Humans breathe to get oxygen into the body and to remove carbon dioxide, a waste gas produced by cells.
Oxygen and energy
Every cell uses oxygen to help convert nutrients from food into usable energy in a process called cellular respiration. Without a continuous supply of oxygen, this energy production quickly fails and cells begin to die, especially in the brain and heart.
Getting rid of carbon dioxide
As cells make energy, they produce carbon dioxide, which can make the blood too acidic if it builds up. Breathing out removes this carbon dioxide from the blood in the lungs, helping keep the body’s pH in a safe range.
How the body makes you breathe
The brainstem automatically controls breathing by sensing carbon dioxide levels in the blood more than oxygen levels. When carbon dioxide rises, the brain increases breathing rate and depth, which brings in more oxygen and blows off extra carbon dioxide.
What the lungs actually do
When you inhale, air travels down the airways into millions of tiny sacs in the lungs where oxygen moves into the blood and carbon dioxide moves out. The circulatory system then carries oxygen to tissues and returns carbon dioxide to the lungs to be exhaled, completing the cycle.
