The respiratory system aids the supply of oxygen to the blood and the evacuation of carbon dioxide. when the heart takes in blood that as shortage of oxygen and abundance of carbon dioxide, the pulmonary arteries pumps such blood to the lungs.
As the lungs increases due to inflow of fresh air from the surroundings, oxygen is transported to enrich low-oxygen blood, and transport the carbon dioxide out of the lungs.
This freshly oxygen rich blood which now have a rich amount of hemoglobin is transported to the heart which then pump or circulated it to the entire body.
