Describe how the lungs are adapted for gas exchange.

We are going to look at how the lungs are adapted for gas exchange. In humans, we have two lungs. Air passes into the lungs through a tube called the trachea. The trachea splits into two smaller tubes called bronchi, with one passing into each lung. Further into the lung, the bronchi subdivide into smaller tubes called bronchioles. The bronchioles end in tiny air sacs called alveoli. The lungs contain lots of alveoli, and each one is microscopic.
The alveoli are the sites of gas exchange. Oxygen in the air diffuses into the blood stream and carbon dioxide diffuses into the air. The alveoli are adapted to make the rate of gas exchange as fast as possible. The millions of alveoli mean that the lungs have a huge surface area. The alveoli have very thin walls meaning the diffusion path is very short. The alveoli have a very good blood supply.