The circulatory and respiratory systems work together by the person breathing. They are actually connected because the respiratory system is because its the lungs. The lungs provide air for the for the body. The circulatory system is were the heart is placed. When the body breaths in air it expands the lungs and takes out co2, once the lungs expand it pumps the heart to keep pumping blood to the body which provides everything else in the body. If the heart doesn't have air/blood going thru it its starts to panic and die slowly.