Zygote
:
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fertilization of ovum and sperm
Begins of day 0 till day 14
Divides through mitosis
Known as germinal period
Zygote lasts about 4 days
After 5th day it will change to blastocyst
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Embryo :
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Starts from week 4 through the end of week 8
Major organ systems are structurally formed during this period
Shape of the embryo changes as the organs develop, taking
a more human shape by end of 8th week
Major events of the embryogenic period include :
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folding of the embryo
-
organogenesis
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Fetus :
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Begins from start of the 9th weeks and extends
through the duration of the pregnancy
Includes the appearance of vernix caseosa,lanugo and scalp
hair
Eyelids open at about 24 to 26 weeks
Closer to term, subcutaneous fat is deposited, giving the
skin smooth,firm,plump appearance and texture
The last part of the fetal period provides preparation for
transition to the extrauterine environment.
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