Lung

Structure

Each lung is divided into lobes and contains a branching tree of airways ending in millions of tiny alveoli. The right lung has three lobes; the left has two and a notch where the heart sits.

Function

Air drawn into the alveoli by chest wall and diaphragm movement diffuses across thin walls into surrounding capillaries. Carbon dioxide travels in the opposite direction and is exhaled.

Clinical note

Pneumonia, asthma, and chronic obstructive pulmonary disease all impair gas exchange and produce shortness of breath.