RESPIRATORY SYSTEM

Humans breathe through something called the respiratory system. This system is made up primarily of our lungs and windpipe.

Why do we have to breathe?
Our body is a very complex system. One of the main things it needs is energy. When we eat our body digests the food to get complex molecules like glucose, which it can use for energy. However, food alone isn't enough. The cells also need oxygen to create energy. We get the oxygen to our cells with the respiratory system and by breathing.


Breathing In
We breathe in using a muscle called the diaphragm. It flattens out making our lungs expand and fill with air. When we breathe in, air gets forced through our nose or mouth, down our windpipe, and into bronchi tubes in our lungs. These bronchi tubes branch out and get smaller and smaller, like the roots or branches of a tree.


Alveoli
At the end of the smallest branches of the bronchi are tiny air sacs called alveoli. These air sacs have a very thin, one cell thick wall that allows oxygen to be passed to red blood cells as they are passing by. 

Breathing Out
The alveoli don't just pass oxygen to our blood, they also help to clean out waste gas from our blood cells. This waste gas is carbon dioxide. When we need to breathe the carbon dioxide out of our lungs, the diaphragm bows up and pushes the air back out, getting rid of the carbon dioxide. This makes room for fresh air with new oxygen to come back in on our next breath.


Our Nose
The nose does more for breathing than just providing a place for air to enter our body. It also helps to filter the air of dust and other stuff. It does this by using lots of hairs and mucus. It also helps warm up the air prior to getting to our lungs.