WEBVTT - How Does Saliva Work?

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<v Speaker 1>I'm Matt, I'm Null, I'm Ben, and we are stuff

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<v Speaker 1>you get your podcasts. Welcome to brain Stuff from How

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<v Speaker 1>Stuff Works. Hey, I'm Christian Seger and welcome to brain Stuff.

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<v Speaker 1>Most of us think of spit as being gross. I mean,

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<v Speaker 1>it's not as nasty as the acidic bile that spews

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<v Speaker 1>out of a xenomorph escaping map, but it's still pretty gross.

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<v Speaker 1>And let's face it, we've all got saliva, so let's

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<v Speaker 1>just get used to it. Okay, how's it work, what's

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<v Speaker 1>it for? And why do we have to swallow it?

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<v Speaker 1>Saliva is actually an incredibly complex fluid that facilitates lots

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<v Speaker 1>of necessary functions. It lubricates our mouth, moistens our food,

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<v Speaker 1>assists in digestion, protects our teeth, and even defends our

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<v Speaker 1>mouths from microorganisms. Saliva is made by a group of

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<v Speaker 1>cells called salivary glands that deliver it into our mouths

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<v Speaker 1>through ducts. Humans have four kinds of salivary glands. First,

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<v Speaker 1>there's the parotid glands, which are opposite our front lower

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<v Speaker 1>molars and nearly parallel to our ear lobes. These secrete

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<v Speaker 1>a thin liquid that's full of rich antibacterial proteins and

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<v Speaker 1>compounds that remineralize our teeth. They don't care whether you're

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<v Speaker 1>chewing on bread or a piece of plastic, The parotids

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<v Speaker 1>will set to work on anything in your mouth. Next,

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<v Speaker 1>there's the submandibular glands, which are shaped kind of like

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<v Speaker 1>eggs and are embedded below the floor of the mouth,

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<v Speaker 1>just above the throat. These produce a more viscous fluid

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<v Speaker 1>used to lubricate the throat and mouth. Also below the

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<v Speaker 1>floor of the mouth, there's these sublingual glands, which are

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<v Speaker 1>shaped like almonds. They produce similar loop bricating secretions. And finally,

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<v Speaker 1>there's a fourth salivary gland that covers the tongue and

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<v Speaker 1>lining of our mouths with hundreds of smaller glands. You

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<v Speaker 1>know how sometimes you feel small bumps on your inner lip.

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<v Speaker 1>That's them, and while they lubricate the mouth, they also

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<v Speaker 1>protect it against infections. Okay, so that's a lot of

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<v Speaker 1>saliva being secreted by those four different glands. It's mostly

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<v Speaker 1>made of water, and it also contains enzymes that break

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<v Speaker 1>down food for digestion and do the whole protection from

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<v Speaker 1>infection thing. When you pool all that saliva together, it's

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<v Speaker 1>filled with minerals and proteins that also maintain our teeth.

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<v Speaker 1>We can basically break down saliva into two categories, stimulated

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<v Speaker 1>and unstimulated. The stimulated kind is what comes from the

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<v Speaker 1>parotid glands and makes up seventy of the two to

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<v Speaker 1>three pints of saliva we generate a day. The main

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<v Speaker 1>enzyme in stimulated saliva is ammylase, used to break down

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<v Speaker 1>starches into simple sugars our bodies make use of. You

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<v Speaker 1>know how when you chew on bread a sweet taste

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<v Speaker 1>slowly emerges. That's amylase at work. Stimulated saliva also balances

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<v Speaker 1>the amount of acid in our mouths. Anything under a

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<v Speaker 1>pH of four will dissolve calcium phosphate, the stuff our

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<v Speaker 1>tooth enamel is made of. We consume lots of things

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<v Speaker 1>with a lower pH than that, vinegar, soda, citrus, juices,

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<v Speaker 1>and wine. You know how soda dissolves rust, Well, it

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<v Speaker 1>would do the same thing to our teeth if it

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<v Speaker 1>weren't for saliva. There actually isn't a lot known about

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<v Speaker 1>unstimulated saliva because it's difficult to collect, but it's always

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<v Speaker 1>flowing in the background. It's pretty viscous and stringy because

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<v Speaker 1>of a long chain of amino acids called musans. This

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<v Speaker 1>stickiness is what lets unstimulated saliva form a protective film

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<v Speaker 1>on the surface of our teeth. The proteins in there

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<v Speaker 1>both remineralize the enamel of our teeth and trapped back

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<v Speaker 1>to your which is swallowed and destroyed in the fiery

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<v Speaker 1>pits of our stomach acids. Speaking of stomachs, saliva is

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<v Speaker 1>hugely important to our digestion. It moistens dry food, and

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<v Speaker 1>like I mentioned earlier, it's saliva that starts breaking down

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<v Speaker 1>starch so we can eat it. It also helps slide

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<v Speaker 1>that food right down your esophagus and into your belly.

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<v Speaker 1>And most importantly, saliva alters the taste of foods, making

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<v Speaker 1>them more palatable. That's right. The bacteria in saliva is

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<v Speaker 1>what brings out the rich flavor and wine onions, peppers,

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<v Speaker 1>and more, and it even turns odorless compounds in fruit

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<v Speaker 1>and vegetables into much more aromatic chemicals called fields. Some

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<v Speaker 1>researchers even speculate that we could use the compounds in

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<v Speaker 1>spit to flavor food in our kitchen when it's not

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<v Speaker 1>digesting and making things taste great. Saliva is also a

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<v Speaker 1>lethal killer of germs. The wonder of saliva is that

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<v Speaker 1>it's both full of bacteria and an anti microbial assassin.

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<v Speaker 1>In fact, spit is so good at cleaning some art

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<v Speaker 1>conservators use it on fragile surfaces instead of chemical solutions.

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<v Speaker 1>This is because saliva has anti clumping properties that keep

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<v Speaker 1>bacteria from forming colonies on our teeth and gums. Proteins

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<v Speaker 1>called his statins not only hunt down bacteria and kill them,

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<v Speaker 1>but also have been shown to speed up the healing

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<v Speaker 1>process of wounds inside the mouth. Seriously, this is some

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<v Speaker 1>wolverine style regeneration. Here, wounds that take several weeks to

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<v Speaker 1>heal in our skin disappear within a week in our mouth.

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<v Speaker 1>In some cultures, a mother will even spit in her

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<v Speaker 1>infant's mouth to teach their immune system how to produce

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<v Speaker 1>antibodies and destroy pathogens. Because of all the antibodies already

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<v Speaker 1>in the mother saliva, this introduces the infant to bacteria

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<v Speaker 1>without getting them sick. Finally, did you know that our

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<v Speaker 1>saliva contains our entire genetic blueprint. If you're trying to

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<v Speaker 1>get away from a crime scene, don't spit on anything

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<v Speaker 1>because so many cells from the inside of your cheeks

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<v Speaker 1>slough off into saliva. It only takes half an eye

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<v Speaker 1>dropper worth of spit to sample your DNA. You can

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<v Speaker 1>even take a sample yourself, send it in the mail,

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<v Speaker 1>and get your own genetic information. This includes health data

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<v Speaker 1>like your susceptibility to certain diseases, so in the future,

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<v Speaker 1>scientists hope to catalog every single salivary protein. It's possible

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<v Speaker 1>that saliva could even replace blood for testing things like alcohol,

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<v Speaker 1>illegal drugs, and HIV antibodies. Some even theorize that your

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<v Speaker 1>body could dispense medications automatically by modifying the salivary glands genetically.

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<v Speaker 1>Check out the brain stuff channel on YouTube, and for

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<v Speaker 1>more on this and thousands of other topics, visit how

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<v Speaker 1>stuff works dot com.