章节大纲

  • 常规

    全部折叠 展开全部

  • 化肥化、裂变和植入 -- -- 高级

    lesson content

    How far does a have to swim?
    ::要游多远才能游多远?

    Sperm swimming to an egg . If fertilization occurs, the egg will have all the "instructions" to grow into a new organism . That one will become two, then four, then eight, then sixteen, and on and on and on. And after about 9 months, that one cell will have become a new baby. But it all starts with the sperm swimming to the egg. A sperm cell is about two thousandths of an inch long. And although they are small, they can swim roughly 8 inches in an hour. To reach an egg, they will ultimately have to swim around 192,000 times their own length.
    ::精子游泳到蛋中。 如果施肥发生, 卵子将拥有所有“ 试验” 来成长为新生物。 一种会变成2, 4, 8, 16, 并且持续。 大约9个月后, 一个细胞会变成一个新的婴儿。 但是从精子游到蛋中开始。 精子细胞大约是一英寸的两千分之一长。 尽管它们很小, 它们可以在一小时内游8英寸。 要达到一个蛋, 它们最终必须游到大约19.2万倍的长度。

    Fertilization, Cleavage, and Implantation
    ::化肥、裂变和植树种植

    begins when an egg is fertilized by a sperm and implants in the uterus . Following these events, the remainder of growth and before birth is divided into two main stages. The first stage is the embryonic stage, which lasts about two months. This is followed by the fetal stage, which lasts for another seven months until birth.
    ::当卵子被精子和子宫植入后,卵子开始受精时,继这些事件之后,发育的剩余部分和出生前可分为两个主要阶段。第一个阶段是胚胎阶段,大约为期两个月。接下来是胎儿阶段,再持续7个月直到出生。

    Fertilization, Cleavage, and Implantation
    ::化肥、裂变和植树种植

    A day or two after an ovary releases an egg, the egg may unite with a sperm. However, before it becomes an embryo , it must go through other processes. These processes include cleavage and implantation .
    ::卵卵释放卵后一两天,卵可能与精子结合。然而,在胚胎发育之前,它必须经过其他过程。这些过程包括割裂和植入。

    Fertilization
    ::化肥化

    Fertilization is the union of a sperm and an egg. Recall that a sperm is a male gamete , and an egg is a female gamete. Each gamete is a haploid cell. When the two cells unite during fertilization, they form a diploid cell called a zygote .
    ::授精是精子和蛋的结合。 提醒人们,精子是男性的游戏,蛋是女性的游戏。 每个游戏都是一个杂交细胞。 当两个细胞在受精过程中联合起来时,它们形成一个叫做zygote的浸泡细胞。

    Fertilization generally occurs in a Fallopian tube . After sperm are deposited in the vagina during sexual intercourse, they “swim” through the cervix and uterus and into a Fallopian tube. Although millions of sperm are deposited, only a few hundred are likely to reach the egg. A sperm about to penetrate an egg is shown in  Figure . When a sperm finally breaks through the egg’s , it sets off a reaction that prevents other sperm from entering. The entry of the sperm also triggers the egg to complete the second meiotic division that began before ovulation .
    ::精子在性交期间沉入阴道后,会通过子宫和子宫“游动”进入法罗管。尽管有数百万精子沉积,但只有几百个精子可能到达卵子。图中显示的是即将进入卵子的精子。当精子最终破解卵子时,会引发一种阻止其他精子进入的反应。精子的进入也会触发卵子完成排卵前开始的第二个温和分解。

    Human sperm and egg.

    Human sperm and egg.
    ::人类精子和蛋

    After the sperm penetrates the egg, its tail falls off and its fuses with the nucleus of the egg. The resulting zygote contains all the needed for a new individual. Half the chromosomes are from the egg, and half are from the sperm.
    ::精子渗入卵子后, 尾巴掉下来, 与卵子核的导火线。 由此产生的zygote 包含了新个体所需的全部。 一半的染色体来自卵, 一半来自精子 。

    Cleavage
    ::解裂

    The zygote spends the next few days traveling down the Fallopian tube. As it travels, it divides by several times to form a ball of cells called a morula . The cell divisions, which are called cleavage, increase the number of cells but not their overall size. More cell divisions occur, and soon a fluid-filled cavity forms inside the ball of cells. At this stage, the ball of cells is called a blastocyst . The process of blastocyst formation is shown in  Figure . Cleavage serves two important functions in early development. The process creates a multicellular embryo. It is also an organizing process that partitions the embryo into developmental regions. The cytoplasm of the zygote contains many chemicals that regulate . These chemicals are partitioned during cleavage, and they later activate the genes necessary to form specific parts of the body.
    ::zygote在接下来的几天里穿梭于Fallopian 管线下。 当它行走时, 它会分几次, 形成一个叫Morula的细胞球。 细胞分裂, 叫做裂痕, 增加细胞数量, 但不增加其总体大小 。 更多的细胞分裂会发生, 并且很快在细胞球内出现一个液体填充的洞穴形式 。 在这个阶段, 细胞的球被称为爆破体体体。 爆炸体形成过程在图中显示。 裂变过程在早期发育中有两个重要功能 。 这个过程创造了一个多细胞胚胎。 它也是一个组织过程, 将胚胎分割到发育区。 zygote的细胞系统含有许多调节的化学物质。 这些化学物质在裂变过程中被分割, 然后它们会激活形成身体特定部分所需的基因 。

    lesson content

    The morula (1) continues to undergo cell divisions. As it does, cells start to migrate into separate layers and a cavity starts to develop inside the ball of cells. When cells have migrated into distinct layers, the organism is called a blastocyst (2).
    ::morula (1) 继续接受细胞分解。 和它一样, 细胞开始迁移到不同的层中, 洞穴开始在细胞球中发育。 当细胞迁移到不同的层中时, 有机体被称为爆炸性(2) 。

    The cells of the blastocyst form an inner and an outer cell layer. This is apparent in  Figure . The inner layer of cells is called the embryoblast . This layer of cells will soon develop into an embryo. The outer layer of cells is called the trophoblast . This layer will develop into other structures including the placenta .
    ::调色板的细胞构成内部和外部细胞层。图中可见这一点。细胞的内部层称为胚胎爆裂。这个细胞层很快会发展成胚胎。外部细胞层称为后座体。这个层将发展成其他结构,包括胎盘。

    lesson content

    The blastocyst consists of an outer layer of cells called the trophoblast, a fluid-filled cavity, and an inner cell mass called the embryoblast.
    ::爆炸层由外层细胞组成,外层细胞称为营养质球,一个装满液体的洞穴,内部细胞质量则称为胚胎爆裂。

    Implantation
    ::植 植

    The blastocyst continues the trip down the Fallopian tube and reaches the uterus about four or five days after fertilization. When the outer cells of the blastocyst contact cells lining the uterus, the blastocyst embeds in the lining. The process of embedding is called implantation. It generally occurs about a week after fertilization. Once implantation occurs, the blastocyst is called an embryo.
    ::喷雾器继续沿着Fallopian管进行,并在受精后四、五天左右到达子宫。当喷雾器接触细胞的外细胞在子宫内嵌入时,喷雾器嵌入衬里。嵌入过程称为植入过程。通常在施精后一周左右发生。一旦植入,喷雾器就称为胚胎。

      

     

    Summary
    ::摘要

    • Before an ovum becomes an embryo, it must undergo fertilization, cleavage, and implantation.
      ::卵巢在胚胎形成之前 必须接受授精、分裂和植入
    • Fertilization is the union of a sperm and an egg to form a zygote, which is a diploid cell.
      ::肥化是一种精子和蛋的结合 形成一个zygote, 这是一种浸泡细胞。
    • Cleavage serves two main purposes: it forms a multicellular embryo and organizes the embryo into developmental regions.
      ::裂变主要有两个目的:形成多细胞胚胎,将胚胎组织成发育区。
    • When the outer cells of the blastocyst contact cells lining the uterus, the blastocyst embeds in the lining, a process called implanation.
      ::当爆炸性接触细胞的外部细胞 连接子宫的外部细胞, 爆炸性嵌入在衬衬里, 一个叫“插入”的过程。

    Review
    ::回顾

    1. Where does fertilization occur?
      ::肥化在哪里发生?
    2. How does the egg prevent itself from receiving more than one set of genes?
      ::蛋是如何防止自己接受不止一组基因的?
    3. What two functions does the process of cleavage serve?
      ::分裂过程起到什么两种作用?
    4. What does the trophoblast become?
      ::月球变成什么样了?
    5. When does implantation usually occur?
      ::植入通常何时发生?