Why and how do we breathe?

How often do we breathe every day? Why? And what exactly happens when we breathe? Why do we need oxygen? What is internal and external respiration? A journey through the body.

We do it without even thinking about it: breathing. Inhaling and exhaling. We don’t even realise we’re doing it and how often we’re doing it. And we do it around 20,000 times a day. But what actually happens when we breathe? How do our respiratory organs actually work?

How do we breathe?

When we inhale, a strong muscle under the lungs called the diaphragm flexes downwards. At the same time, the chest and lungs expand and fill with air. The oxygen in the air is inhaled through the nose and mouth and travels through the trachea into the lungs and through the ever smaller airways branching off into bronchi and bronchioles into the alveoli and finally into the small blood vessels (capillaries). Here it passes into the blood. The oxygenated blood travels to the cells. The capillaries then return the ‘used air’, the CO2, to be exhaled.

Internal and external respiration

A distinction is made between internal and external respiration. External respiration is the exchange of gases in the lungs. Oxygen from the outer environment is inhaled and carbon dioxide is expelled. We can draw in up to four litres of air with every breath.

Internal respiration involves a biochemical process in which oxygen is released into the cells and used for producing energy for the body. With the help of the oxygen, the glucose gained from nutrition is broken down into CO2 and water. Energy is released and bound in the form of a molecule known as ATP, or adenosine triphosphate. We need ATP for all processes within the body – be it for the brain, the muscles or digestion.

Nose or mouth breathing?

When we breathe through the nose, the air is warmed, cleansed and humidified before being passed to the lungs. This is not the case when we breathe through our mouth. However, we generally only breathe through our mouth when insufficient oxygen passes through the nose.


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