Question

bio - 202 topic 4: respiratory system physiology
practice it
what happens to air pressure in the lungs during exhalation?
the volume of the chest cavity increases, which decreases the air pressure in the lungs.
the volume of the chest cavity stays the same, which maintains the air pressure in the lungs.
the air pressure in the lungs decreases as a result of increased oxygen intake.
the air pressure in the lungs increases due to the movement of the diaphragm.
the volume of the chest cavity decreases, which increases the air pressure in the lungs.

Explanation:

During exhalation, the diaphragm relaxes and moves upward, while the intercostal muscles relax, causing the ribcage to move downward and inward. This reduces the volume of the chest cavity. According to Boyle's Law (\(P_1V_1 = P_2V_2\), where pressure \(P\) and volume \(V\) are inversely related at a constant temperature), a decrease in volume (\(V\)) leads to an increase in pressure (\(P\)) in the lungs. So, the air pressure in the lungs increases relative to the atmospheric pressure, and air is forced out of the lungs.

• The first option describes inhalation (volume increases, pressure decreases).
• The second option is incorrect as volume changes during exhalation.
• The third option is wrong because exhalation is not directly about oxygen intake (that's inhalation - related in terms of gas exchange).
• The fourth option is incorrect as it's the volume - pressure relationship (not just diaphragm movement in isolation) that's key here.

Answer:

The volume of the chest cavity decreases, which increases the air pressure in the lungs.