
Your heart beats 101,000 times a day. During your lifetime it will beat about 3 billion times and pump about 800 million pints (378 million litres) of blood. A normal heart beats 70 to 80 times a minute. Over 70 to 80 years, it gives a few billion beats. It is the powerful machine inside you.
A heart consists of two pumps, each made of two chambers. The right atrium squirts oxygen-depleted blood from the body into the right ventricle, which pumps it to the lungs. The left atrium squirts aerated blood from the lungs into the left ventricle, which pumps it out to the body. With each heartbeat, the two small atria contract together, then...