Chapter 2

Human Breathing

Learn how your lungs take in oxygen and push out carbon dioxide.

Every second of the day you are breathing, even while you sleep! Breathing helps your body take in the gas it needs to stay alive and let out a gas it does not need.

Breathing in and out

When you breathe in (inhale), you take in air that has oxygen. Your body needs oxygen to work and to give you energy. When you breathe out (exhale), you push out carbon dioxide, a waste gas your body does not need.

Key idea

Breathe in oxygen. Breathe out carbon dioxide. Your two lungs do this job.

Parts that help you breathe

  • Nose — air enters here and is warmed and cleaned.
  • Windpipe — a tube that carries air down to the lungs.
  • Lungs — two soft organs where oxygen passes into the blood.

Example

When you run in the field, your body needs more oxygen, so you breathe faster and take deeper breaths. When you rest, your breathing slows down again.

Remember

  • We breathe in oxygen and breathe out carbon dioxide.
  • Breathing in and out again and again is called your breathing rate.
  • Keep the air clean so your lungs stay healthy.

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