How is oxygen and carbon dioxide transported in human beings?

A lot of people wonder where oxygen and carbon dioxide go when they inhale and exhale. Well, the process is actually quite simple:

When you inhale, your diaphragm contracts and flattens out, which reduces the pressure inside your lungs. The greater atmospheric pressure on the outside pushes oxygen molecules into your body through tiny openings in your respiratory tract called "alveoli." As this happens, other gasses such as nitric oxide or argon collect in these alveoli as well. The air you exhale now contains less oxygen than it did previously because some was absorbed by your body's tissues and organs - but it still has those other gases present.