When we breathe we draw air in through the nose and mouth and into the lungs. Air travels down a tube called the trachea that forks into other tubes called bronchi, which lead into the lungs. From her the air passed into the lungs.
From here the air passes into a series of smaller air passages and eventually into tiny air sacs, or bladders, called alveoli. Oxygen is absorbed through the thin walls of the alveoli. Oxygen is absorbed through the thin walls of the alveoli into the blood and carbon dioxide is released to be breathed out as a waste product.