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