Glossary of Terms
The organs responsible for adding oxygen to the blood after removing the body's carbon dioxide (CO2). The lungs are located in the chest and lie on either side of the heart. The lungs are composed of millions of tiny air sacs, known as alveoli. As a person breathes in, the alveoli are filled with fresh air. The heart pumps the blood that has been "used" by the body to the lungs. As the "used" or un-oxygenated blood passes by the alveoli, the CO2 in the blood moves into the alveoli, while the oxygen moves into the blood. The newly oxygenated blood is then transported back to the heart, which pumps out the newly oxygenated blood back out to the body. The air in the alveoli, which is now oxygen depleted, is exhaled out with the exchanged CO2.