What is Breathing and the Respiratory System? | Types, Definition, Structure, Function & Facts

What is Breathing and the Respiratory System?

Humans breathe through what is known as the respiratory system. This system is mainly made up of our lungs and windpipe.

Why do we have to breathe?

Our body is a very complex system. Energy is one of the things it needs. When we eat, our bodies digest food for complex molecules like glucose, which it can use for energy. However, food alone is not enough. Cells also need oxygen to react with glucose to produce energy. We carry oxygen to our cells with the respiratory and breathing systems.

Breathing In

We breathe using a muscle called the diaphragm. It flattens out, causing our lungs to expand and fill with air. When we breathe in, air is pushed through the nose or mouth, into the windpipe, and into the bronchi of the lungs. These bronchi branch off and become smaller and smaller, like roots or branches.


No, it’s not some kind of pasta! At the ends of the smaller branches of the bronchi are small air sacs called alveoli. These air sacs have very thin single cell walls that allow oxygen to pass to the red blood cells as they pass through. There are hundreds of millions of these little guys in our lungs.

Breathing Out

The alveoli not only transport oxygen to our blood, but also help clean the exhaust gas from our blood cells. This exhaust gas is carbon dioxide. When we need to exhale carbon dioxide from the lungs, the diaphragm tilts and pushes the air out, removing the carbon dioxide. This gives way to fresh air with fresh oxygen returning in our next breath.

Our Nose

The nose does more to breathe than just providing a place for air to enter our bodies. It also helps to filter the air of dust and other things. It does this by using a lot of hair and mucus. It also helps to warm the air before it reaches our lungs.

Why do we get out of breath?

When we run or do strenuous activity, our muscles burn energy and consume oxygen from red blood cells. To try to get more energy and oxygen to these cells, our heart pumps faster to push more blood to the lungs. At the same time, our lungs will try to breathe harder and faster to get more oxygen. Eventually, we feel short of breath and need rest for our body to recover.


The respiratory system also helps with speech. We cannot talk without air. By forcing air through our vocal cords, the respiratory system helps them vibrate and produce sounds such as speaking, singing or shouting.

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