The oxygen in inhaled air passes across the thin lining of the air sacs and into the blood vessels. This is known as diffusion. The oxygen in the blood is then carried around the body in the bloodstream, reaching every cell. When oxygen passes into the bloodstream, carbon dioxide leaves it.
Once the oxygen diffuses across the alveoli, it enters the bloodstream and is transported to the tissues where it is unloaded, and carbon dioxide diffuses out of the blood and into the alveoli to be expelled from the body.
Atoms are the most basic confirmed building block of life. Everything is made up of atoms. Atoms are made the positively charged protons, neutral charged neutrons, and negatively charged electrons.
