An adult's blood vessels are long enough to wrap around the Earth four times.

The human body has three main types of blood vessels. Arteries carry blood away from the heart. Veins bring blood back to the heart. Capillaries are the smallest vessels and connect the two.An average adult has about 100,000 miles of these vessels. The Earth is about 24,901 miles around at the middle. This means your blood vessels could circle the planet four times. A child's body has about 60,000 miles of vessels.Capillaries are very thin. They are about 5 to 10 micrometers wide. This is the same width as a single red blood cell. There are billions of these tiny tubes in your body.The heart pumps 2,000 gallons of blood through this system every day. This movement delivers oxygen and food to cells. It also helps the body stay at the right temperature. No cell in the body is more than a tiny distance away from a capillary.