Question

multiple choice question
why does air flow into the lungs during inspiration?
o because intra - alveolar pressure is greater than atmospheric pressure, and air flows from low to high pressure
o because the intra - alveolar pressure is the same as the atmosphere pressure
o because intra - alveolar pressure is less than atmospheric pressure, and air flows from high to low pressure

Explanation:

During inspiration, the diaphragm and intercostal muscles contract, increasing the volume of the thoracic cavity. According to Boyle's law ($P_1V_1 = P_2V_2$, where pressure and volume are inversely related), an increase in volume leads to a decrease in intra - alveolar pressure. Air flows from an area of higher pressure (atmospheric pressure) to an area of lower pressure (intra - alveolar pressure).

• The first option is incorrect because air flows from high to low pressure, not low to high.
• The second option is incorrect. If intra - alveolar pressure is the same as atmospheric pressure, there will be no net flow of air.

Answer:

because intra - alveolar pressure is less than atmospheric pressure, and air flows from high to low pressure