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At the climax of sexual intercourse
hundreds of millions of sperms are propelled into the
vagina by the man. Of these 20 to 500 million sperm that
are released, very few ever make it as far as the
uterus, some being destroyed by the woman's immune
system and others simply dying from exhaustion.
Travelling about 10cm in half an hour, the remaining
sperm will make their way up to the cervical opening,
where it is possible for them to remain alive and
healthy for up to 48 hours, as they wait for the
cervical mucus plug to offer a favourable condition for
them to be able to pass through the cervical opening,
and make their way into the Fallopian tube.
Provided there is an egg waiting to be fertilised, the
surviving sperm, will form a cluster around it, until
one manages to break through the porous sheath of
nutrient cells that surround the egg. This is achieved
by dissolving the outer layer material, by means of
chemical reactions containing elements from the sperm
cell and Fallopian tube. The contributions from the
sperm cell to this process, would be the shedding of
part of the sperm cell head, which takes place when the
sperm cell enters the genital tract. The penetration in
this case is also aided by the sperm cell's own physical
activity. Once this has been effectively achieved, and
one sperm cell has penetrated the outer coating of the
egg a remarkable change to the egg now takes place,
whereby, chemicals from the interior of the egg are
released to the coating, so preventing all other sperm
from entering.
Once the sperm and egg cell have fused, a series of
divisions will begin, with each early cell division
taking approximately 12 hours. Therefore a two-cell
embryo would have formed after a 24 hour period, a
four-cell embryo by 36 hours, a 16-cell embryo by about
three days, and so on. These clusters will slowly move
down the Fallopian tube, and on reaching the uterus
would have developed to about the 8 to 16-cell stage.
On reaching the uterus the cluster of cells search for a
site to implant in the endometrium (nutritive lining of
the uterus), this would take around three days to occur.
During this time, the embryo undergoes further changes,
and at this stage will be referred to as a blastocyst.
It will now contain an outer layer of cells which will
in due course form the placenta and the membrane which
will surround the baby; fluid destined to protect and
cushion the foetus, and an inner batch of cells which
will form the baby's organs.
Within ten days of ovulation, the blastocyst will now
implant itself into the endometrium, where it will
continue the miraculous growth that will result in "The
Miracle of Life".
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