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 from the air to cells. When we breathe in oxygen enters the small air sacs, called alveoli, in the lungs. Oxygen diffuses from there into the bloodstream. Oxygen is not carried in the plasma, but is carried by the red blood cells.These contain a red substance called haemoglobin, which joins onto oxygen and carries it around the body in the blood, then lets it go when necessary.he carbon dioxide produced during respiration diffuses out of the cells and into the blood plasma. The blood carries it to the lungs. It then diffuses across the walls of the alveoli and into the air, ready to be exhaled. 1  Page. 2  1. 3  2. 4  3. 5  4. 6  5.