懷孕 |
受精
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受精:只有一個精子穿透卵子的外層。然後,精子的頭和卵子的核融合,形成一個新細胞:受精卵。 Fertilization: Only one sperm cell penetrates the outer layer of the egg cell. The head of the sperm cell and the nucleus of the egg cell then unite and form a new cell: the zygote.
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當卵子從卵巢釋放出來時,它幾乎立刻進入所毗鄰的輸卵管開口端。當她在輸卵管內向子宮移動的時候,繼續成熟,為與精子結合做好準備。數小時內,雖然卵子仍然位於輸卵管的前1/3段,她卻達到了成熟。如果受精將要發生的話,這恰恰是精子應該抵達的時候。精子與卵子能夠結合的全部時間小於24小時。如果沒有結合,卵子會死去和分解。可是,卵子遷移至輸卵管時,可以很好地與性交數天后就已經到達輸卵管並且留守的精子相結合。(已經發現,精子會在性交後於輸卵管內存活達5天。) |
Conception |
Fertilization
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When an egg is released
from one of the ovaries, it almost
immediately enters the open end of the
adjacent Fallopian tube. As it travels
down this tube toward the uterus, it
matures to become ready for the union
with a sperm cell. Within a few hours,
the egg reaches maturity while it is
still in the upper third of the
Fallopian tube. This is the time when
the sperm should arrive if a fertilization
is to occur. The
entire period in which egg and sperm can
unite is less than 24 hours.
If no such union takes place, the egg
dies and disintegrates. However, moving
into the Fallopian tube, the egg may
very well encounter live sperm cells
which have arrived and stayed there
following coitus several days before.
(Sperm cells have been found alive
inside Fallopian tubes up to five days
after coitus.)
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