Read the following statements and find out the INCORRECT statement .
(a) During urine formation, the tubular cells secrete substance like `H^+, Na^+ and HCO_3^-` into the filtrate.
(b) As glomerular filtrate move down in descending limb of Henle it gets concentrated and as concentrated filtrate pass upward in ascending limb of HL it gets diluted.
(c) Conditional reabsorption of `Na^+` and water takes place in PCT.
(d) Reabsorption in ascending limb of HL is minimum.

Options

A. a and b
B. b and c
C. c and d
D. a and c

Answer

To solve the question, we need to analyze each statement provided and identify which one is incorrect. Let's go through them step by step.

### Step 1: Analyze Statement (a)
**Statement (a)**: During urine formation, the tubular cells secrete substances like `H^+, Na^+ and HCO_3^-` into the filtrate.

- **Analysis**: In the process of urine formation, tubular cells in the nephron do secrete hydrogen ions (`H^+`) and ammonia, but they primarily reabsorb bicarbonate ions (`HCO_3^-`). Sodium ions (`Na^+`) are typically reabsorbed rather than secreted. Therefore, this statement is incorrect.

### Step 2: Analyze Statement (b)
**Statement (b)**: As glomerular filtrate moves down in the descending limb of Henle, it gets concentrated, and as concentrated filtrate passes upward in the ascending limb of Henle, it gets diluted.

- **Analysis**: The descending limb of the loop of Henle is permeable to water, allowing water to exit and thus concentrating the filtrate. Conversely, the ascending limb is impermeable to water but allows the reabsorption of electrolytes, which dilutes the filtrate. This statement is correct.

### Step 3: Analyze Statement (c)
**Statement (c)**: Conditional reabsorption of `Na^+` and water takes place in PCT.

- **Analysis**: The proximal convoluted tubule (PCT) is responsible for the reabsorption of a significant amount of sodium ions and water. However, the statement suggests that this reabsorption is conditional, which may imply variability that is not typically the case. The PCT consistently reabsorbs a large percentage of sodium and water. This statement is misleading and can be considered incorrect.

### Step 4: Analyze Statement (d)
**Statement (d)**: Reabsorption in the ascending limb of Henle is minimum.

- **Analysis**: The ascending limb of the loop of Henle does have a lower reabsorption rate compared to the PCT, but it is still significant for the reabsorption of sodium and chloride ions. However, it is true that the reabsorption is less compared to the descending limb. This statement is generally considered correct.

### Conclusion
The incorrect statements are (a) and (c). Therefore, the answer to the question is that statements (a) and (c) are incorrect.