In which part of nephron, the glomerular filtrate become hypotonic ?

Options

A. PCT
B. Descending limb of loop of Henle
C. Ascending limb of loop of Henle
D. Both (1) and (2)

Answer

To determine in which part of the nephron the glomerular filtrate becomes hypotonic, we can analyze the functions of different segments of the nephron.

### Step-by-Step Solution:

1. **Understanding Hypotonic Filtrate**:
- A hypotonic solution has a lower concentration of solutes compared to the solvent (water). This means that in a hypotonic filtrate, there is more water and fewer solutes.

2. **Identifying Nephron Parts**:
- The nephron consists of several parts:
- Proximal Convoluted Tubule (PCT)
- Loop of Henle (which has a descending limb and an ascending limb)
- Distal Convoluted Tubule (DCT)
- Collecting Duct

3. **Analyzing the Proximal Convoluted Tubule (PCT)**:
- In the PCT, about 70-80% of electrolytes and water are reabsorbed. The filtrate remains isotonic because both solutes and water are reabsorbed proportionally.

4. **Analyzing the Loop of Henle**:
- **Descending Limb**: This part is permeable to water but not to solutes. As water is reabsorbed here, the concentration of solutes in the filtrate increases, making it hypertonic.
- **Ascending Limb**: This part is impermeable to water but allows for the reabsorption of solutes (like sodium and chloride). As solutes are reabsorbed without water, the concentration of solutes decreases, leading to a hypotonic filtrate.

5. **Analyzing the Distal Convoluted Tubule (DCT) and Collecting Duct**:
- In the DCT, further reabsorption of solutes occurs, but water reabsorption is regulated by hormones (like aldosterone). The filtrate can still be hypotonic depending on the body's needs.
- In the Collecting Duct, water reabsorption can occur based on the body's hydration status, influenced by antidiuretic hormone (ADH). The filtrate can become concentrated or dilute here.

6. **Conclusion**:
- The part of the nephron where the glomerular filtrate becomes hypotonic is the **ascending limb of the Loop of Henle**.

### Final Answer:
The glomerular filtrate becomes hypotonic in the **ascending limb of the Loop of Henle**.

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