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.
Oxygen travels into the smallest air sacs of the lungs, called alveoli. Capillaries around these air sacs allow blood to exchange oxygen for unwanted carbon dioxide.The oxyge â¦ n-rich blood then returns to the heart to be pumped to the rest of the body. The carbon dioxide in the lungs is passed out of the body through the mouth and nose when we exhale.apillaries around these air sacs allow blood to exchange oxygen for unwanted carbon dioxide. The oxyge â¦ n-rich blood then returns to the heart to be pumped to the rest of the body. The carbon dioxide in the lungs is passed out of the body through the mouth and nose when we exhale.