Our fourth subject for study in the series is our heart. This is our amazing blood pump, which sends about seven and a half tonnes of blood around our body every single day, delivering this fresh delivery to the tens of trillions of cells in the body through its 100,000 miles of blood vessels. Our hearts beat more than 100,000 times a day to do this job. It is hardly surprising therefore that the human heart has been called one of the biggest engineering miracles in the whole world.
