Process

• Our trachea, or windpipe, takes air down the throat into the entry point of the lungs called bronchi. These two tunnels, which split left and right from the trachea, direct air into the our left and right lungs and into the bronchioles. Tens of thousands of these tiny tubes cover the lungs and dead end into tiny sacs called alveoli.
  
  

Exchange

• The average adult lung contains enough alveoli to cover the area of a tennis court. More than 600 million of these spongy little sacs fill with air, delivering it to our blood cells through its connection with our pulmonary arteries and veins. This is where the exchange of crucial gas takes place.
  
  

Circulation

• The alveoli are densely surrounded by a network of blood vessels, also known as capillaries. These vessels connect directly to the heart, using oxygenated blood to power our heart. Two types of blood vessels are necessary to create a give and take of oxygenated and de-oxygenated blood. Pulmonary arteries carry used (or de-oxygenated) blood away from the heart to the lungs to be refreshed with oxygen. The oxygenated blood then travels back to the heart through pulmonary veins.