By inhaling we are pumping air through our windpipe into our lungs.
About 300 million air cells in our lungs will filter this air. Only 1/5th of the total amount of air we inhaled contains oxygen. Through a process called heamoglobin the oxygen will be transfered into the blood. Red blood cells are transporting the blood to the heart where it disperses further more in all of our muscles and body tissue. At the same time there is a reverse process that, instead of taking in oxygen, is depositing carbon dioxide (co2).
By inhaling air comes into our body through mouth or nose. Muscle fibres will contract which flattens and presses down our midriff or thoracic diaphragm. Lungs then will be filled with air and expand.
By exhaling these muscles fibres will release tension and the midriff will come up again while air escapes from our lungs out off our body through our mouth or nose.