Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What happens to the pressure in the lungs during expiration?

1. It decreases

2. It remains constant

3. It increases

4. It fluctuates

The correct answer is: It increases

During expiration, the diaphragm and intercostal muscles relax, causing the thoracic cavity to decrease in volume. This decrease in volume leads to an increase in pressure within the lungs relative to the atmospheric pressure outside. Specifically, as the volume of the lungs decreases, the air inside is compressed, resulting in higher pressure. Consequently, air is expelled from the lungs into the atmosphere until the pressures equalize. This physiological process is governed by Boyle's Law, which states that the pressure of a gas is inversely related to its volume when the temperature is held constant. Thus, during expiration, as the lung volume decreases, the pressure increases, allowing air to flow out of the lungs effectively.