How mucus keeps us healthy - Katharina Ribbeck

翻译人员: Di SUN 校对人员: Yolanda Zhang

If you've got a cold, mucus is hard to miss.

当你感冒时，肯定躲不开黏液。

But what is it, and what does it do besides making you miserable?

那么黏液究竟是什么？ 除了让你感到难受，它还有什么功能？

Your body produces more than a liter of mucus every day,

你的身体每天产生超过1升的黏液，

and all the wet surfaces of your body that are not covered by skin,

多分布在没有被皮肤覆盖的湿润表面，

like your eyes,

比如眼睛里，

nose,

鼻子里，

mouth,

嘴里，

肺壁，

lungs,

以及胃壁也有一层黏膜。

and stomach get a liberal coating.

That's why they're known as mucus membranes.

所以它们也被称为黏膜。

Mucus plays lots of roles in your body.

黏液在人体中发挥着多种作用。

It keeps delicate tissues from drying out and cracking,

它防止脆弱的组织干裂，

which would expose them to infection.

从而避免组织受感染。

It lubricates your eyes so you can blink.

它滋润了眼球表面，方便眼睛眨动。

It protects your stomach lining from acid.

它防止胃内壁被酸腐蚀。

It neutralizes threats by removing or trapping substances

黏液还通过排除或吸附异物， 减弱一些致病因子

that could make you sick.

对身体的侵袭。

And finally, it houses and keeps your body's trillions of bacterial inhabitants,

另外，黏液中还寄生着几万亿细菌，

your microbiota, under control.

并控制着这些微生物群。

Mucus contains lots of different compounds,

黏液中包含多种化合物，

including proteins, fats, and salts.

包括蛋白质、脂肪和各类盐。

But a key component of mucus versatility is a set of proteins called mucins.

其中一种关键的成分，叫做黏蛋白。

Mucins are the primary large molecules in mucus

黏蛋白是黏液中主要的大分子，

and are essential for giving mucus its slippery feel.

黏液的润滑感多来自于黏蛋白。

黏蛋白是一种糖蛋白，

They belong to a class of proteins called glycoproteins

which are built out of both amino acids and sugars.

是由氨基酸和糖构成的。

In mucin, long chains of sugars are attached to specific amino acids

在黏蛋白中，糖链与蛋白支架上

in the protein backbone.

特定的氨基酸结合。

The hydrophilic sugar chains help mucin dissolve in your body's watery fluids.

亲水性的糖链使黏蛋白在体液中溶解。

Mucus, which is up to 90% water,

正是这些糖链的存在

stays hydrated thanks to these sugar chains.

使得黏液中含有90%以上的水分。

Some of these mucins can interact with other mucin molecules

一些黏蛋白可以和 其他黏蛋白分子结合，

to create a complex network that establishes a barrier

构建一个复杂的保护屏障，

against pathogens and other invaders.

来抵御病原体和其他侵入物。

That's why mucus is the body's first line of defense against foreign objects,

这就是为什么说 黏液是人体的第一道屏障，

like bacteria and dust.

能抵抗细菌和灰尘等的侵入。

It's continuously produced to clear them from the respiratory tract,

呼吸道内壁的黏液不断产生，

like a slimy conveyor belt.

像传送带一样清理吸入的异物。

This keeps bacteria from getting a solid purchase on delicate lung tissue,

这样可以避免细菌感染脆弱的肺组织，

or making it to the blood stream, where they could cause a major infection.

也能防止细菌进入到血液 而引起严重感染。

Many of those harmful bacteria also cause diseases

有害细菌聚集生长成粘滑的

when they cluster into slimy growths called biofilms.

生物膜时，能够致病。

But mucus contains mucins,

但黏液中包含黏蛋白，

antimicrobial peptides,

抗菌肽，

antibodies,

抗体，

and even bacteria-hungry viruses called bacteriophages

还有能吞噬细菌的病毒，叫做噬菌体。

that all work together to prevent biofilms from forming.

这些成分协同作用防止生物膜的生成。

If microbes do become harmful and you get sick,

当微生物导致人体生病时，

the body ramps up mucus production to try to quickly flush out the offenders,

人体会增加黏液的分泌， 将致病体迅速冲出体外，

and the immune system floods your mucus with extra white blood cells.

同时免疫系统也会释放 更多白细胞到黏液中。

In fact, the greenish mucus often associated with infections

实际上，绿色的黏液往往与感染相关，

gets its color from an enzyme produced by those white blood cells.

它的绿色是由白细胞产生的酶释放的。

This multi-pronged approach to bacterial management

这多管齐下的细菌防控系统

is one of the main reasons why we're not sick all the time.

正是我们能够维持健康的主要原因之一。

Even though mucus protects against the infectious bacteria,

尽管黏液保护我们不受细菌感染，

the vast majority of your body's bacterial tenants are not harmful,

你身体中大多数的细菌其实是无害的，

and many are actually beneficial.

甚至很多是对人体有益的。

That's particularly true when they live in mucus,

尤其是那些生长在黏液中的细菌，

where they can perform important functions,

它们在黏液中发挥了很重要的作用，

like synthesizing vitamins,

比如合成维他命，

suppressing harmful inflammation,

消除炎症，

and controlling the growth of more harmful species.

和抑制有害物的生长。

So even though you probably associate mucus with being ill,

虽然我们总把黏液和 生病联系在一起，

it's really helping you stay healthy.

但它其实正在帮助我们维持健康。

Sure, it might seem gross,

黏液看起来的确挺恶心的，

but can you think of any other substance that can lubricate,

但你还知道有其他物质 可以像黏液这样润滑，

keep your body clean,

能保持身体清洁，

fight infection,

能对抗感染，

and domesticate a teeming bacterial population?

还能驯服寄生的细菌群吗？

Nope, just mucus.

没有，只有黏液。