Spongy organs whose alveoli give a surface area roughly the size of a tennis court for oxygen to pass into blood.
How it works, step by step
The diaphragm contracts and flattens; air is drawn in.
Air reaches the alveoli, wrapped in capillaries.
Oxygen diffuses into blood and binds hemoglobin.
Carbon dioxide diffuses out and is breathed away.
Protection
Mucus and tiny hairs (cilia) trap and sweep particles up and out of the airways.
Practical
Not smoking and limiting exposure to smoke and air pollution are the biggest controllable factors for lung health.
Evidence & sources
Cigarette smoking causes about 80–90% of lung cancer deaths in the US. Evidence: established. Known: Decades of consistent epidemiological and biological evidence. Unknown: Individual risk varies with genetics and exposure history. Source: US Centers for Disease Control and Prevention, Lung Cancer Risk Factors (Current revision).