Humans Breathe (respiratory system)

When we breathe, we inhale (take in) oxygen to the body and exhale (let out) carbon dioxide. Our chest moves up and down. The number of chest movement is the rate of breathing. Your respiratory system is made up of the organs in your body that help you to breathe.
Breathing starts with a dome-shaped muscle at the bottom of the lungs called the diaphragm. When you breathe in, the diaphragm contracts, when it contracts it flattens out and pulls downward. This movement enlarges the space that the lungs are in. This larger space pulls air into the lungs. When you breathe out, the diaphragm expands reducing the amount of space for the lungs and forcing air out. The diaphragm is the main muscle used in breathing.
As we inhale, the chest rise outwards and upwards cause the chest to expand. The air is taken in through the nose, down the windpipe into the lungs. This air contains more oxygen.

As we exhale, the chest moves in causing the chest to contract. The air inside the lungs then flows out from the lung to the windpipe and then out though the nose. This air contains more dioxide.