Blood vessel vessels function to transport blood. In general, arteries and arterioles transport oxygenated blood from the lungs to the body and its organs, and veins and venules transport deoxygenated blood from the body to the lungs. Blood vessels also circulate blood throughout the circulatory system Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95–100%) with oxygen. In all veins apart from the pulmonary vein, the saturation of hemoglobin is about 75%. (The values are reversed in the pulmonary circulation.) In
Blood red dark red state, but quickly oxygenates upon exposure to air, turning a brighter shade of red. This happens more quickly with smaller volumes of blood such as a pinprick and less quickly from cuts or punctures that cause greater blood flows such as a puncture in the basilic vein: all blood collected during a phlebotomy procedure is deoxygenated blood, and it does not usually have a chance to become oxygenated upon leaving the body. Arterial blood, which is already oxygenated, is also already a brighter shade of red— this is the blood see from a pulsating neck, arm, or leg