Why do we breathe?

Oxygen is essential for life.

Normal air contains 21% oxygen, which we breathe into our lungs so it can enter our bloodstream to help with the proper functioning of our tissues and organs.

We also breathe as a way to expel carbon dioxide gas, which is a type of waste our bodies produce.

Understanding the respiratory system

The respiratory system is the system of organs that allow us to breathe. It’s made up of two sections:


The upper airway

includes the nose and mouth, where air enters the body and travels through the windpipe - also known as the trachea. From there the air you breathe enters the lower airway.


The lower airway

includes the lungs, diaphragm and two bronchi, which are tubes that connect the trachea to the lungs. The diaphragm is beneath the lungs and moves up and down to push and pull air through the respiratory system.


How breathing works

The process of breathing (or respiration) has two distinct phases: inhalation and exhalation.

While you can consciously make an effort to inhale and exhale, breathing is an automatic reflex that is controlled by your nervous system.


The normal breathing process starts when the diaphragm, the muscle located under your lungs, contracts (tightens) and moves downward.

  • This increases the space in your chest cavity, into which your lungs expand.
  • As your lungs expand, air enters your nose or mouth and is warmed and moistened.
  • It then travels down your windpipe to your bronchial tubes – the tubes that connect your windpipe to your lungs.
  • When the air reaches your lungs it enters the alveoli (air sacs), where oxygen is passed into your bloodstream.


When you breathe out, or exhale, your diaphragm relaxes and moves up into your chest cavity.

As the space in your chest cavity gets smaller, air rich in carbon dioxide is forced out of your lungs and windpipe, and then out your nose or mouth.

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What can cause breathing problems?

  • Respiratory conditions that affect the muscles, nerves, reflexes or organs involved in breathing can make taking a breath very difficult.
  • Chronic lung conditions can disrupt normal breathing, where people cannot breathe in enough oxygen, exhale out enough carbon dioxide, or both.

Keep exploring

What are respiratory diseases and conditions?

Learn about the types of conditions that can affect your breathing.

What is COPD?

Learn about COPD and available treatment options. 

What is mechanical ventilation (non-invasive and invasive)?

Find out what your options are if you need mechanical ventilation.