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Circulatory System  About the Cardiovascular System  Lee este
articulo  The heart and circulatory system (also called the
cardiovascular system) make up the network that delivers blood
to the body's tissues. With each heartbeat, blood is sent
throughout our bodies, carrying oxygen and nutrients to all of
our cells.  Body Basics: Heart  Every day, the approximately 10
pints (5 liters) of blood in your body travel many times through
about 60,000 miles (96,560 kilometers) of blood vessels that
branch and cross, linking the cells of our organs and body
parts. From the hard-working heart, to our thickest arteries, to
capillaries so thin that they can only be seen through a
microscope, the cardiovascular system is our body's lifeline.
The Heart  The heart is the key organ in the circulatory system.
As a hollow, muscular pump, its main function is to propel blood
throughout the body. It usuall