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蛋壳里的动物怎么获得氧气?

How Birds Get Oxygen Inside Their Eggs

看看这个孵卵器的里面
Look inside this incubator.
这些蛋产于21天前
These eggs were laid 21 days ago
而这枚就要孵化了
and this one is just about to hatch.
如果你仔细听 你就能听到
If you listen you can hear the chick pecking
鸡仔在里头啄壳的声音
at the inside of its shell.
很快它将破壳而出 呼吸第一口新鲜空气
Soon it will break through and take its first breath of fresh air.
包括我们在内的许多生物的第一次呼吸
It’s a dramatic moment that first breath –
是多么令人激动的时刻
one shared by so many creatures including us
但是等一下 想想这种情况
But hold on, think about this:
当你在子宫里
When you were in the womb
你通过脐带从你母亲那里获得氧气
you got oxygen from your motherthrough your umbilical cord.
但在过去的21天中 这只鸡仔和它母亲切断联系
But for the last 21 days this chick has been cut off from its mother –
被封闭在蛋壳里
sealed inside an egg.
那么它是如何获得氧气的呢?
So how does it get oxygen?
《NPR浣熊》主持人:亚当·科尔
一个鸡蛋看起来像一个完美的自给系统
An egg seems like a perfectly self-contained system.
蛋黄和蛋清包含鸡仔生长所需的
The yolk and the white contain all the nutrients you need
所有营养
to build a baby chick.
与人类婴儿一样 构造的过程需要氧气
As with a human baby,all this construction requires oxygen
而这在蛋中是没有的
and that’s the one thing that isn’t storedinside the egg.
所以氧气从哪儿来?
So where does it come from?
我们来看看这个
Well take a look at this.
当你把蛋壳放大一千倍
When you magnify an egg’s shell a thousand times
你会发现蛋壳是由
you can see the calcium carbonate
碳酸钙晶体组成
crystals that make up the shell
并且到处都有细小的缝隙
and here and there — tiny holes.
直径大约千分之一英寸
One thousandth of an inch across.
这些微小的孔能让外界的空气渗入
And these tiny holes let outside air filter in.
所以氧气能够穿过蛋壳
So oxygen can pass through the shell,
但是蛋里头生长的鸡仔还未发育出健全的肺
but the chick growing inside doesn’t have working lungs yet.
氧气是如何进入它的血流的呢?
How does it get that oxygen into its bloodstream? Well,
蛋被产下几天以后
a few days after an egg is laid
神奇的事情发生了
something amazing happens.
当你拿起一枚已经受精的蛋
When you hold a fertilized egg up in front
放在亮光前 你会发现
of a bright light, you can see it:
一个由纤细血管形成的网络
a delicate network of blood vessels that grows
从胚胎的腹部长了出来
out of the embryo’s abdomen
紧贴在蛋壳内的一层薄膜上
and presses up against a membranejust inside the shell.
空气中的氧气
Oxygen from the air comes in
通过蛋壳内的小孔进入
through the tiny holes in the shell
然后渗透进胚胎的血液内
then diffuses into the embryo’s blood.
同时 成长中的鸡仔会排出二氧化碳
And the growing chick gets rid of carbon dioxide at the same time.
这看起来和你在子宫生活的时候
It all looks remarkably similar to
非常相似
your early days in the womb
有卵黄囊 至少一开始是这样
There was a yolk sac, at least at first,
还有血管网
and a network of blood vessels growing out from
从你现在肚脐的位置长出
the place where your belly button now is.
但你的血管并不是紧贴蛋壳边缘
But instead of pressing up against the edge of a shell
而是紧贴子宫壁
your blood vessels reached the wall of the womb
并与一层外膜连接在一起 形成了胎盘
where they joined with an outer membrane toform the placenta.
氧气经过胎盘 从你的母亲的血渗透到你的血
In the placenta, oxygen from your mother diffusedinto your bloodstream.
这就是鸟类和爬行类动物的蛋
It really is an exact mirror of what’s going
发生情况的真实写照
on in the eggs of birds and reptiles.
与此同时 肺也发育了
While all this is happening, lungs are developing.
我们人类出生以后才用肺呼吸
We humans don’t fill those lungs with air until after we’re born.
但是鸡仔却先行一步
But chicks get a head start.
那是因为氧气在进入蛋壳的同时
That’s because the whole time oxygen is coming in through the shell,
水分也在慢慢地蒸发
moisture is slowly evaporating out.
这就逐步形成了一个充满空气的空间
That creates an empty space that graduallyfills with air.
鸡仔在准备破壳前的一天左右
A day or so before the chick is ready to hatch,
它开始移动
it starts to move.
它啄破气囊使肺充满空气
It punctures that air pocket and fills its lungs.
这样就使得它有足够的氧气破蛋而出
It then has just enough oxygen to battle out of the egg
并且吸到第一口新鲜空气
and take its first breath of fresh air.
这里是《NPR浣熊》 国家电台科学节目
This is Skunk Bear, NPR’s science show
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Please subscribe to our channel and check out our other videos!

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视频概述

蛋壳里的动物是怎么获得氧气孵化的?通过本视频,你将全面了解到卵生动物孵化前的氧气获取途径。

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翻译译者

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视频来源

https://www.youtube.com/watch?v=w-M33PtwtM4

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