Select the incorrect statement regarding mechanism of urine formation in man.

Options

A. The glomerular filtration rate is about 125 ml per minute.
B. The ultrafiltration is opposed by the colloidal osmotic pressure of plasma.
C. Aldosterone induces greater reabsorption of sodium
D. The counter currect system contributes in diluting the urine.

Explanation

To solve the question regarding the incorrect statement about the mechanism of urine formation in humans, we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Understanding Urine Formation**:
- Urine formation primarily occurs in the nephron, which is the functional unit of the kidney. It involves three main processes: filtration, reabsorption, and secretion.

2. **Analyzing Each Statement**:
- **Statement 1**: "The glomerular filtration rate is about 125 milliliters per minute."
- This statement is correct. The normal glomerular filtration rate (GFR) for a healthy adult is indeed around 125 mL/min.

- **Statement 2**: "Ultrafiltration is opposed by colloidal osmotic pressure of plasma."
- This statement is also correct. The process of ultrafiltration in the glomerulus is indeed opposed by the colloidal osmotic pressure of plasma proteins, which helps regulate the filtration process.

- **Statement 3**: "Aldosterone induces greater reabsorption of sodium."
- This statement is correct as well. Aldosterone is a hormone that promotes sodium reabsorption in the kidneys, which in turn affects blood pressure and fluid balance.

- **Statement 4**: "The counter current system contributes to diluting the urine."
- This statement is incorrect. The counter current mechanism, which involves the loop of Henle and the vasa recta, actually concentrates the urine by allowing for the reabsorption of water and salts, not dilutes it.

3. **Conclusion**:
- The incorrect statement regarding the mechanism of urine formation in man is the fourth statement: "The counter current system contributes to diluting the urine."

### Final Answer:
The incorrect statement is: "The counter current system contributes to diluting the urine."

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