Mucus is secreted by the `:-`

Options

A. Stomach
B. Duodenum
C. Large intestine
D. All of the above

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks where mucus is secreted in the human body. The options provided are the stomach, duodenum, and large intestine.

2. **Mucus in the Stomach**:
- The stomach contains specialized cells known as goblet cells.
- These goblet cells secrete mucus to protect the stomach lining from the highly acidic environment (pH due to gastric acid).
- The mucus acts as a barrier, preventing damage to the stomach walls.

3. **Mucus in the Duodenum**:
- The duodenum is the first part of the small intestine and has an alkaline pH.
- Mucus is also secreted here to protect the intestinal lining from the alkaline environment and to facilitate the movement of food.
- It helps in lubricating the food as it passes through the digestive tract.

4. **Mucus in the Large Intestine**:
- The large intestine also contains goblet cells that secrete mucus.
- The primary function of mucus in the large intestine is to lubricate undigested food material.
- This lubrication is essential for the smooth passage of waste through the intestines, especially as water is absorbed.

5. **Conclusion**: Mucus is secreted by goblet cells present in the stomach, duodenum, and large intestine. Therefore, the answer to the question is that mucus is secreted by all of these parts.