The notch on the centre of inner concave surface of kidney is

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of the Kidney**:
- The kidney is a bean-shaped organ that has an outer concave surface and an inner concave surface.

2. **Identifying the Notch**:
- On the inner concave surface of the kidney, there is a notch that serves as a passageway for various structures.

3. **Naming the Notch**:
- This notch is known as the **hilum**. It is the area where the renal arteries, renal veins, and ureters enter and exit the kidney.

4. **Describing the Surrounding Structures**:
- The outermost part of the kidney is called the **cortex**, while the inner region is referred to as the **medulla**.
- Within the medulla, there are structures known as **medullary pyramids**.
- The cortex extends between these pyramids, forming structures called the **columns of Bertini**.

5. **Conclusion**:
- Therefore, the notch on the center of the inner concave surface of the kidney is called the **hilum**.

### Final Answer:
The notch on the center of the inner concave surface of the kidney is called the **hilum**.

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