[PBSDS BUMPER] We all know how the journey through the digestive
system ends, but few give much thought to how it begins. If the mouth is the doorway,
saliva is the greeter, one of the most important substances produced by the body, yet one of
the most overlooked, and to many, one of the grossest… conjuring up words like “bleep” Wait, what did I say? “Bleep”?
“M-O-I-S-T”… I can’t say “Bleep”? Ok, fine then. Let’s move on(moist). [IOTBS INTRO] Perhaps the best way to really appreciate saliva, is to learn what it’d be like to
live without it. I give you the time-honored scientific tradition of, the saltine challenge (PARTY NOISES) Six crackers, no water, one minute on the clock. (MUSIC) I can’t swallow There’s nothing in my mouth To make saliva, cells pump out salts, and
because of osmosis, that draws out water. Unlike with tears or sweat, the salt is then
taken back up by the glands, leaving you with something that’s about 99% water. The other
1% is proteins and other molecules which give saliva that sticky feel you know and… well,
have feelings about, but that 1% is also where most of the cool spit happens. But not all saliva is secreted equal, we pump
out two different brands of mouth juice. Unstimulated saliva is secreted by hundreds
of tiny glands all over our mouth, and we make it essentially all the time. This saliva
contains a special ingredient called mucin, which is a protein that loves to soak up water,
creating a kind of gel which forms a thin, protective coating all over your mouth parts.
Mucin is basically why saliva sounds like this [GROSS WET MOUTH NOISES] On the other gland, stimulated saliva is…
what it sounds like, it flows when we smell something delicious or… chew. Really doesn’t
matter WHAT you chew, could be anything, but I suggest food… or maybe gum. We have special
sensors beneath our teeth, when they feel the pressure of mastication, they send a signal
to crank up the spit factories. Super sour or salty foods also stimulate saliva,
basically to dilute the acids or salts and protect your mouth. You can test this, just
put a drop of lemon juice on your tongue and wait for the floodgates to open. Lots of people think sugar causes tooth decay,
but it’s really caused by acids released by bacteria who EAT the sugar. Saliva dilutes
that nasty stuff, so you can keep your teeth. Since we make less saliva when we’re asleep,
that’s prime-time for tooth decay… but you always brush before bed, right? You probably know there’s two salivary glands
under your tongue, but most saliva that comes from chomping and tasting is made by the parotid
gland, situated between your ear and mouth. It’s not here, or here so much… but right
here. Obviously, this type of saliva makes eating
possible by lubricating your food… but it also contains a bunch of proteins.
The exact saliva protein mix varies throughout the day, but the most abundant is amylase.
Amylase is an enzyme, it chops long, complex sugars like starch into simple ones, because
glucose is what cells crave. Try this: Hold a bite of cracker in your mouth
without swallowing and let your saliva go to work. After a few minutes, a sweet taste
begins to take over as the starch in the cracker is broken down into sugar. Sweet Proteins are one of the reasons babies drool
so much. Baby saliva contains enzymes that help digest milk, so when milk’s your only
food, you make a lot of drool. In fact, enzymes from saliva that break down
starch, protein, and fat are manufactured on large scales and added to laundry and dishwashing
detergents to help them literally digest stains. In most cultures, spitting ON someone is just about the grossest, worst thing
you can do, yet we don’t mind swapping spit with the people we love. At least that was
true before you watched this video. I don’t expect that we’ll all stop being
a little weirded out by saliva anytime soon, but if you take a second to chew on the idea,
when it comes to multipurpose liquids, saliva even puts sriracha to shame. Ya know what? Drool rules. Stay curious.