化肥化

How far does a sperm have to swim?
::精子要游泳多远?

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 they have to swim around 192,000 times their own length.
::游泳到鸡蛋中。 如果施肥发生, 鸡蛋将拥有所有“ 实验” 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。 但是从精子游泳到蛋开始, 精子细胞大约是1英寸的二千分之一长。 虽然它们小, 却能在1小时内游8英寸。 要达到一个蛋, 它们最终必须游大约19.2万倍的时间。

Cleavage and Implantation
::清除和植入

A day or two after an ovary releases an egg, the egg may unite with a sperm. Sperm are deposited in the vagina during sexual intercourse. They propel themselves through the uterus and enter a fallopian tube . This is where fertilization usually takes place.
::卵卵释放出卵后一两天,卵可能与精子结合,在性交期间,精液沉入阴道,它们通过子宫跳跃,进入输卵管,这是施肥通常发生的地方。

When a sperm penetrates the egg, it triggers the egg to complete . The sperm also undergoes changes. Its tail falls off, and its fuses with the nucleus of the egg. The resulting cell, called a zygote , contains all the needed for a new human organism. Half the chromosomes come from the egg and half from the sperm.
::当精子渗入蛋中时,它会触发卵的完整。精子也会发生变化。它的尾部会掉下来,它的保险丝会与卵子核发生联系。由此产生的细胞叫做zygote,包含新的人类生物所需的一切。染色体的一半来自蛋,一半来自精子。

Morula and Blastocyst Stages
::摩鲁拉和紫细胞系统阶段

The zygote spends the next few days traveling down the fallopian tube toward the uterus, where it will take up residence. As it travels, it divides by several times to form a ball of cells called a morula . The cell divisions are called cleavage . They increase the number of cells but not the overall size of the new organism. As more cell divisions occur, a fluid-filled cavity forms inside the ball of cells. At this stage, the ball of cells is called a blastocyst .
::zygote在接下来的几天里会沿着输卵管向子宫走去, 它会在那里居住。 当它行走时, 它会以数倍的间隔来形成一个细胞球, 叫做摩鲁拉。 细胞分裂被称为裂变。 它们会增加细胞数量, 但没有增加新生物的整体大小 。 随着细胞分裂的增加, 细胞球内会有一个充满液体的洞穴形式 。 在目前阶段, 细胞球会被称为爆炸性球 。

The cells of the blastocyst form an inner cell mass and an outer cell layer, as shown in Figure . The inner cell mass is called the embryoblast . These cells will soon develop into an embryo . The outer cell layer is called the trophoblast . These cells will develop into other structures needed to support and nourish the embryo.
::如图所示,暴风雪的细胞构成内细胞质量和外细胞层。内细胞质量称为胚胎爆裂。这些细胞将很快发展成胚胎。外细胞层称为峰值。这些细胞将发展成支持和培养胚胎所需的其他结构。

Implantation
::植 植

The blastocyst continues down the fallopian tube and reaches the uterus about 4 or 5 days after fertilization. When the outer cells of the blastocyst contact cells of the endometrium lining the uterus, the blastocyst embeds in the endometrium. The process of embedding is called implantation . It generally occurs about a week after fertilization. 
::在受精后四、五天左右到达子宫。当子宫内子宫外接触细胞的外细胞在子宫内嵌入时,在子宫内嵌入。嵌入过程称为植入过程。通常在受精后一周左右发生。

Summary
::摘要

播放段落
• Fertilization is the union of a sperm and egg, resulting in the formation of a zygote.
  ::肥化是一种精子和蛋的结合,形成一个zygote。
播放段落
• The zygote undergoes many cell divisions before it implants in the lining of the uterus.
  ::zygote在植入子宫衬前经历了许多细胞分裂。

Review
::回顾

播放段落
1. What happens during fertilization? Where does it usually take place?
   ::施肥期间会发生什么?通常在哪里发生?
播放段落
2. What is implantation? When does it occur?
   ::什么是植入?
播放段落
3. Describe a morula and blastocyst.
   ::描述一个morula和bombocyst。