Did you give your friends valentines and little heart-shaped
candies on Valentine's Day? Do you ever cross your heart when
making a promise that you really, really mean? Or turn on the radio
to hear a guy singing about his broken heart?
We see and hear about hearts everywhere. A long time ago, people
even thought that their emotions came from their hearts, maybe
because the heart beats faster when a person is scared or excited.
Now we know that emotions come from the brain, and in this case,
the brain tells the heart to speed up. So what's the heart up
to, then? How does it keep busy? What does it look like? Let's
Working That Muscle
Your heart is really a
. 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 the heart 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
Your heart 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.
We Got the Beat
How does the heart beat? Before each beat, your heart fills with
blood. Then its muscle contracts to squirt the blood along. When
the heart contracts, it squeezes - 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. The heart is one hard worker!
The heart is made up of four different blood-filled areas, and
each of these areas is called a
. There are two chambers on each side of the heart. One chamber is
on the top and one chamber is on the bottom. The two chambers on
top are called the
-tree-uh). If you're talking only about one, call it an atrium.
The atria are the chambers that fill with the blood returning to
the heart from the body and lungs. The heart has a
The two chambers on the bottom are called the
-trih-kulz). The heart has a
. Their job is to squirt out the blood to the body and lungs.
Running down the middle of the heart is a thick wall of muscle
-tum). The septum's job is to separate the left side and the
right side of the heart.
The atria and ventricles work as a team - the atria fill with
blood, then dump it into the ventricles. The ventricles then
squeeze, pumping blood out of the heart. While the ventricles are
squeezing, the atria refill and get ready for the next contraction.
So when the blood gets pumped, how does it know which way to
Well, your blood relies on four special
inside the heart. A valve lets something in and keeps it there by
closing - think of walking through a door. The door shuts behind
you and keeps you from going backward.
Two of the heart valves are the
-trul) valve and the
-pid) valve. They let blood flow from the atria to the ventricles.
The other two are called the
-tik) valve and
-muh-ner-ee) valve, and they're in charge of controlling the
flow as the blood leaves the heart. These valves all work to keep
the blood flowing forward. They open up to let the blood move
ahead, then they close quickly to keep the blood from flowing
It's Great to Circulate
You probably guessed that the blood just doesn't slosh
around your body, once it leaves the heart. It moves through many
tubes called arteries and veins, which together are called blood
vessels. These blood vessels are attached to the heart. The blood
vessels that carry blood
the heart are called arteries. The ones that carry blood
the heart are called veins.
The movement of the blood through the heart and around the body
-shun), and your heart is really good at it. It's so good at it
that it takes less than 60 seconds to pump blood to every cell in
Your body needs this steady supply of blood to keep it working
right. Blood delivers oxygen to all the body's cells. To stay
alive, a person needs healthy, living cells. Without oxygen, these
cells would die. If that oxygen-rich blood doesn't circulate as
it should, a person could die.
The left side of your heart sends that oxygen-rich blood out to
the body. The body takes the oxygen out of the blood and uses it in
your body's cells. When the cells use the oxygen, they make
and other stuff that gets carried away by the blood. It's like
the blood delivers lunch to the cells and then has to pick up the
Kidneys Are Filters
Each time the blood circulates from the heart out to the body,
about 20% (one fifth) of it goes through the
. The kidneys filter out some of the waste before the blood heads
back to the heart.
The returning blood enters the right side of the heart. It takes
the blood to the lungs for a little freshening up. Carbon dioxide
is left in the lungs to be removed when we exhale. What's next?
An inhale, of course, and a fresh breath of oxygen that can enter
the blood to start the process again. And remember, it all happens
in about a minute!
Listen to the Lub-Dub
When you go for a checkup, your doctor uses a stethoscope to
listen carefully to your heart. A healthy heart makes a lub-dub
sound with each beat. This sound comes from the valves shutting on
the blood inside the heart.
The first sound (the lub) happens when the mitral and tricuspid
valves close. The next sound (the dub) happens when the aortic and
pulmonary valves close after the blood has been squeezed out of the
heart. Next time you go to the doctor, ask if you can listen to the
Pretty Cool - It's My Pulse!
Even though your heart is inside you, there is a cool way to
know it's working from the outside. It's your pulse. You
can find your pulse by lightly pressing on the skin anywhere
there's a large artery running just beneath your skin. Two good
places to find it are on the side of your neck and the inside of
your wrist, just below the thumb.
You'll know that you've found your pulse when you can
feel a small beat under your skin. Each beat is caused by the
(squeezing) of your heart. If you want to find out what your heart
rate is, use a watch with a second hand and count how many beats
you feel in 1 minute. When you are resting, you will probably feel
between 70 and 100 beats per minute.
When you run around a lot, your body needs a lot more
oxygen-filled blood. Your heart pumps faster to supply the
oxygen-filled blood that your body needs. You may even feel your
heart pounding in your chest. Try running in place or jumping rope
for a few minutes and taking your pulse again - now how many beats
do you count in 1 minute?
Keep Your Heart Happy
Most kids are born with a healthy heart and it's important
to keep yours in good shape. Here are some things that you can do
to help keep your heart happy:
- Remember that your heart is a muscle. If you want it to be
strong, you need to exercise it. How do you do it? By being
active in a way that gets you huffing and puffing, like jumping
rope, dancing, or playing basketball. Try to be active every
- Eat a variety of healthy foods and avoid foods high in
unhealthy fats, such as saturated fats and trans fats.
- Don't smoke. It can damage the heart and blood
So now you know that your heart doesn't look like a
valentine, but it sure deserves to be loved for all the work it
does. It started pumping blood before you were born and will
continue pumping throughout your whole life.
Steven Dowshen, MD
Date reviewed: November 2007
Originally reviewed by:
Gina Baffa, MD
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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