Oxygen is the most important substance for human life, because without it we can live only a few minutes. All living tissue in need of energy for living and functioning, which they obtain as a result of combustion of a fuel (in the form of sugars, fats, and proteins). However, in order to have the combustion process, it is necessary to the presence of oxygen. Oxygen is delivered to cells via the blood, which takes it into the lungs during each inhalation, and then it flows to the heart to be at the next wypchniętą shrinkage of the artery move and travel throughout the body and obtain all of the cells in życiodajny oxygen.
You can see that in order to get oxygen to the cells, there is a cooperation of the two major systems: the respiratory system - responsible for the exchange of gases between an organism and the environment and the blood system - responsible for the transport of gases between the lungs and cells.