The pathway of oxygen and the exchanging of gases take place in the respiratory system. As we take in air(oxygen), it goes inside our nose where the cilia trap the dust in the air we breathe. The air passes through the pharynx, larynx, trachea, then the lungs where it passes through the bronchus, bronchioles, then lastly the alveoli where oxygen is being exchanged by carbon dioxide inside our body to be expelled or exhaled.