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.
Vascular tissues in the human body have blood vessels like veins, arteries and capillaries, while avascular tissues do not. For example, muscle tissue is vascular, or vascularized.Tissues with a lot of blood vessels, like those in the lungs and liver, are said to be highly vascularized.. A few structures in the human body lack blood vessels, like the lens of the eye.Since blood vessels would obscure vision in this structure, it must be avascular.issues with a lot of blood vessels, like those in the lungs and liver, are said to be highly vascularized.. A few structures in the human body lack blood vessels, like the lens of the eye. Since blood vessels would obscure vision in this structure, it must be avascular.