什么件是铸铝的:子宫日记（4）

In the womb 4

       One of the first organs to form is the heart. Until now, the tiny clump of the heart cells about the size of a poppy seed has been still. But after 22 days a single cell stirs as it jolted(摇晃) to life. This tiny movement sparks a chain reaction and other cells in the cluster pick up the rhythm. Incredibly, they all begin to beat in perfect unison. The new cells divide, dance to the same beat and will grow to form the embryo’s heart. The muscle cells of the heart are preprogrammed to contract. Later on when the nervous system is more developed, the brain will carefully control the rate of contraction, keeping it steadily beating and pumping for the rest of the child’s life.

       第一个形成的器官是心脏。现在暗红色的心肌细胞还是静止的，但是在22天后就会有一个细胞动起来，它开始有了生命。这个细胞的动作也激发了其它心肌细胞的动作，它们开始以和谐一致的节奏跳动。新的心肌细胞产生后，也会以同样的节奏舞动着身体，这样胎儿的心脏就形成了。心肌细胞具备收缩功能是先天决定的。当神经系统发展得更为全面时，大脑就能控制心脏的收缩率，使它在孩子一生中都稳定地跳动。

        If she lives to 75 that will be nearly 3billion heart beats. Without a heart there is no way to deliver the food and oxygen the embryo needs to flourish. Now with the heart pumping, primitive blood cells start to circulate in the fetus(胎儿) through veins no thicker than a hair. The blood cells bring vital supplies of oxygen and nutrients to fuel her phenomenal growth over the next 8 months.

       如果孩子能活到75岁，那么心脏将会跳动近30亿次。没有心脏，就不能输送胚胎生长需要的食物和氧气。有了心脏的跳动，原始的血细胞也开始在 胎儿头发丝一样细的静脉里流动循环，它们将在胚胎今后八个月生长期内提供重要的氧气和营养物质。

        After 4 weeks, the embryo is no bigger than a kidney bean and is growing by about 1/10 of a centimeter everyday. Black dots on her head are the beginnings of eyes. Her miniature single-chambered heart beats 80 times per minute and is getting faster everyday. Emerging buds(芽) along her body will grow into arms and legs. Plates of tissue growing in form four sides create her face. The top section grows down to make her forehead and nose. The cheeks fold in from the sides and join to form her top lip. Even in the adulthood, we bear a clear mark from the scene, the vertical groove(槽) between the mouth and nose called the philtrum(人中). If the sides don’t join up properly the baby will develop a cleft(豁开) palate(上腭) and may need corrective surgery after she is born.

       四周后，胚胎的个头只和一个肾脏的大小差不多，她以每天 0.1厘米的速度生长。她头上那个黑黑的圆点将成为眼睛，已经形成心室的微小心脏每分钟跳动约80次，而且速度会变得越来越快。在她身体上突起来的嫩芽将成为手臂和腿。形成脸的组织同时向四个方向生长，顶部将向下倾斜成为额头和鼻子，脸颊在两侧形成，并慢慢合拢成为她的嘴唇。在成人后，我们还是能看到这一变化的一个明显标志，也就是嘴唇与鼻子之间的凹槽被称为人中的部分。如果两边脸颊没有很好地合拢，那么婴儿的嘴就会豁开，形成唇裂，也就是通常所称的兔唇。婴儿就需要在出生之后进行嘴唇的矫正手术。

       At day 30, even an expert would find it difficult to tell just from looking at it, if this embryo is going to become a human, a pig, or an ape. Just one and a half percent of our genes make us human. We share 98.5 percent of our DNA with chimpanzees(黑猩猩), 3 quarters with dogs, half with fruit flies and a third with daffodils(水仙花).

       三十天的时候，即使是一位医生也很难从外表分清胚胎将来到底是什么动物，它可能是一个人，但也可能是一头猪或者一只大猩猩，因为只有1.5%的基因决定了我们是人类。我们的DNA与黑猩猩的98.5%相同，与狗的四分之三相同，与果蝇的一半相同，与水仙花的三分之一相同。

      For the next few weeks, the embryo will continue to grow according to her own internal genetic blueprint and will become more like a human. The fetus has been growing now for 6 weeks. She is almost an inch long and would fit neatly inside a walnut(胡桃) shell. Just black dots a few days ago , her eyes are now glassy sightless stones with no eyelids set widely apart. Her head is still massive compared to her body. Even at birth, it would be a quarter of her body length. The rest of her body won’t catch up with her head until adolescence.

       在未来的几周里，胚胎将根据她的遗传密码生长，看起来就更像个小人了。胎儿现在已经长了六个星期。她大概有一英寸长，可以很轻易地被塞进一棵胡桃核里。几天前还是黑色圆点的地方，未来的眼睛，像两个看不见东西的玻璃球，没有眼睑。她的脑袋和身体比起来硕大无比。其实即使在出生时，婴儿的脑袋也是身体的四分之一大，身体要直到青春期后才会超过脑袋的比例。

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