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

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

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

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

  • like your eyes, nose, mouth, lungs, and stomach get a liberal coating.

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

  • Mucus plays lots of roles in your body.

  • It keeps delicate tissues from drying out and cracking,

  • which would expose them to infection.

  • It lubricates your eyes so you can blink.

  • It protects your stomach lining from acid.

  • It neutralizes threats by removing or trapping substances that could make you sick.

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

  • your microbiota, under control.

  • Mucus contains lots of different compounds,

  • including proteins, fats, and salts.

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

  • Mucins are the primary large molecules in mucus

  • and are essential for giving mucus its slippery feel.

  • They belong to a class of proteins called glycoproteins

  • which are built out of both amino acids and sugars.

  • In mucin, long chains of sugars are attached to specific amino acids in the protein backbone.

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

  • Mucus, which is up to 90% water,

  • stays hydrated thanks to these sugar chains.

  • Some of these mucins can interact with other mucin molecules

  • to create a complex network that establishes a barrier against pathogens and other invaders.

  • That's why mucus is the body's first line of defense against foreign objects, like bacteria and dust.

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

  • like a slimy conveyor belt.

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

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

  • Many of those harmful bacteria also cause diseases

  • when they cluster into slimy growths called biofilms.

  • But mucus contains mucins, antimicrobial peptides, antibodies,

  • and even bacteria-hungry viruses called bacteriophages

  • that all work together to prevent biofilms from forming.

  • If microbes do become harmful and you get sick,

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

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

  • In fact, the greenish mucus often associated with infections

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

  • This multi-pronged approach to bacterial management

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

  • Even though mucus protects against the infectious bacteria,

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

  • and many are actually beneficial.

  • That's particularly true when they live in mucus,

  • where they can perform important functions,

  • like synthesizing vitamins, suppressing harmful inflammation,

  • and controlling the growth of more harmful species.

  • So even though you probably associate mucus with being ill,

  • it's really helping you stay healthy.

  • Sure, it might seem gross,

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

  • keep your body clean, fight infection, and domesticate a teeming bacterial population?

  • Nope, just mucus.

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

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B2 US TED-Ed mucus harmful body bacteria bacterial

【TED-Ed】How mucus keeps us healthy - Katharina Ribbeck

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    SylviaQQ posted on 2016/03/03
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