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.
Report Abuse. Blood leaves the heart through vessels called arteries. When blood leaves the heart on it's way to the lungs, from the right ventricle, it leaves in the pulmonary arteries to the lungs. The pulmonary arteries are the only arteries in the body that carry deoxygenated blood. Blood returns from the lungs to the heart in the pulmonary veins.