Section outline

  • General

    Collapse all Expand all

  • 人类Embryo - 高级

    lesson content

    At one time, did we all really look alike?
    ::有一次,我们都长得真像吗?

    We all start as a single and soon grow into an embryo . Notice the remarkable details beginning to form. The , backbone , and limb buds are obvious. Think about the amazing complexity that must be going on inside the embryo and the tremendous amount of growth and still to come. So, yes, at one time we all looked similar.
    ::我们都从一个单一的胚胎开始,并很快成长为胚胎。注意到这些惊人的细节开始形成。骨干和肢体芽是显而易见的。想想胚胎中必须经历的惊人的复杂性,以及巨大的成长量和未来的发展。所以,是的,我们一度看起来都相似。

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

    An embryo is a developing human being between the time of implantation and the first eight weeks after . During this time, the embryo grows in size and undergoes three processes: gastrulation, differentiation , and organogenesis.
    ::胚胎是在植入时间到植入后头8周之间发育中的人。 在这一时期,胚胎的体积在成长过程中经历了三个过程:轮廓、区别和有机产生。

    Gastrulation
    ::加注

    Gastrulation is the development of different layers of cells in the embryo. It generally occurs during the second week after fertilization. During gastrulation, cells of the embryo migrate to form three distinct cell layers: the ectoderm , mesoderm , and endoderm . These layers are shown in Figure . Each layer will eventually develop into certain types of tissues and cells in the body.
    ::胚胎中不同层细胞的生长是胚胎中不同层细胞的生长过程,通常发生在受精后第二周,在受精期间,胚胎的细胞会迁移成三个不同的细胞层:乳腺、中度和内温。图中显示了这些层。每一层最终会发展成身体中某些类型的组织和细胞。

    • Ectoderm —Forms tissues that cover the outer body; it develops into cells such as nerves , skin, hair, and nails.
      ::Ectoderm - 覆盖外体的表格组织;它发展成神经、皮肤、毛发和钉子等细胞。
    • Mesoderm —Forms tissues that provide movement and support; it develops into cells such as , , teeth, and .
      ::用于提供移动和支持的模型组织;它发展成细胞,例如,......、牙齿和......。
    • Endoderm —Forms tissues involved in digestion and ; it develops into cells such as lungs , liver , pancreas , and gall bladder .
      ::内脏 -- -- 与消化有关的形式组织;它发展成肺、肝、胰腺和胆囊等细胞。

    lesson content

    The three cell layers of the embryo develop into different types of cells. For example, the ectoderm develops into skin cells, the mesoderm into muscle cells, and the endoderm into lung cells.
    ::胚胎的三个细胞层发展成不同类型的细胞,例如,乳腺发展成皮肤细胞,中间细胞发展成肌肉细胞,内脏细胞发展成肺细胞。

    Differentiation and Organogenesis
    ::差异和有机起源

    During the third week after fertilization, the embryo begins to undergo cellular differentiation. Differentiation is the process by which unspecialized cells become specialized into one of the many different types of cells that make up the body. During differentiation, certain genes are turned on, or activated, while other genes are switched off, or inactivated. As a result of this process, cells develop specific structures and abilities that suit them for their specialized roles in the body. Several examples of specialized cells are shown in  Figure , along with the cell layers from which they develop.
    ::胚胎在受孕后第三周开始接受细胞差异化; 差异化是非专门化细胞专门化成构成身体的多种不同类型细胞之一的过程; 在区别化过程中,某些基因被打开或激活,而其他基因被关闭或失去作用; 由于这个过程,细胞发展出适合其在身体中特殊作用的具体结构和能力; 图中列出了专门化细胞的若干例子,以及它们所发展的细胞层。

    Differentiation of cells leads to the development of specific organs within the three cell layers. This is called organogenesis. All the major organs begin to form during the remaining weeks of embryonic development. A few of the developments that occur in weeks 4 through 8 are listed in Figure  .
    ::细胞差异导致三个细胞层中特定器官的发育,这称为有机产生,所有主要器官在胚胎发育的剩余几周内开始形成,图中列出了第4至第8周中出现的一些发展动态。

    lesson content

    Cellular differentiation occurs in the 3-week-old embryo.
    ::3周大的胚胎存在细胞差异。

    Embryonic Development During Weeks 4-8
    ::4-8周期间的胸腺发育

    lesson content

    Embryonic Development (Weeks 4–8). Most organs develop in the embryo during weeks 4 through 8. If the embryo is exposed to toxins during this period, the effects are likely to be very damaging. Can you explain why? (Note: the drawings of the embryos are not to scale.)
    ::细胞发育(Weeks 4-8) 。 大部分器官在4周到8周期间在胚胎中发育。 如果胚胎在此期间暴露在毒素之下,那么其影响很可能非常有害。 你能解释原因吗? (注:胚胎的图画不会缩放。 )

    As the embryo develops, it also grows in size. By the eighth week of development, the embryo is about 30 millimeters long. It may also have begun to move. 
    ::随着胚胎的发育,胚胎的体积也在扩大,到发育的第八周,胚胎的长度约为30毫米,也可能已经开始移动。

      

     

    Summary
    ::摘要

    • An embryo is a developing human being between the time of implantation and the first eight weeks after fertilization.
      ::胚胎是从植入到授精后头8周之间发育中的人类。
    • During gastrulation, cells of the embryo migrate to form three distinct cell layers: the ectoderm, mesoderm, and endoderm. Each layer will eventually develop into certain types of tissues and cells in the body.
      ::胚胎细胞在凝固过程中会迁移成三个不同的细胞层:电离子、中子和内基。每个细胞层最终会发展成身体中某些类型的组织和细胞。
    • During differentiation, certain genes are turned on, or activated, while other genes are switched off, or inactivated. As a result of this process, cells develop specific structures and abilities that suit them for their specialized roles in the body.
      ::在差异期间,某些基因被打开或激活,而其他基因被关闭或停止活动。 由于这一过程,细胞发展出适合其在身体中特殊作用的具体结构和能力。

    Review
    ::回顾

    1. How many layers are formed during gastrulation?
      ::瞄准时有多少层形成?
    2. What tissues and cells does the mesoderm develop into?
      ::中位值发展成什么组织和细胞?
    3. When do the major organs of the body form?
      ::人体的主要机关何时形成?
    4. When do the lungs start to develop?
      ::肺部什么时候开始发育?