The species theory, polygenism, held that human races were of different lineages and suggested a hierarchy outlined in the Chain of Being that positioned Africans between man and lower primates.
No, they are involved in the Circulatory System which is responsible for pumping and channelling blood to and from the body and lungs with heart, blood and blood vessels. no veins are not considered an organ because they are a grouping of different tissues like a organ.
Only veins have valves. Arteries have a smaller lume. An artery carries blood away from the heart, while veins transport blood to the heart. The difference is that an artery brings blood to the body and a vein takes blood to the lungs.Arteries and Veins are part of the circulatory system, where arteries carry the blood from the heart to the organs, and the veins carry it from the organs to the heart again.hen the arteries deposit the oxygen and other nutrients through the capillaries, the blood then moves to the veins, which will carry the blood back to the heart. The veins are made from all the capillary branches moving back to gether.