Brush border is characteristic of

Options

A. proximal convoluted tubule
B. Bowman's capsule
C. Glomerulus
D. all of the above

Answer

### Step-by-Step Solution

1. **Understanding the Question**: The question asks about the characteristic feature known as "brush border" and which structure it is associated with in the excretory system.

2. **Identifying the Options**:
- Option A: Proximal Convoluted Tubule (PCT)
- Option B: Bowman's Capsule
- Option C: Glomerulus
- Option D: All of the above

3. **Analyzing Each Option**:
- **Proximal Convoluted Tubule (PCT)**: The PCT is known to have a brush border made up of microvilli. This structure increases the surface area for reabsorption of water, electrolytes, and nutrients. It is highly active in reabsorption, accounting for about 70-80% of electrolyte reabsorption.
- **Bowman's Capsule**: This structure is involved in the filtration of blood to form urine but does not possess a brush border. Its primary function is ultrafiltration.
- **Glomerulus**: Similar to Bowman's Capsule, the glomerulus is also involved in the filtration process and does not have a brush border.
- **All of the Above**: Since only the PCT has a brush border, this option cannot be correct.

4. **Conclusion**: The brush border is a characteristic feature of the Proximal Convoluted Tubule (PCT). Therefore, the correct answer is Option A: Proximal Convoluted Tubule.

### Final Answer
**The brush border is characteristic of the Proximal Convoluted Tubule (PCT).**

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