WEBVTT - BrainStuff Classics: How Does Saliva Work? 0:00:02.040 --> 0:00:07.320 Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, 0:00:07.360 --> 0:00:10.000 I'm your host Lauren volk Bomb, and today's episode is 0:00:10.039 --> 0:00:14.200 another classic from our former host, Christian Sager. Saliva lives 0:00:14.200 --> 0:00:16.720 in our mouths at all times, Controlling it as a 0:00:16.800 --> 0:00:20.079 constant battle for us podcasters. But why do we have it? 0:00:20.239 --> 0:00:27.800 And what's it made of? Christian will explain. Hey, I'm 0:00:27.880 --> 0:00:30.720 Christian Saga and welcome to brain Stuff. Most of us 0:00:30.760 --> 0:00:33.479 think of spit as being gross. I mean, it's not 0:00:33.560 --> 0:00:36.560 as nasty as the acidic bile that spews out of 0:00:36.560 --> 0:00:40.199 a xenomorph scaping map, but it's still pretty gross. And 0:00:40.280 --> 0:00:44.080 let's face it, we've all got saliva, so let's just 0:00:44.159 --> 0:00:47.480 get used to it. Okay, how's it work? What's it for? 0:00:47.600 --> 0:00:50.919 And why do we have to swallow it? Saliva is 0:00:51.000 --> 0:00:56.160 actually an incredibly complex fluid that facilitates lots of necessary functions. 0:00:56.440 --> 0:01:00.520 It lubricates our mouths, moistens our food, assists in diggestion, 0:01:00.680 --> 0:01:05.480 protects our teeth, and even defends our mouths from microorganisms. 0:01:05.880 --> 0:01:08.520 Saliva is made by a group of cells called salivary 0:01:08.560 --> 0:01:12.600 glands that deliver it into our mouths through ducts. Humans 0:01:12.640 --> 0:01:16.640 have four kinds of salivary glands. First, there's the parotid glands, 0:01:16.680 --> 0:01:20.319 which are opposite our front lower molars and nearly parallel 0:01:20.360 --> 0:01:23.560 to our ear lobes. These secrete a thin liquid that's 0:01:23.600 --> 0:01:28.440 full of rich antibacterial proteins and compounds that remineralize our teeth. 0:01:28.800 --> 0:01:31.560 They don't care whether you're chewing on bread or a 0:01:31.560 --> 0:01:34.560 piece of plastic, The parotids will set to work on 0:01:34.720 --> 0:01:39.679 anything in your mouth. Next, there's the submandibular glands, which 0:01:39.760 --> 0:01:42.760 are shaped kind of like eggs and are embedded below 0:01:42.840 --> 0:01:45.720 the floor of the mouth, just above the throat. These 0:01:45.800 --> 0:01:49.280 produce a more viscous fluid used to lubricate the throat 0:01:49.520 --> 0:01:52.720 and mouth. Also below the floor of the mouth, there's 0:01:52.760 --> 0:01:56.960 these sublingual glands, which are shaped like almonds. They produce 0:01:57.040 --> 0:02:01.480 similar lubricating secretions. And finally, there's a fourth salivary gland 0:02:01.520 --> 0:02:04.520 that covers the tongue and lining of our mouths with 0:02:04.720 --> 0:02:08.000 hundreds of smaller glands. You know how sometimes you feel 0:02:08.080 --> 0:02:11.320 small bumps on your inner lip. That's them, And while 0:02:11.360 --> 0:02:15.800 they lubricate the mouth, they also protect it against infections. Okay, 0:02:15.800 --> 0:02:18.839 so that's a lot of saliva being secreted by those 0:02:18.919 --> 0:02:22.760 four different glands. It's mostly made of water, and it 0:02:22.919 --> 0:02:27.320 also contains enzymes that break down food for digestion and 0:02:27.400 --> 0:02:31.880 do the whole protection from infection thing. When you pool 0:02:31.960 --> 0:02:35.799 all that saliva together, it's filled with minerals and proteins 0:02:35.840 --> 0:02:39.239 that also maintain our teeth. We can basically break down 0:02:39.240 --> 0:02:45.440 saliva into two categories, stimulated and unstimulated. The stimulated kind 0:02:45.600 --> 0:02:48.120 is what comes from the parotid glands and makes up 0:02:48.280 --> 0:02:52.320 seventy of the two to three pints of saliva we 0:02:52.400 --> 0:02:57.359 generate a day. The main enzyme in stimulated saliva is ammylase, 0:02:57.760 --> 0:03:00.840 used to break down starches into simple sugar our bodies 0:03:00.880 --> 0:03:02.960 make use of. You know how when you chew on 0:03:03.040 --> 0:03:07.200 bread a sweet taste slowly emerges. That's amylase at work. 0:03:07.560 --> 0:03:11.519 Stimulated saliva also balances the amount of acid in our mouths. 0:03:11.680 --> 0:03:15.600 Anything under a pH of four will dissolve calcium phosphate, 0:03:15.680 --> 0:03:18.680 the stuff our tooth enamel is made of. We consume 0:03:19.120 --> 0:03:23.680 lots of things with the lower phs than that, vinegar, soda, citrus, juices, 0:03:23.720 --> 0:03:27.200 and wine. You know how soda dissolves rust, Well, it 0:03:27.200 --> 0:03:29.240 would do the same thing to our teeth if it 0:03:29.320 --> 0:03:33.200 weren't for saliva. There actually isn't a lot known about 0:03:33.440 --> 0:03:38.320 unstimulated saliva because it's difficult to collect, but it's always 0:03:38.360 --> 0:03:42.120 flowing in the background. It's pretty viscous and stringy because 0:03:42.120 --> 0:03:45.880 of a long chain of amino acids called musans. This 0:03:46.080 --> 0:03:50.760 stickiness is what lets unstimulated saliva form a protective film 0:03:50.840 --> 0:03:53.920 on the surface of our teeth. The proteins in there 0:03:53.920 --> 0:03:57.760 both remineralize the enamel of our teeth and trapped bacteria, 0:03:57.840 --> 0:04:01.360 which is swallowed and destroyed in the fiery pits of 0:04:01.360 --> 0:04:06.200 our stomach acids. Speaking of stomachs, saliva is hugely important 0:04:06.240 --> 0:04:09.280 to our digestion. It moistens dry food, and like I 0:04:09.320 --> 0:04:12.920 mentioned earlier, it's saliva that starts breaking down starch so 0:04:12.960 --> 0:04:16.560 we can eat it. It also helps slide that food 0:04:16.720 --> 0:04:20.360 right down your esophagus and into your belly. And most importantly, 0:04:20.440 --> 0:04:24.080 saliva alters the taste of foods, making them more palatable. 0:04:24.320 --> 0:04:27.640 That's right. The bacteria in saliva is what brings out 0:04:27.680 --> 0:04:31.760 the rich flavor and wine onions, peppers, and more, and 0:04:31.960 --> 0:04:36.599 it even turns odorless compounds in fruit and vegetables into 0:04:36.720 --> 0:04:42.720 much more aromatic chemicals called fields. Some researchers even speculate 0:04:42.800 --> 0:04:45.880 that we could use the compounds in spit to flavor 0:04:45.920 --> 0:04:49.799 food in our kitchen when it's not digesting and making 0:04:49.839 --> 0:04:54.120 things taste great. Saliva is also a lethal killer of germs. 0:04:54.560 --> 0:04:57.039 The wonder of saliva is that it's both full of 0:04:57.080 --> 0:05:02.360 bacteria and an antimicrobial sassin. In fact, spit is so 0:05:02.400 --> 0:05:06.160 good at cleaning some art conservators use it on fragile 0:05:06.240 --> 0:05:10.839 surfaces instead of chemical solutions. This is because saliva has 0:05:10.920 --> 0:05:15.039 anti clumping properties that keep bacteria from forming colonies on 0:05:15.080 --> 0:05:19.440 our teeth and gums. Proteins called his statins not only 0:05:19.560 --> 0:05:23.120 hunt down bacteria and kill them, but also have been 0:05:23.160 --> 0:05:26.520 shown to speed up the healing process of wounds inside 0:05:26.560 --> 0:05:30.840 the mouth. Seriously, this is some wolverine style regeneration. Here, 0:05:31.160 --> 0:05:34.559 wounds that take several weeks to heal in our skin 0:05:35.160 --> 0:05:38.680 disappear within a week in our mouth. In some cultures, 0:05:38.720 --> 0:05:42.279 a mother will even spit in her infant's mouth to 0:05:42.440 --> 0:05:47.320 teach their immune system how to produce antibodies and destroy pathogens. 0:05:47.360 --> 0:05:51.320 Because of all the antibodies already in the mother's saliva, 0:05:51.760 --> 0:05:56.799 this introduces the infant to bacteria without getting them sick. Finally, 0:05:57.040 --> 0:06:00.680 did you know that our saliva contains our entire genetic blueprint. 0:06:00.920 --> 0:06:02.960 If you're trying to get away from a crime scene, 0:06:03.400 --> 0:06:06.280 don't spit on anything because so many cells from the 0:06:06.320 --> 0:06:10.320 inside of your cheeks slough off into saliva. It only 0:06:10.360 --> 0:06:14.159 takes half an eye dropper worth of spit to sample 0:06:14.240 --> 0:06:17.440 your d NA. You can even take a sample yourself, 0:06:17.720 --> 0:06:20.839 send it in the mail, and get your own genetic information. 0:06:21.080 --> 0:06:25.120 This includes health data like your susceptibility to certain diseases. 0:06:25.520 --> 0:06:30.000 So in the future, scientists hope to catalog every single 0:06:30.080 --> 0:06:34.599 salivary protein. It's possible that saliva could even replace blood 0:06:34.600 --> 0:06:39.239 for testing things like alcohol, illegal drugs, and HIV antibodies. 0:06:39.720 --> 0:06:44.000 Some even theorized that your body could dispense medications automatically 0:06:44.320 --> 0:06:53.760 by modifying the salivary glands genetically. Today's episode was written 0:06:53.760 --> 0:06:56.640 by somebody on the House to Work staff, perhaps Martial 0:06:56.680 --> 0:06:59.480 Brain himself, our original host. The records have been lost 0:06:59.480 --> 0:07:02.320 to time, but it was produced by Tyler Clang. But 0:07:02.440 --> 0:07:04.880 for more on this and lots of other timeless topics, 0:07:04.960 --> 0:07:18.600 visit our home planet, How Stuff Works dot Com.