Blood group antigens are carbohydrates that are attached to proteins or lipids. An antigen is a substance foreign to the body that causes an immune response. An immune response occurs when antibodies, which are proteins in your immune system, are summoned to attack an antigen.
Blood that reaches the lungs travels throughout a network of small blood vessels, where oxygen moves into the blood and carbon dioxide moves out of the blood, according to the National Heart, Lung and Blood Institute.
The alveoli in your lungs are covered with tiny blood vessels called capillaries. It's there in your alveoli that the oxygen in the air you breathe passes into your blood via the capillaries. From your capillaries, the oxygenated blood travels to the heart, where it's pumped out to the rest of the cells in your body. The air you breathe every day is important to your health, but did you realize that air pollution can make breathing more difficult and even cause all sorts of health problems? 2  Jump online to check out the Clean Air Detective Follow the instructions to do a basic investigation of the air you breathe every day.