口腔里有酸味怎么回事:子宫日记（3）

In the womb 3

       Soon after the fertilization, the egg begins its journey, traveling along the fallopian tube(输卵管) toward the safety of the uterus(子宫). About a day after fertilization, the egg divides for the first time. Every cell in the body will need its own copy of the genetic blueprint. The chromosomes(染色体) reproduce first, making an identical copy of the entire genetic code. When the two sets of chromosomes part, the nucleus splits in two and the cell divides.

        授精之后，受精卵就开始了旅程，它要穿过输卵管一直到达安全的子宫。大概在授精一天后，受精卵开始第一次分裂。婴儿身体里每个细胞都需要复制自己的遗传物质。染色体首先进行复制，得到一份一模一样的完整的遗传密码。当完全一样的两组染色体分离后，细胞核也分裂为两个，一个细胞就分裂成两个细胞。

      This process of division continues as the clump of cells travels down the fallopian tube. After four or five days, the tiny ball called the blastocyst(胚泡) has grown to around 100 cells, and it begin to separate into two sets. The outer ring of cells will become the placenta(胎盘)—the life support system—while the inner circle will become the embryo itself.

受精卵在输卵管中前进时，细胞分裂一直在进行，这时的受精卵称为胚泡。大概四五天后，已经含有大约100个细胞的胚泡开始分成两部分。外层的细胞将发展为胎盘——这是未来生命的支持系统，而内层的细胞将发展为胚胎。

       At this stage, the inner cells are known as stem cells. Stem cells have the remarkable capacity to turn into any one of over 200 different types of cells, and they can grow to become any part of the body. After seven days, the blastocyst reaches the end of the fallopian tube and arrives in the uterus—a haven(港口) for the next nine months.

内层细胞医学上叫做干细胞。干细胞具有惊人的生长能力，它们可以变成200多种不同形态的细胞，而这些细胞可以组成身体的任一部分。七天之后，胚泡到达了输卵管的尽头，进入了子宫——它未来九个月居住的港湾。

        More than a week has passed since conception, but until she misses a menstrual(月经的) cycle, the mother may not even realize she is pregnant. Over the course of the first trimester or first three months, the single egg will begin to transform itself into a fully formed baby. But all the features of the human body—limbs, nerves, organs, muscles—will be mapped out in the fragile first weeks.

        授精已经一周多了，但是母亲不会意识到她已经怀孕，除非她发现自己停了月经。在怀孕的头三个月里，受精卵将不断分裂成一个形态完整的胎儿，但是胎儿未来所有的身体组织形态——四肢、神经、器官、肌肉，都是在怀孕早期胚胎最最脆弱的几星期里决定的。

        The embryo is now starting to take shape. During the third week, the embryonic ball of cells, no bigger than a pinhead, folds in on itself to form a long tube. The top of the tube is growing into the head, and the trunk of the body stretches down below. The head doesn’t look much like a head yet. But at day 15, nerve cells begin to form in what will become the brain, as well as in the spinal column(脊柱), which is exposed and totally unprotected by either skin or bone.

       胚胎现在开始成形。第三周，胚泡球的大小和绣花针尖差不多。它开始变成一根长长的管子，管子的顶端将成会为胎儿的脑袋，余下部分将成为她的身体，虽然脑袋现在看起来一点也不像。在第15天，神经细胞开始成形，它们将发展成胎儿的大脑和脊柱。这个时候它们是完全暴露的，没有皮肤也没有骨头来保护它们。

        For now, the mother is most likely unaware that her body is creating a protected world—one that can successfully sustain a pregnancy. Yet drastic changes immediately begin to sweep through her system. Her blood volume may increase by up to 50% to cope with the extra demand for oxygen from the parasitic(寄生的) growth in her womb. Once the embryo embeds itself in the uterus, it starts to draw from the mother’s bloodstream all that it needs to grow.

这个时候，母亲可能还没有意识到她的身体需要被好好保护，来度过漫长的十月怀胎。她的身体开始发生剧烈变化，血管可能比原来扩展一半，以运送子宫里的生命所需要的氧气。一旦胚胎在子宫里安了家，它就开始从母亲的血液中吸收营养。

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