Cortex and medulla region in frog kidney.

Options

A. Less distinct
B. More distinct
C. Absent
D. None

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of Frog Kidneys**:
- Frogs possess two kidneys that are positioned identically on either side of the body.

2. **Kidney Lobulation**:
- The kidneys of frogs are described as trilobular, meaning they are divided into three lobes.

3. **Cortex and Medulla Presence**:
- In frogs, the traditional distinction between the cortex and medulla regions found in other vertebrates is not present. Therefore, we can conclude that these regions are absent.

4. **Loop of Henle**:
- Additionally, frogs do not have a Loop of Henle, which is a structure typically found in the kidneys of mammals and some other vertebrates.

5. **Malpighian Tubules**:
- Instead of having distinct cortical and medullary regions, the kidneys of frogs contain scattered Malpighian tubules, which are involved in excretion.

6. **Excretion Process**:
- The excretory waste in frogs is drained from the coelom (the body cavity) through nephrostomes, which are openings in the kidneys. The waste then exits the body.

7. **Conclusion**:
- Based on the absence of distinct cortex and medulla regions in frog kidneys, the correct answer is that these regions are absent.

### Final Answer:
The cortex and medulla regions in frog kidneys are **absent**.

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