Hold out your hand and make a fist. If you're a kid, your heart is about the same size as your fist, and if you're an adult, it's about the same size as two fists. Your heart beats about 100,000 ...

The idea that the heart is about the same size as a person's fist comes from anatomical observations. When looking at a human heart, its general size closely matches the size of the clenched fist ...