Introduced by Big Red: All the blood vessels in the human body are connected into a continuous pipe and connected with the heart. Human blood vessels include arteries, capillaries and veins, which are densely intertwined into a network. An adult has more than 100 billion blood vessels, large and small. If they were connected end to end, they would be more than 100,000 kilometers long and could circle the earth's equator two and a half times.

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