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  • 人类胎儿 -- -- 高级

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    What characterizes this fetus as human?
    ::这个胎儿是什么人?

    The human fetus. Notice the details in the face and hands. Compare this to the human embryo . The amount of growth and is truly remarkable.
    ::人类胎儿。 注意面部和手部的细节。 把这个与人类胚胎相比。 成长的程度和真正的非凡。

    Growth and Development of the Fetus
    ::胎儿的增长和发展

    From week 8 until birth, the developing individual is referred to as a fetus. In humans, birth typically occurs 38 weeks after , so the fetal period lasts about 30 weeks. During this time, the organs that formed during the embryonic period go through further development.
    ::从第8周到出生,发育中的个人被称为胎儿。在人类中,出生通常发生在38周之后,因此胎儿期大约为30周。在此期间,胚胎期形成的器官经过进一步发育。

    Weeks 8 to 15
    ::8至15周

    During the fetus’s early weeks, reproductive organs develop along either male or female lines. The liver starts producing red blood cells , and tooth buds appear. The fetus becomes more human in appearance, with well-formed facial features. The eyelids form, but remain closed until later in fetal development. The and develop, and the fetus is very active. It can make a fist and move its arms and legs. It also hiccups, stretches, and yawns. The first measurable brain activity occurs around the 12th week. By the end of the 15th week, the fetus is about 15 centimeters long.
    ::在胎儿早期的几周里,生殖器官沿着男性或女性的界线发展。肝脏开始产生红细胞,牙齿芽出现。 胎儿的外表更加人性化,面部特征也更加美化。眼皮形成,但在胎儿发育阶段一直闭着。眼皮和胎儿非常活跃。它可以握拳,移动手臂和腿部。它也可以打嗝、伸展和打哈欠。第一个可以测量的大脑活动发生在12周左右。 到15周结束时,胎儿大约15厘米长。

    Weeks 16 to 26
    ::第16至26周

    A fetus at 23 weeks after fertilization is shown in Figure  . At this stage, the brain is developing rapidly, and it starts to take control of some body functions. The alveoli (air sacs) in the lungs also develop, making gas exchange possible, although the lungs are still immature. Most of the internal components of the and ears form and develop at this time. There is more muscle development as well, and the fetus is more active than ever. The mother usually starts to feel fetal movement during this stage.
    ::图中显示受精后23周的胎儿。在现阶段,大脑正在迅速发育,开始控制某些身体功能。肺部的肺部气囊也在发育,使气体交换成为可能,尽管肺部仍然不成熟。大部分内部成分和耳朵形态目前都在发育。肌肉发育也越来越多,胎儿比以往更加活跃。母亲通常在现阶段开始感觉胎儿运动。

    Fetus at 23 weeks after fertilization.
    A fetus at 23 weeks after fertilization.

    Fine hair called lanugo grows and covers the fetus’s body by the end of this stage. Eyebrows, eyelashes, and nails also appear, and the eyelids begin to open and close. By the end of week 26, the fetus is about 38 centimeters long and weighs about 1.2 kilograms.
    ::这一阶段结束时,被称为拉努戈的美发长长,覆盖胎儿的身体。 眼眉、睫毛和钉子也出现,眼皮开始开闭。 到26周结束时,胎儿长约38厘米,体重约1.2公斤。

    Weeks 27 to 38
    ::27至38周

    During the final weeks of growth and development, the amount of body fat rapidly increases. Bones develop fully, although they are still soft and pliable. Most of the lanugo disappears, and head hair becomes coarser and thicker. Fingernails grow beyond the ends of the fingertips. In the brain, connections form that allow the input of sensations. Starting around week 30, the brain is continuously active. By the 38th week, the fetus is fully developed and ready to be born. A 38-week fetus normally ranges from 36 to 51 centimeters in length and weighs between 2.7 and 4.6 kilograms. A 38-week-old fetus is shown in Figure .
    ::在最后几周的成长和发育期间,身体脂肪的含量迅速增加。 Bones 完全发育, 尽管它们仍然柔软和可食用。 大部分的乳酪会消失, 头发会变粗和厚。 指甲会长到指尖的尽头。 在大脑中, 连接形式允许感官输入。 从大约第30周开始, 大脑会持续活跃。 到第38周, 胎儿已经完全发育并准备出生。 38周的胎儿的长度通常在36至51厘米之间, 体重在2.7到4.6公斤之间。 图中显示的是38周的胎儿。

    A fetus at 38 weeks with placenta, amniotic sac, and umbilical cord.
    A fetus at 38 weeks with placenta, amniotic sac, and umbilical cord.

    Sometimes fetuses are born earlier than 38 weeks. After 35 weeks, the fetus is considered “full-term,” which means that it is developed enough for life outside the mother. Fetuses born before 35 weeks are likely to have health problems due to their immaturity, although many are able to survive with medical help. The less time a fetus spends developing in the uterus before it is born, the less likely it is to survive after birth. Fetuses born before 25 weeks rarely survive.
    ::有时胎儿出生时间早于38周,35周后,胎儿被视为“完全的”,这意味着胎儿的发育足以在母亲之外生活。 35周前出生的胎儿可能因其不成熟而有健康问题,尽管许多人能够依靠医疗帮助生存。胎儿出生前在子宫发育的时间越少,出生后存活的可能性就越小。25周前出生的胎儿很少存活下来。

    Fetus at 18 weeks after fertilization.
    Fetal Development (Weeks 9-38). Organ development is completed and body size increases dramatically during weeks 9-38.

    Summary
    ::摘要

    • The fetal stage begins about 8 weeks after fertilization and continues until birth.
      ::胎儿阶段在受孕后大约8周开始,并持续到出生为止。
    • During the fetus’s early weeks, reproductive organs develop along either male or female lines.
      ::在胎儿早期的几周里,生殖器官按照男性或女性的顺序发展。
    • By the 38th week, the fetus is fully developed and ready to be born.
      ::到第38周 胎儿完全发育成熟 准备出生

    Review
    ::回顾

    1. When does the fetus start developing reproductive organs?
      ::胎儿什么时候开始发展生殖器官?
    2. When does the brain of the fetus become continuously active?
      ::胎儿的大脑何时开始持续活跃?
    3. What does it mean for a fetus to be "full-term."
      ::胎儿是"完全的"是什么意思?