How do humans breathe?

Learn about the lungs and human respiration system.

Why do we breathe?

All living things need oxygen to survive. Our bodies use it to turn the fuel from our food into energy.

What happens when we breathe in?

Chest muscles move upwards and outwards. The diaphragm (a muscle under the lungs) moves down.

This makes more space for the lungs which fill up with air from the mouth and nose.

The air moves through tubes in the lungs to tiny air sacs called alveoli. Oxygen passes from these into the blood, which carries the oxygen to all the cells in the body.

What happens when we breathe out?

The alveoli absorb carbon dioxide from the blood.

When we breathe out, the chest muscles move down and inwards. The diaphragm moves up.

This squeeze the lungs and forces air out.

Carbon dioxide from the alveoli flows up through the lungs and out through the mouth and nose.