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Capítulo 1 Introdução
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| The dynamic process by which
the single-cell human zygote
becomes a 100-trillion-cell
adult is perhaps
the most remarkable
phenomenon in all of nature.
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| Researchers now know that many
of the routine functions
performed by the adult body
become established
during pregnancy -
often long before birth.
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| The developmental period
before birth
is increasingly understood
as a time of preparation
during which
the developing human
acquires the many structures,
and practices
the many skills, needed
for survival after birth.
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Capítulo 2 Terminologia
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| Pregnancy in humans normally
lasts approximately 38 weeks
as measured from the time
of fertilization,
or conception, until birth.
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| During the first 8 weeks
following fertilization,
the developing human
is called an embryo,
which means "growing within."
This time, called
the embryonic period,
is characterized
by the formation
of most major body systems.
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| From the completion of 8 weeks
until the end of pregnancy,
"the developing human
is called a fetus,"
which means "unborn offspring."
During this time,
called the fetal period,
the body grows larger and
its systems begin to function.
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| All embryonic and fetal ages
in this program
refer to the time
since fertilization.
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