For the occurrence of inspiration intra pulmonary pressure should be

Options

A. equal to atmospheric pressure
B. more than atmospheric pressure
C. less than atmospheric pressure
D. all of these

Answer

To solve the question regarding the conditions required for inspiration, we need to understand the mechanics of breathing and the relationship between intrapulmonary pressure and atmospheric pressure.

### Step-by-Step Solution:

1. **Understanding Inspiration**:
- Inspiration is the process of taking air into the lungs. It occurs when the diaphragm contracts and the thoracic cavity expands.

2. **Role of the Diaphragm**:
- During inspiration, the diaphragm contracts, which increases the volume of the thoracic cavity. This increase in volume leads to a decrease in the pressure within the thoracic cavity.

3. **Intrapulmonary Pressure**:
- The pressure within the lungs is referred to as intrapulmonary pressure (or intra-alveolar pressure). For air to flow into the lungs, the intrapulmonary pressure must be lower than the atmospheric pressure.

4. **Pressure Comparison**:
- When the diaphragm contracts and the volume of the thoracic cavity increases, the intrapulmonary pressure decreases. This decrease in pressure creates a pressure gradient that allows air to flow into the lungs from the outside atmosphere.

5. **Conclusion**:
- Therefore, for inspiration to occur, the intrapulmonary pressure must be **less than atmospheric pressure**. This is necessary for air to move into the lungs.

6. **Correct Answer**:
- The correct option is **C: less than atmospheric pressure**.