Study the statement given below and answer the question " Even though the contents of stomach are very acidic, the stomach usually does not cause damage to itself ".
Identify this reasons (I to iv) given below which are responsible for the above statement.
(i)The release of gastric juices is controlled to avoid too high a concentration.
(ii)The stomach lining is quick to repair itself
(iii)Mucus forms a thick protective coating for the stomach
(iv)Food and water dilute the gastric juices .

Options

A. (i),(ii) and (iii)
B. (ii),(iii) and (iv)
C. (i) and (iv) only
D. All of the above

Answer

To address the question regarding why the stomach does not damage itself despite its highly acidic contents, we will analyze each of the provided reasons (i to iv) and determine their validity.

### Step-by-Step Solution:

1. **Understanding the Stomach's Environment:**
- The stomach contains gastric juices, which are highly acidic (pH 2-3) due to the presence of hydrochloric acid (HCl) secreted by parietal cells. This acidity is essential for digestion but poses a risk of damaging the stomach lining.

2. **Evaluating Each Reason:**
- **(i) The release of gastric juices is controlled to avoid too high a concentration.**
- This statement is misleading. While the release of gastric juices is regulated, it does not directly prevent damage to the stomach lining. The primary function of gastric juices is to aid in digestion, not to protect the stomach from acidity.
- **Conclusion:** This reason is **not responsible** for preventing stomach damage.

- **(ii) The stomach lining is quick to repair itself.**
- While the stomach lining does have some regenerative capabilities, this statement is not the primary reason for the stomach's protection against its own acid. The focus should be on prevention rather than repair.
- **Conclusion:** This reason is **not responsible** for preventing stomach damage.

- **(iii) Mucus forms a thick protective coating for the stomach.**
- This is a crucial point. Goblet cells in the stomach secrete mucus, which forms a protective barrier that prevents the acidic gastric juices from damaging the stomach lining. This mucus layer is vital for protecting the stomach wall from the corrosive effects of HCl.
- **Conclusion:** This reason is **responsible** for preventing stomach damage.

- **(iv) Food and water dilute the gastric juices.**
- While food and water do dilute gastric juices, this dilution is not the primary mechanism that protects the stomach lining. The protective mucus layer is far more significant in preventing damage.
- **Conclusion:** This reason is **not primarily responsible** for preventing stomach damage.

3. **Final Answer:**
- The correct reason that explains why the stomach does not damage itself despite its acidic contents is **(iii) Mucus forms a thick protective coating for the stomach.**