Following processes will occur if pressure within the pulmonary cavity is lower than the atmospheric pressure?

Options

A. Inhalation of air
B. Expulsion of air
C. No inhalation and expulsion of air occurs
D. Lungs inflate and rupture

Answer

To answer the question about the processes that occur when the pressure within the pulmonary cavity is lower than the atmospheric pressure, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Pulmonary Pressure**: The pulmonary cavity (lungs) is an airtight chamber. The pressure inside the pulmonary cavity can change based on the volume of air in the lungs.

2. **Pressure Comparison**: When the pressure inside the pulmonary cavity is lower than the atmospheric pressure, it indicates that the air pressure outside the lungs is greater than the pressure inside the lungs.

3. **Air Movement**: According to the principles of gas exchange, air moves from an area of higher pressure to an area of lower pressure. Therefore, if the pressure in the pulmonary cavity is lower, air will flow into the lungs from the outside environment.

4. **Inhalation Process**: This influx of air into the lungs is known as inhalation. During inhalation, the diaphragm contracts and the thoracic cavity expands, leading to an increase in lung volume and a decrease in pressure within the lungs.

5. **Conclusion**: Thus, if the pressure within the pulmonary cavity is lower than the atmospheric pressure, the primary process that occurs is the inhalation of air into the lungs.

### Final Answer:
If the pressure within the pulmonary cavity is lower than the atmospheric pressure, the process that occurs is **inhalation of air**.

---