Which of the following is the characteristic of a metanephric kidney

Options

A. Hypotonic urine production
B. Excess secretion of uric acid
C. Loop of Henle
D. Hormone production

Answer

### Step-by-Step Solution

1. **Understanding Metanephric Kidney**:
- The metanephric kidney is the most advanced form of kidney found in mammals. It is characterized by its complex structure and functionality.

2. **Identifying the Components of the Nephron**:
- The nephron, which is the functional unit of the metanephric kidney, consists of several parts:
- Glomerular apparatus
- Proximal Convoluted Tubule (PCT)
- Loop of Henle
- Distal Convoluted Tubule (DCT)

3. **Function of the Loop of Henle**:
- The Loop of Henle plays a crucial role in the concentration of urine by facilitating the reabsorption of water and salts, which is essential for maintaining body fluid balance.

4. **Analyzing the Options**:
- **Hypotonic Urine Production**: This is not a characteristic of metanephric kidneys as they can produce concentrated urine.
- **Excess Secretion of Uric Acid**: This is more characteristic of organisms that excrete uric acid, such as birds and reptiles, not mammals with metanephric kidneys.
- **Loop of Henle**: This is a defining feature of the metanephric kidney, as it is involved in the reabsorption processes.
- **Hormone Production**: While kidneys do play a role in hormone production (like erythropoietin), this is not a defining characteristic of the metanephric kidney itself.

5. **Conclusion**:
- The correct answer is the **Loop of Henle**, as it is a key structural and functional component of the metanephric kidney.

### Final Answer
The characteristic of a metanephric kidney is the **Loop of Henle**.

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