The alveoli trachea bronchi vavuole nucleus( alveoli, trachea, bronchi, vavuole, nucleus ) are tiny air sacs in the lungs surrounded by tiny blood vessels called capillaries. Oxygen Carbon Dioxide Nitrogen Methane Sulfur( Oxygen, Carbon Dioxide, Nitrogen, Methane, Sulfur ) passes from the air sacs into the capillaries where it is taken first to the heart lungs brain liver rings of cartilage( heart, lungs, brain, liver, rings of cartilage ) and then pumped to all cells in the body. Oxygen Nitrogen Carbon Dioxide Methane Ethanol( Oxygen, Nitrogen, Carbon Dioxide, Methane, Ethanol ) is used by our cells to release energy from food. This is called respiration photosynthesis physical change boiling response( respiration, photosynthesis, physical change, boiling, response ) and produces a waste called carbon dioxide oxygen nitrogen methane ethanol( carbon dioxide, oxygen, nitrogen, methane, ethanol ). This is a toxic gas if it builds up in our bodies so it is transported by the blood from the cells back to the heart before finally being pumped to the lungs where it passes back into the alveoli bronchus trachea rings of cartilage nucleus( alveoli, bronchus, trachea, rings of cartilage, nucleus ) before being exhaled inhaled egested swallowed digested( exhaled, inhaled, egested, swallowed, digested ).