By the time you’re 30 years old you will have breathed in about 300 decillion oxygen molecules
Contents Your Beating Heart Breathing Blood Circulation Heartbeat Arteries and Veins How Cells Breathe What Is Blood Blood in Action Mending Hearts Staying Fit Speaking and Singing The History of the Heart More Hearty Facts Index 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Your Beating Heart Every cell in your body needs a nonstop supply of oxygen from the air Without it cells in your brain die in minutes To keep up this vital supply your body has two interlocking systems Scientists call them the respiratory and cardiovascular systems but they just mean breathing and blood circulation Big-hearted The biggest heart in the world belongs to the blue whale It’s about the size of a bumper car at the fair and weighs about 440 pounds 200 kilograms If you’re very small you might even be able to squeeze inside its main outflow pipe the aorta and into the pumping chamber inside Your heart is about the size of an apple Yet apart from its size the whale’s heart is pretty much like yours Breathing Air The average human being breathes in about 145 gallons 550 liters of oxygen per day So around the world people breathe in nearly 1 trillion gallons 4 trillion L of oxygen We breathe out about 800 billion gallons 3 trillion L of carbon dioxide 6
Love Hearts The heart has been associated with love since ancient times And we often tag Internet posts with a heart symbol Yet the heart symbol is nothing like the shape of your own heart which has no particular shape at all Scholars think the heart symbol was developed in the late Middle Ages Faint-hearted Diseases related to the heart are now the biggest cause of early death around the world And they are going up rapidly In 1990 over 12 million people died of heart disease In 2013 it was over 17 million It is thought that this may be because more people are living to the age when heart disease is a risk Heart Memories In the past people thought memories were stored in the heart as well as the brain And it may be that heart cells have some kind of memory The evidence is thin but a few patients who received a heart transplant seemed to develop the same odd tastes in food as the donors who gave them their new hearts 7
