The narrow apex of pyramid is called

Options

A. Column of Bertin
B. Calyx
C. Papillary duct of Bellini
D. Pelvis

Answer

### Step-by-Step Solution:

1. **Understanding the Structure**: The question asks about the narrow apex of a pyramid in the context of kidney anatomy. In the kidney, the pyramids are structures found in the renal medulla.

2. **Identifying the Options**: The options given are:
- Column of Burton
- Calyx
- Papillary duct of Bellini
- Pelvis

3. **Analyzing the Options**:
- **Column of Burton**: This is not related to the pyramids of the kidney.
- **Calyx**: This refers to the cup-like structures that collect urine from the renal pyramids but does not specifically refer to the apex.
- **Papillary duct of Bellini**: This is the duct that is located at the apex of the renal pyramids and is responsible for transporting urine to the calyces.
- **Pelvis**: This refers to the funnel-shaped structure that collects urine from the calyces but is not the apex of the pyramid.

4. **Conclusion**: Based on the analysis, the structure that corresponds to the narrow apex of the renal pyramid is the **papillary duct of Bellini**.

5. **Final Answer**: The narrow apex of the pyramid is called the **papillary duct of Bellini**.