Exchanging oxygen and carbon dioxide 2.3

The primary function of the respiratory system is to exchange oxygen and carbon dioxide. when we breathe in the oxygen goes into our lungs and travels to the aveoli, in the layers of cells that line the aveoli are capillaries these are very small, they carry the oxygen we have breathed in passes into the capillaries, when this happens the unwanted carbon dioxide passes from the blood into the aveoli and then we expel this when we breathe out.
The oxygen rich blood which we have just breathed in travels from our lungs through the pulmonary veins and travels to the left side of the heart, from here it pumps it around the body.
The carbon dioxide rich blood then returns to the right side of the heart, through two large veins called the vena cava, when this happens the blood is pumped through the pulmonary artery back into the lungs. then the cycle begins again.
For all this to take place three processes are needed for the transfer of oxygen from the outside air to the blood in order for this to work in the system, they are known as vetilation, diffusion and perfusion.
Ventilation- is when we breathe in and oxygen goes into the lungs
Diffusion- is the spontaneous movement of the gases and this is done without any effort from the body
Perfusion- is when the cardiovascular system pumps the blood through the lungs