What are the lungs? The lungs are two spongy organs found in the chest. They are responsible for delivering oxygen to the bloodstream. When you take a breath in, air moves into the lungs causing them to expand. The air can then come very close to blood that is traveling in small vessels called capillaries. When you breathe out, you exhale substances that you don't need like carbon dioxide. The lungs are specially designed to place blood in close contact with as much air as possible, so their tissues are very delicate. The right lung has three sections called lobes. The left lung has only two lobes. Air comes in through your mouth and nose and then travels down a tube to the lungs called the trachea. The trachea divides into smaller branches called bronchi, and the bronchi keep dividing and dividing like branches on a tree. As the branches get smaller, they are called bronchioles. At the ... read more on Lung Cancer: The Basics