Page 191 - The Miracle of the Blood and Heart

The Heart: The Most Efficient
Machine in the World

place, the valves close again to prevent the blood's return to
the atria where it came from.
Similar valves also exist in the ventricles. When the ventri-
cles contract, these valves open and let the blood flow direct-
ly to the body. Then the valves close, preventing the pumped
blood from returning to the heart. The sound that you per-
ceive as your heartbeat does not result from the heart's con-
traction and dilation, as is popularly imagined. Listening to
your heartbeat, you are actually hearing the opening and clos-
ing of these four powerful valves.
Leaving aside this flawless system's enormous complexity,
even just the rhythmic opening and closing of the valves pre-

superior vena cava aorta

left pulmonary
artery
right pulmonary
arteries left pulmonary
veins
right pul-
monary veins left atrium
right atrium cardiac
vein
heart valve muscles
coronary
artery

valve closed valve open
inferior vena cava right ventricle left ventricle
The venae cavae bring deoxygenated blood to the right side of the heart,
and the pulmonary arteries carry that blood to the lungs. The pul-
monary veins bring oxygenated blood from the lungs to the left side
of the heart, and the aorta sends this blood to the body. During this Adnan
flow of blood, the heart valves contract, thus allowing blood to pass
through the chambers. Oktar

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