An externality is defined as a benefit or cost that is imposed on a third party, such as society, other than the producer or consumer of a good or service, or, more simply, an economic side effect. The more of a product that is consumed or produced, the more of an externality that results.
Arteries carry oxygenated blood (with the exception of the pulmonary artery and umbilical artery). Veins carry deoxygenated blood (with the exception of pulmonary veins and umbilical vein).
Save. Arteries and veins are both vessels in the circulatory system that carry blood through the body. The difference between the two is that arteries carry blood away from the heart and veins carry blood back to the heart.