When we breathe in, expansion of the ribcage allows movement of oxygen into the lungs due to?

When we breathe in, the expansion of the ribcage creates a decrease in pressure within the chest cavity compared to the outside air pressure. This difference in pressure allows air, which naturally moves from areas of high pressure to areas of low pressure, to flow into the lungs. This process is known as inhalation. The oxygen in the inhaled air then passes into the bloodstream through tiny air sacs called alveoli.