Heart

Heart
Your heart works all of the time to pump blood to al parts of your body and back again. This makes sure that every cell gets oxygen and food. When you are resting your heart beats at 70 times a minute, but speeds up when you run around. In just one minute all of your blood goes around your whole body. If you live to be 80, your heart will beat 3 billion times without stopping. Your heart is the size of your fist. Your heart is located between your lungs. Your ribs go round your heart to protect it.

Source - "Body" by Robert Winston, DK, 2005. Source - picture - http://en.wikipedia.org/wiki/File:Humhrt2.jpg