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Speaker 1: Stuff Works. Hey, I'm Christian Seger and welcome to brain Stuff.
Speaker 1: Most of us think of spit as being gross. I mean,
Speaker 1: it's not as nasty as the acidic bile that spews
Speaker 1: out of a xenomorph escaping map, but it's still pretty gross.
Speaker 1: And let's face it, we've all got saliva, so let's
Speaker 1: just get used to it. Okay, how's it work, what's
Speaker 1: it for? And why do we have to swallow it?
Speaker 1: Saliva is actually an incredibly complex fluid that facilitates lots
Speaker 1: of necessary functions. It lubricates our mouth, moistens our food,
Speaker 1: assists in digestion, protects our teeth, and even defends our
Speaker 1: mouths from microorganisms. Saliva is made by a group of
Speaker 1: cells called salivary glands that deliver it into our mouths
Speaker 1: through ducts. Humans have four kinds of salivary glands. First,
Speaker 1: there's the parotid glands, which are opposite our front lower
Speaker 1: molars and nearly parallel to our ear lobes. These secrete
Speaker 1: a thin liquid that's full of rich antibacterial proteins and
Speaker 1: compounds that remineralize our teeth. They don't care whether you're
Speaker 1: chewing on bread or a piece of plastic, The parotids
Speaker 1: will set to work on anything in your mouth. Next,
Speaker 1: there's the submandibular glands, which are shaped kind of like
Speaker 1: eggs and are embedded below the floor of the mouth,
Speaker 1: just above the throat. These produce a more viscous fluid
Speaker 1: used to lubricate the throat and mouth. Also below the
Speaker 1: floor of the mouth, there's these sublingual glands, which are
Speaker 1: shaped like almonds. They produce similar loop bricating secretions. And finally,
Speaker 1: there's a fourth salivary gland that covers the tongue and
Speaker 1: lining of our mouths with hundreds of smaller glands. You
Speaker 1: know how sometimes you feel small bumps on your inner lip.
Speaker 1: That's them, and while they lubricate the mouth, they also
Speaker 1: protect it against infections. Okay, so that's a lot of
Speaker 1: saliva being secreted by those four different glands. It's mostly
Speaker 1: made of water, and it also contains enzymes that break
Speaker 1: down food for digestion and do the whole protection from
Speaker 1: infection thing. When you pool all that saliva together, it's
Speaker 1: filled with minerals and proteins that also maintain our teeth.
Speaker 1: We can basically break down saliva into two categories, stimulated
Speaker 1: and unstimulated. The stimulated kind is what comes from the
Speaker 1: parotid glands and makes up seventy of the two to
Speaker 1: three pints of saliva we generate a day. The main
Speaker 1: enzyme in stimulated saliva is ammylase, used to break down
Speaker 1: starches into simple sugars our bodies make use of. You
Speaker 1: know how when you chew on bread a sweet taste
Speaker 1: slowly emerges. That's amylase at work. Stimulated saliva also balances
Speaker 1: the amount of acid in our mouths. Anything under a
Speaker 1: pH of four will dissolve calcium phosphate, the stuff our
Speaker 1: tooth enamel is made of. We consume lots of things
Speaker 1: with a lower pH than that, vinegar, soda, citrus, juices,
Speaker 1: and wine. You know how soda dissolves rust, Well, it
Speaker 1: would do the same thing to our teeth if it
Speaker 1: weren't for saliva. There actually isn't a lot known about
Speaker 1: unstimulated saliva because it's difficult to collect, but it's always
Speaker 1: flowing in the background. It's pretty viscous and stringy because
Speaker 1: of a long chain of amino acids called musans. This
Speaker 1: stickiness is what lets unstimulated saliva form a protective film
Speaker 1: on the surface of our teeth. The proteins in there
Speaker 1: both remineralize the enamel of our teeth and trapped back
Speaker 1: to your which is swallowed and destroyed in the fiery
Speaker 1: pits of our stomach acids. Speaking of stomachs, saliva is
Speaker 1: hugely important to our digestion. It moistens dry food, and
Speaker 1: like I mentioned earlier, it's saliva that starts breaking down
Speaker 1: starch so we can eat it. It also helps slide
Speaker 1: that food right down your esophagus and into your belly.
Speaker 1: And most importantly, saliva alters the taste of foods, making
Speaker 1: them more palatable. That's right. The bacteria in saliva is
Speaker 1: what brings out the rich flavor and wine onions, peppers,
Speaker 1: and more, and it even turns odorless compounds in fruit
Speaker 1: and vegetables into much more aromatic chemicals called fields. Some
Speaker 1: researchers even speculate that we could use the compounds in
Speaker 1: spit to flavor food in our kitchen when it's not
Speaker 1: digesting and making things taste great. Saliva is also a
Speaker 1: lethal killer of germs. The wonder of saliva is that
Speaker 1: it's both full of bacteria and an anti microbial assassin.
Speaker 1: In fact, spit is so good at cleaning some art
Speaker 1: conservators use it on fragile surfaces instead of chemical solutions.
Speaker 1: This is because saliva has anti clumping properties that keep
Speaker 1: bacteria from forming colonies on our teeth and gums. Proteins
Speaker 1: called his statins not only hunt down bacteria and kill them,
Speaker 1: but also have been shown to speed up the healing
Speaker 1: process of wounds inside the mouth. Seriously, this is some
Speaker 1: wolverine style regeneration. Here, wounds that take several weeks to
Speaker 1: heal in our skin disappear within a week in our mouth.
Speaker 1: In some cultures, a mother will even spit in her
Speaker 1: infant's mouth to teach their immune system how to produce
Speaker 1: antibodies and destroy pathogens. Because of all the antibodies already
Speaker 1: in the mother saliva, this introduces the infant to bacteria
Speaker 1: without getting them sick. Finally, did you know that our
Speaker 1: saliva contains our entire genetic blueprint. If you're trying to
Speaker 1: get away from a crime scene, don't spit on anything
Speaker 1: because so many cells from the inside of your cheeks
Speaker 1: slough off into saliva. It only takes half an eye
Speaker 1: dropper worth of spit to sample your DNA. You can
Speaker 1: even take a sample yourself, send it in the mail,
Speaker 1: and get your own genetic information. This includes health data
Speaker 1: like your susceptibility to certain diseases, so in the future,
Speaker 1: scientists hope to catalog every single salivary protein. It's possible
Speaker 1: that saliva could even replace blood for testing things like alcohol,
Speaker 1: illegal drugs, and HIV antibodies. Some even theorize that your
Speaker 1: body could dispense medications automatically by modifying the salivary glands genetically.
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Speaker 1: more on this and thousands of other topics, visit how
Speaker 1: stuff works dot com.