How is the human respiratory system related to the circulatory system?

The gives us oxygen while the distributes it.

Well, if you are familiar with the circulation of the blood, you can see that the blood goes to the heart, into the lungs, back to the heart, into the body, then back to the heart.

The blood harvests oxygen inside the lungs and releases the carbon dioxide into the lungs to be expelled and exhaled.

So like the kidney, the lungs serves as a cleaning system for the blood and the body.