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  • General

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  • 怀孕

    Early stages of human embryonic development, illustrating various growth phases without distinct human features.

    Does a growing embryo always look like a tiny human?
    ::一个成长中的胚胎 总是看起来像一个很小的人类吗?

    The above picture shows the very early stages of human development. Notice that, at first, the embryo doesn't look very human! It takes time for the human features to take shape.
    ::以上图示显示了人类发育的最初阶段。 请注意, 胚胎一开始看起来并不很人性! 人类特征的形成需要时间。

    Pregnancy and Childbirth
    ::怀孕和分娩

    While a woman is pregnant, the developing baby may be called an embryo or a fetus . Do these mean the same thing? No, in the very early stages the developing baby is called an embryo, while in the later stages it is called a fetus. When the ball of cells first implants into the uterus , it is called an embryo . The embryo stage lasts until the end of the 8 th week after . After that point until birth, the developing baby is called a fetus .
    ::当妇女怀孕时,发育中的婴儿可以被称为胚胎或胎儿,这是否也意味着同样的事情?不,在早期,发育中的婴儿被称为胚胎,而在后期,它被称为胎儿。当细胞球首先植入子宫时,它被称为胚胎。胚胎阶段持续到出生后第8周结束。此后,发育中的婴儿被称为胎儿。

    Growth and Development of the Embryo
    ::安布里约的增长和发展

    During the embryo stage, the baby grows in size.
    ::在胚胎阶段,婴儿长大了。

    • 3 rd week after fertilization: Cells of different types start to develop. Cells that will form and skin, for example, start to develop at this time.
      ::施肥后第三周:不同种类的细胞开始发育,例如,将形成和皮肤的细胞开始生长。
    • 4 th week after fertilization: Body organs begin to form.
      ::施肥后第4周:身体器官开始形成。
    • 8 th week after fertilization: All the major organs have started to develop.
      ::施肥后第8周:所有主要器官已经开始发展。

    Pictured below are some of the changes that take place during the 4 th and 8 th weeks ( Figure ). Look closely at the two embryos in the figure. Do you think that the older embryo looks more human? Notice that it has arms and legs and lacks a tail. The face has also started to form, and it is much bigger.
    ::以下图示了第四周和第八周发生的一些变化(图 )。仔细看看图中的两个胚胎。 你认为老胚胎更像人类吗?注意它有胳膊和腿,没有尾巴。脸部也开始形成,而且大得多。

    Illustrations of embryos at 4 and 8 weeks showing developmental changes.

    Embryonic Development (Weeks 4–8). Most organs develop in the embryo during weeks four through eight. (Note: the drawings of the embryos are not to scale.)
    ::胚胎发育(Weeks 4-8) 。 大多数器官在四到八周内在胚胎中发育。 (注:胚胎的图画不能缩放。 )

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

    There are also many changes that take place after the embryo becomes a fetus. Some of the differences between them are obvious. For example, the fetus has ears and eyelids. Its fingers and toes are also fully formed. The fetus even has fingernails and toenails. In addition, the reproductive organs have developed to make the baby a male or female. The brain and lungs are also developing quickly. The fetus has started to move around inside the uterus. This is usually when the mother first feels the fetus moving.
    ::在胚胎成为胎儿后也发生了许多变化,其中有一些差异是显而易见的。例如,胎儿有耳朵和眼皮,手指和脚趾也完全形成。胎儿甚至有指甲和脚趾。此外,生殖器官已经发展到使婴儿成为男性或女性。大脑和肺部也正在迅速发育。胎儿开始在子宫内流动。这通常是当母亲开始感觉胎儿动的时候。

    By the 28 th week, the fetus is starting to look much more like a baby. Eyelashes and eyebrows are present. Hair has started to grow on the head. The body of the fetus is also starting to fill out as muscles and bones develop. Babies born after the 28 th week are usually able to survive. However, they need help because their lungs are not yet fully mature. A baby should not be delivered prior to this time, unless absolutely necessary. A baby born prior to week 28 will need considerable medical intervention to survive.
    ::到第28周,胎儿开始看起来更像婴儿。有眉毛和眉毛。头发开始长在头上。胎儿的身体也开始随着肌肉和骨头的发育而填满。第28周之后出生的婴儿通常能够存活下来。但是,他们需要帮助,因为他们的肺还没有完全成熟。在这个时候,除非绝对必要,否则不应该生孩子。第28周之前出生的婴儿需要大量的医疗干预才能生存。

    During the last several weeks of the fetal period, all of the organs become mature. The most obvious change, however, is an increase in body size. The fetus rapidly puts on body fat and gains weight during the last couple of months. By the end of the 38 th week, all of the organs are working, and the fetus is ready to be born. This is when birth normally occurs. A baby born before this time is considered premature.
    ::在胎儿期的最后几个星期,所有器官都成熟了,但最明显的变化是身体体积的增大。胎儿在最后几个月里迅速将脂肪加到身体上,并增加体重。到第38周末,所有器官都在工作,胎儿已经准备好出生。这是正常出生的时候。在这个时候之前出生的婴儿被认为是早产的。

    The Amniotic Sac and Placenta
    ::羊水和柏伦塔

    During pregnancy, other structures also develop inside the mother’s uterus. They are the amniotic sac , placenta , and umbilical cord ( Figure ).
    ::怀孕期间,其他结构也在母亲的子宫内发展。 它们是羊膜囊、胎盘和腹骨(图 ) 。

    A fetus in the amniotic sac, illustrating pregnancy structures and connections.

    Surrounding the fetus is the fluid-filled amniotic sac. The placenta and umbilical cord are also shown here. They provide a connection between the mother’s and fetus’s blood for the transfer of nutrients and gases.
    ::胎盘周围是装满液体的羊水囊。 胎盘和腹骨也在这里显示。 它们提供了母亲和胎儿血液之间的连接,用于营养和气体的转移。

    • The amniotic sac is a membrane that surrounds the fetus. It is filled with water and dissolved substances, known as amniotic fluid. Imagine placing a small plastic toy inside a balloon and then filling the balloon with water. The toy would be cushioned and protected by the water. It would also be able to move freely inside the balloon. The amniotic sac and its fluid are like a water-filled balloon. They cushion and protect the fetus. They also let the fetus move freely inside the uterus.
      ::羊膜囊是一种环绕胎儿的膜膜,充斥着水和溶解物质,称为羊膜液。想象一下把一个小塑料玩具放在气球里,然后把气球装满水。这个玩具可以被水垫和保护。它也可以在气球内自由移动。羊膜囊及其液体就像一个装满水的气球。它们可以让胎儿在子宫内自由移动。
    • The placenta is a spongy mass of . Some of the vessels come from the mother. Some come from the fetus. The placenta is attached to the inside of the mother’s uterus. The fetus is connected to the placenta by a tube called the umbilical cord . The cord contains two arteries and a vein . Substances pass back and forth between the mother’s and fetus’s through the placenta and cord. Oxygen and nutrients pass from the mother to the fetus. Carbon dioxide passes from the fetus to the mother.
      ::胎盘是一种海绵质。有些胎盘来自母亲,有些来自胎儿。胎盘附在母亲的子宫内。胎盘与胎盘相连,通过一个叫作子宫系的管子连接到胎盘。绳子包含两个动脉和血管。母亲和胎儿之间的物质通过胎盘和绳子来回传来。氧气和养分从母亲传到胎儿。二氧化碳从胎儿传到母亲。

    It is important for the mother to eat plenty of nutritious foods during pregnancy. She must take in enough nutrients for the fetus as well as for herself. She needs extra calories , proteins , and lipids . She also needs more vitamins and minerals .
    ::母亲在怀孕期间必须吃大量营养食品,她必须给胎儿和自己足够的营养,她需要额外的卡路里、蛋白质和脂质,她还需要更多的维生素和矿物质。

    In addition to eating well, the mother must avoid substances that could harm the embryo or fetus. These include alcohol, illegal drugs , and some medicines. It is especially important for her to avoid these substances during the first eight weeks after fertilization. This is when all the major organs are forming. Exposure to harmful substances during this time could damage the developing body systems.
    ::除了吃好东西外,母亲必须避免可能伤害胚胎或胎儿的物质,包括酒精、非法药物和某些药物,在施肥后头8周避免这些物质对母亲特别重要,这是所有主要器官形成的时候,在此期间接触有害物质可能会损害发育中的身体系统。

    Childbirth
    ::分娩 分娩

    During childbirth , a baby passes from the uterus, through the vagina , and out of the mother’s body. Childbirth usually starts when the amniotic sac breaks.
    ::在分娩期间,婴儿从子宫、阴道和母亲的身体中通过。 分娩通常在羊膜断裂时开始分娩。

    Then, the muscles of the uterus start contracting. The contractions get stronger and closer together. They may go on for hours. Eventually, the contractions squeeze the baby out of the uterus. Once the baby enters the vagina, the mother starts pushing. She soon pushes the baby through the vagina and out of her body.
    ::然后,子宫的肌肉开始萎缩。 子宫的肌肉开始萎缩。 收缩越来越紧密, 它们可能会持续几个小时。 最后, 收缩会将婴儿挤出子宫。 一旦婴儿进入阴道, 母亲就开始推动。 她很快会把婴儿推入阴道, 并推出她的身体。

    As soon as the baby is born, the umbilical cord is cut. After the cord is cut, the baby can no longer get rid of carbon dioxide through the cord and placenta. As a result, carbon dioxide builds up in the baby’s blood. This triggers the baby to start breathing. The amniotic sac and placenta pass through the vagina and out of the body shortly after the birth of the baby.
    ::婴儿一出生,就切断了腹骨。 断了脊髓后,婴儿再也不能通过脊髓和胎盘清除二氧化碳。 结果,二氧化碳在婴儿血液中积聚。 这促使婴儿开始呼吸。 羊膜和胎盘在婴儿出生后不久通过阴道和身体。

    Summary
    ::摘要

    • A zygote develops into an embryo and then a fetus.
      ::zygote 发展成胚胎 然后胎儿。
    • During pregnancy, the amniotic sac, placenta, and umbilical cord develop inside the mother’s uterus.
      ::怀孕期间,母亲的子宫内有羊膜、胎盘和腹膜带。

    Explore More
    ::探索更多

    Use the resource below (printable version) to answer the questions that follow.
    ::使用以下资源(可打印版本)回答下列问题。

    • Anatomy of Childbirth at
      ::分娩解剖
    1. What hormone does the mother secrete at the start of labor? What is the affect of this hormone
      ::母母在劳动开始时会分泌什么荷尔蒙?这种荷尔蒙的影响是什么?
    2. What signals the start of "active labor"?
      ::什么预示着"活体劳动"的开始?
    3. What happens at the "pushing stage" of childbirth?
      ::在分娩的"推推阶段"会发生什么?
    4. What is the leading cause of maternal death in developing countries?
      ::发展中国家产妇死亡的主要原因是什么?

    Review
    ::回顾

    1. What's the difference between an embryo and a fetus?
      ::胚胎和胎儿有什么区别?
    2. What is the amniotic sac and amniotic fluid? Explain their roles.
      ::羊水和羊水是什么?
    3. What is the placenta and umbilical cord? Explain their roles.
      ::胎盘和腹骨的绳索是什么?
    4. What triggers a baby to start breathing after birth?
      ::是什么促使婴儿出生后开始呼吸?