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How the Respiratory System Works

Tap an organ to see its role in breathing.

Nose and Mouth

The entry points for air, where the nose in particular warms, moistens, and filters incoming air through tiny hairs and mucus before it travels further into the body.

Trachea (Windpipe)

A rigid tube reinforced with cartilage rings that carries air from the throat down toward the lungs, splitting into two branches at its base.

Bronchi

The two main branches that the trachea divides into, one leading to each lung, which then continue splitting into progressively smaller passages called bronchioles.

Lungs

The two large, sponge-like organs that house the branching airways and alveoli, expanding and contracting with the help of the diaphragm to draw air in and push it out.

Alveoli

Tiny, grape-like clusters of air sacs at the end of the smallest airways, surrounded by capillaries, where the actual exchange of oxygen and carbon dioxide with the blood takes place.

Diaphragm

A large dome-shaped muscle beneath the lungs that contracts and flattens to pull air in, then relaxes and rises to push air out, functioning as the primary muscle driving breathing.

A gas exchange happening constantly, without conscious thought

This page is for general educational information only and is not a substitute for professional medical advice. The human body contains roughly 300 to 500 million alveoli, providing an enormous surface area β€” often compared to the size of a tennis court when unfolded β€” dedicated entirely to the efficient exchange of oxygen and carbon dioxide.

Frequently Asked Questions

Why do we breathe faster during exercise?

Physical activity increases the body's demand for oxygen and produces more carbon dioxide as a byproduct, so the brain signals the respiratory system to increase breathing rate and depth to meet that increased demand and remove the excess carbon dioxide.

Is the left lung the same size as the right lung?

No β€” the left lung is slightly smaller than the right lung to make room for the heart, which sits slightly to the left side of the chest cavity.