Expiration occurs when

Options

A. Intrapulmonary pressure `gt` Atmospheric pressure
B. Intrapulmonary pressure `lt ` Atmospheric pressure
C. Intrapulmonary pressure = Atmospheric pressure
D. Intrapulmonary pressure `gt`= Atmospheric pressure

Answer

**Step-by-Step Solution:**

1. **Understanding Expiration**: Expiration, also known as exhalation, is the process of breathing out air from the lungs. This occurs after inhalation, where air is drawn into the lungs.

2. **Pressure Gradient Concept**: The movement of air during breathing is driven by differences in pressure, known as pressure gradients. This involves the relationship between the pressure inside the lungs (intrapulmonary pressure) and the pressure outside in the atmosphere (atmospheric pressure).

3. **Intrapulmonary Pressure During Inhalation**: When we inhale, the intrapulmonary pressure is lower than the atmospheric pressure. This difference allows air to flow into the lungs.

4. **Intrapulmonary Pressure During Expiration**: Conversely, during expiration, the intrapulmonary pressure becomes greater than the atmospheric pressure. This pressure difference causes air to flow out of the lungs.

5. **Conclusion**: Therefore, expiration occurs when the intrapulmonary pressure is greater than the atmospheric pressure.

**Final Answer**: Expiration occurs when the intrapulmonary pressure is greater than the atmospheric pressure.

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