Blood is a substance that is VERY important for humans. It has cells that fight off diseases, carries Oxygen around our body, and carries glucose (a form of sugar) around our body to give us energy! Blood travels thorugh vessels, which are very long tubes made mostly out of tissue and muscles. The blood vessels have to reach all over your body and are squeezed into a compact space in your body.
How can out blood vessels wrap around the Earth? It is because they are so long! These blood vessels have to reach every single part of your body, from your heart and lungs to your brain and stomach! They are squeezed into this small space (our bodies) and have to reach every part of our body for us to survive! That is how blood vessels could circle around the Earth! That is about 24,900 miles!