Which part of nephron is impermeable to water

Options

A. distal tubule
B. collecting duct
C. proximal tubule
D. ascending limb of Henle's loop

Answer

To determine which part of the nephron is impermeable to water, we can analyze the structure and function of each part of the nephron. Here’s a step-by-step breakdown:

### Step 1: Understand the Structure of the Nephron
The nephron is the functional unit of the kidney and consists of several parts, including:
- Proximal Convoluted Tubule (PCT)
- Loop of Henle (which has a descending limb and an ascending limb)
- Distal Convoluted Tubule (DCT)
- Collecting Duct

### Step 2: Analyze Each Part of the Nephron
1. **Proximal Convoluted Tubule (PCT)**: This part is highly permeable to water and is responsible for the reabsorption of a significant amount of water, glucose, amino acids, and ions.

2. **Loop of Henle**:
- **Descending Limb**: This part is permeable to water, allowing for water reabsorption.
- **Ascending Limb**: This part is impermeable to water but permeable to ions, particularly sodium and chloride ions.

3. **Distal Convoluted Tubule (DCT)**: This part has conditional permeability to water, which is regulated by hormones like antidiuretic hormone (ADH).

4. **Collecting Duct**: This part is also permeable to water, especially under the influence of ADH.

### Step 3: Identify the Answer
From the analysis, the part of the nephron that is specifically impermeable to water is the **ascending limb of the Loop of Henle**.

### Conclusion
Thus, the correct answer to the question "Which part of nephron is impermeable to water?" is **the ascending limb of Henle's loop**.

---