Concentration of urine depends upon

Options

A. Length of PCT
B. Length of loop of Henle
C. Length of DCT
D. Both (2) and (3)

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks about the factors that influence the concentration of urine.

2. **Analyzing the Options:**
- **Option 1: Length of PCT (Proximal Convoluted Tubule)**
- The PCT is primarily involved in the reabsorption of nutrients, water, and ions. It does not significantly influence urine concentration.

- **Option 2: Length of Loop of Henle**
- The Loop of Henle plays a crucial role in concentrating urine. It has a hairpin structure with a thin descending limb that is permeable to water and a thick ascending limb that is impermeable to water. The longer the Loop of Henle, the more concentrated the urine can become due to the countercurrent multiplication mechanism.

- **Option 3: Length of Distal Convoluted Tubule**
- The DCT is involved in the reabsorption of sodium and the secretion of potassium but does not significantly affect the concentration of urine.

- **Option 4: Both Second and Third**
- Since the DCT does not contribute to urine concentration, this option is incorrect.

3. **Conclusion:**
Based on the analysis, the concentration of urine primarily depends on the length of the Loop of Henle. Therefore, the correct answer is **Option 2: Length of Loop of Henle**.

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