsorption of water and electrolytes, aiding in osmoregulation.