Page 38 - How It Works - Book of Amazing Answers To Curious Questions, 12
P. 38
AMAZIG ANSWERS TO CURIOUS QUESTIONS ------------------
Superior and inferior vena cava
These large veins carry blood back to the
heart from organs above and below the heart, What's inside
respectively. This blood has already been
stripped of its oxygen supply, and thus is a
dark red or bluish colour.
the heart?
Your heart is a turbocharged double
pumping muscle that beats more than 40
million times every year
ot only does your heart do
Pulmonary veins amazing things, it does so
After the blood collects
oxygen from the lungs, it N tirelessly, every minute of every
returns to the heart via day from the moment you're born (actually,
the pulmonary veins.
even a bit before then) to the instant that
you die. It weighs somewhere between
eight and 12 ounces-slightly more if you're
Left atrium male, less if you're female. Its sole purpose
Blood brimming with is to push blood through your circulatory
oxygen and other
nutrients collects here. system, providing crucial oxygen and
When the atrium other nutrients to all your organs.
contracts, the blood The heart is considered a double pump
passes through the
mitral valve and because the right half sends 'used' blood
enters the left ventricle to your lungs. There, the blood drops off a
load of carbon dioxide and picks up some
fresh oxygen, which you have helpfully
provided by breathing. Then the
oxygenated blood returns to the left half
of the heart. This 'heart-to-lungs-to-heart
again' trip is known as pulmonary
circulation. The left side of the heart then
pumps this oxygenated blood to every
organ in your body other than your lungs.
Your brain, your skin, the muscles in your
thigh, your spleen - they all get blood
(and therefore oxygen) by virtue of your
beating heart.
Even the heart itself gets blood, via a
special set of veins and arteries known as
Blood from the vena the coronary system. The myocardia I
cava enters this
chamber of the muscle within the wall of the heart needs
heart, where it oxygen and other nutrients to keep
collects passively.
beating. Unfortunately, the coronary
arteries that do this job are very narrow,
between 1.7 and 2.2 millimetres in
Tricuspid valve
diameter. If they become clogged with
When the right atrium contracts, it
pushes blood through the tricuspid cholesterol or other fatty deposits, the
valve, a one-way valve leading down Left ventricle heart stops working. This is bad for you.
into the right ventricle. The left ventricle must send
blood on a longer journey Of course, the relatively simple concept
than the right ventricle, so it of the double pump is fairly complex in
has thicker walls and uses practice. A series of valves control blood
Right ventricle about three times as much
Blood enters the right ventricle under pressure from the atrium's contraction, energy. Luckily, the left flow to the heart's four chambers, allow
giving it a boost much like the turbocharger in a high-performance car. The atrium's contraction gives for the build-up of enough blood pressure
ventricle contracts and pumps blood through the pulmonary valve, into the the left ventricle's output a
pulmonary artery and toward the lungs. 20 per cent boost to get the job done, and direct the blood to
the correct veins and arteries.
38 How It TtOrks WorldMags.net
WorldMags.net
