In a glomerulus,

Options

A. afferent arteriole has wider lumen than efferent arteriole
B. afferent arteriole has narrower lumen than efferent arteriole
C. afferent capillaries are thicker than efferent capillaries
D. afferent capillaries are thinner than efferent capillaries

Answer

**Step-by-Step Solution:**

1. **Understanding the Glomerulus**: The glomerulus is a network of capillaries located within the Bowman's capsule in the kidney. It plays a crucial role in the filtration of blood.

2. **Identifying the Arterioles**: There are two types of arterioles associated with the glomerulus:
- **Afferent Arteriole**: This is the vessel that brings blood into the glomerulus.
- **Efferent Arteriole**: This is the vessel that carries blood away from the glomerulus.

3. **Analyzing the Lumen Size**:
- The afferent arteriole has a wider lumen compared to the efferent arteriole. This difference in size is important because it allows for high-pressure blood flow into the glomerulus, facilitating the filtration process.

4. **Evaluating the Options**:
- **Option A**: Efferent arteriole has a wider lumen than afferent arteriole. (Correct)
- **Option B**: Efferent arteriole has a narrower lumen than afferent arteriole. (Incorrect)
- **Option C**: Efferent capillaries are thicker than efferent capillaries. (Incorrect, as the term "efferent capillaries" is a misnomer; it should refer to arterioles)
- **Option D**: Efferent capillaries are thinner than efferent capillaries. (Incorrect, same reason as above)

5. **Conclusion**: Based on the analysis, the correct answer is **Option A**: "Efferent arteriole has a wider lumen than afferent arteriole."

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