Question

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what happens to air pressure in the lungs during inhalation?
the air pressure in the lungs remains the same during inhalation.
inhalation has no effect on air pressure in the lungs.
the volume of the chest cavity decreases, which increases the air pressure in the lungs.
the volume of the chest cavity stays the same during inhalation, which has no effect on the air pressure in the lungs.
the volume of the chest cavity increases, which decreases the air pressure in the lungs.

Explanation:

During inhalation, the diaphragm contracts and moves downward, and the intercostal muscles contract, causing the rib - cage to expand. This increases the volume of the chest cavity. According to Boyle's Law ($P_1V_1 = P_2V_2$, when temperature is constant), when the volume ($V$) of a gas - containing space (the lungs in this case) increases, the pressure ($P$) decreases. So, an increase in chest cavity volume leads to a decrease in air pressure in the lungs, which allows air to flow in from the outside (where the pressure is higher).

Answer:

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