What happens to pressure in the lungs when tyou inhale?

When you inhale, the diaphragm and intercostal muscles contract, causing the chest cavity to expand and the lungs to fill with air. This increase in lung volume causes the pressure inside the lungs to decrease relative to the pressure outside the lungs. This pressure difference creates a force that drives air into the lungs.

The decrease in pressure in the lungs during inhalation is essential for bringing air into the lungs. If the pressure inside the lungs were equal to the pressure outside the lungs, there would be no net force to move air into the lungs.