Which one is not the function of kidney

Options

A. Osmoregulation
B. Salt retention
C. Excretion
D. Synthesis of urea

Answer

To determine which option is not a function of the kidney, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Kidney Functions**:
- The kidneys are vital organs responsible for various functions, primarily related to the excretion of waste products and the regulation of bodily fluids.

2. **Analyzing the Options**:
- **Option A: Osmoregulation**:
- The kidneys play a crucial role in osmoregulation, which is the regulation of water and electrolyte balance in the body. They filter blood and help maintain the osmotic balance by adjusting the concentration of urine.
- **Conclusion**: This is a function of the kidney.

- **Option B: Salt Retention**:
- During the filtration process, the kidneys reabsorb essential salts and ions, which helps in maintaining electrolyte balance and contributes to osmoregulation.
- **Conclusion**: This is also a function of the kidney.

- **Option C: Excretion**:
- The primary function of the kidneys is excretion. They remove metabolic waste products, including nitrogenous wastes, from the blood and excrete them in urine.
- **Conclusion**: This is a fundamental function of the kidney.

- **Option D: Synthesis of Urea**:
- Urea is a nitrogenous waste product formed in the liver through the urea cycle. The kidneys do not synthesize urea; they only excrete it after it has been produced in the liver.
- **Conclusion**: This is NOT a function of the kidney.

3. **Final Answer**:
- The option that is not a function of the kidney is **D: Synthesis of Urea**.