How the Body Works: The Transport of Oxygen

The transport of oxygen and carbon dioxide between the lungs and tissue cells is the prime function of red blood cells. Essentially, red cells are packets of hemoglobin, a molecule which readily combines with oxygen. As the red cells flow through the body tissues, oxygen diffuses from them to the tissues in exchange for carbon dioxide. The deoxygenated red cells carry a little carbon dioxide, then pass through the bloodstream to the lungs. Here the reverse exchange of oxygen and carbon dioxide takes place. The oxygenated red cells are then conducted back to the body tissues.