The dotted appearance of cortex of kidney is due to

Options

A. ducts of Bellini
B. convoluted parts
C. loop of Henle
D. collecting tubes.

Explanation

### Step-by-Step Solution:

1. **Understanding the Structure of the Kidney**: The kidney is made up of several parts, including the cortex, medulla, and pelvis. The cortex is the outer region of the kidney.

2. **Identifying the Appearance of the Cortex**: The cortex of the kidney has a unique appearance characterized by small, dotted structures. This appearance is crucial for understanding kidney function.

3. **Recognizing the Components of the Cortex**: The dotted appearance is primarily due to the presence of specific structures within the cortex. These structures are the proximal convoluted tubules (PCT) and distal convoluted tubules (DCT).

4. **Explaining the Role of Convoluted Tubules**: The proximal convoluted tubule is responsible for the reabsorption of water, ions, and nutrients, while the distal convoluted tubule plays a role in the regulation of potassium, sodium, and pH. The convoluted nature of these tubules contributes to the dotted appearance.

5. **Evaluating the Options**:
- Option 1: Trachs of Bellini - Incorrect, as these are part of the collecting ducts located in the medulla.
- Option 2: Convoluted parts - Correct, as this refers to the proximal and distal convoluted tubules.
- Option 3: Loops of Henle - Incorrect, as these are located in the medulla and do not contribute to the cortex's appearance.
- Option 4: Collecting ducts - Incorrect, as they are also located in the medulla and do not contribute to the dotted appearance of the cortex.

6. **Conclusion**: The dotted appearance of the cortex of the kidney is due to the convoluted parts, specifically the proximal and distal convoluted tubules. Therefore, the correct answer is option number 2.