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Macmillan and Cancerbackup merged in 2008. Together we provide free, high quality information for people affected by cancer through our publications, website and phone service. Find out more|.
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As we breathe in and out, the lungs inflate and deflate with air, taking oxygen into the body and expelling carbon dioxide from the body.
When we breathe in, air passes from our nose or mouth through the windpipe (trachea), which divides into two tubes (airways), one going to each lung. These are known as the right and left bronchus.
They divide to form smaller tubes called bronchioles, which carry air through the lungs. At the end of the bronchioles are millions of tiny air sacs called alveoli. In the alveoli, oxygen is absorbed from the air we breathe in and passes into the bloodstream to be circulated around the body.
Carbon dioxide is a waste gas that must be removed from the body. It passes from the bloodstream into the alveoli and is then breathed out by the lungs.
The right lung has three main areas (known as lobes) and the left lung has two.
Many lung cancers start in the cells lining the bronchi and are called carcinomas of the bronchus.
The lungs and surrounding structures
View a large copy of the diagram showing the lungs and surrounding structures|
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