How does air enter the lungs during inhalation?

Air enters the lungs during inhalation primarily due to the change in pressure created by the mechanics of breathing. Specifically, when the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. According to Boyle's Law, when the volume of a container increases, the pressure within that container decreases. This decrease in lung pressure creates a pressure gradient between the atmosphere and the lungs. Air naturally flows from an area of higher pressure (the atmosphere) to an area of lower pressure (the lungs) through the respiratory tract.

Thus, when lung pressure is less than atmospheric pressure, air will flow into the lungs, facilitating inhalation. This is a key aspect of respiratory physiology that underscores the importance of diaphragm contraction and thoracic volume changes in effective breathing.