is really a muscle. It's located a little to the left of the middle
of your chest, and it's about the size of your fist. There are
lots of muscles all over your body - in your arms, in your legs,
in your back, even in your behind. But this muscle is special
because of what it does - the heart sends blood around your body.
The blood provides your body with the oxygen and nutrients it
needs. It also carries away the waste that your body has to get
is sort of like a pump, or two pumps in one. The right side of
your heart receives blood from the body and pumps it to the lungs.
The left side of the heart does the exact opposite: it receives
blood from the lungs and pumps it out to the body. By the time
you're grown up, your heart will be beating (pumping) about 70
times a minute.
How does the
heart beat? Before each beat, your heart fills with blood. Then
it contracts to squirt the blood along. When something contracts,
it squeezes tighter - try squeezing your hand into a fist. That's
sort of like what your heart does so it can squirt out the blood.
Your heart does this all day and all night, all the time. Every
day, an adult heart pumps 2,000 gallons (7,500 liters) of recycled
blood by filling and contracting. The heart is one tough worker!