The method by which Oxygen-rich Gas is inhaled and Carbon Dioxide is expelled is known as breathing mechanism. The Diaphragm slides down and the ribs rise up and outwards during Inspiration. This movement expands the area in our chest cavity, allowing more air to enter the lungs.
The diaphragm flattens and slides lower, while the intercostal muscles lift and expand the rib cage. Inspiration : As the thorax expands, the internal air pressure lowers, therefore air from the outside rushes into the lungs (at a greater pressure than within the thorax) to equalise the pressures.