1 00:00:02,040 --> 00:00:07,320 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, 2 00:00:07,360 --> 00:00:10,000 Speaker 1: I'm your host Lauren volk Bomb, and today's episode is 3 00:00:10,039 --> 00:00:14,200 Speaker 1: another classic from our former host, Christian Sager. Saliva lives 4 00:00:14,200 --> 00:00:16,720 Speaker 1: in our mouths at all times, Controlling it as a 5 00:00:16,800 --> 00:00:20,079 Speaker 1: constant battle for us podcasters. But why do we have it? 6 00:00:20,239 --> 00:00:27,800 Speaker 1: And what's it made of? Christian will explain. Hey, I'm 7 00:00:27,880 --> 00:00:30,720 Speaker 1: Christian Saga and welcome to brain Stuff. Most of us 8 00:00:30,760 --> 00:00:33,479 Speaker 1: think of spit as being gross. I mean, it's not 9 00:00:33,560 --> 00:00:36,560 Speaker 1: as nasty as the acidic bile that spews out of 10 00:00:36,560 --> 00:00:40,199 Speaker 1: a xenomorph scaping map, but it's still pretty gross. And 11 00:00:40,280 --> 00:00:44,080 Speaker 1: let's face it, we've all got saliva, so let's just 12 00:00:44,159 --> 00:00:47,480 Speaker 1: get used to it. Okay, how's it work? What's it for? 13 00:00:47,600 --> 00:00:50,919 Speaker 1: And why do we have to swallow it? Saliva is 14 00:00:51,000 --> 00:00:56,160 Speaker 1: actually an incredibly complex fluid that facilitates lots of necessary functions. 15 00:00:56,440 --> 00:01:00,520 Speaker 1: It lubricates our mouths, moistens our food, assists in diggestion, 16 00:01:00,680 --> 00:01:05,480 Speaker 1: protects our teeth, and even defends our mouths from microorganisms. 17 00:01:05,880 --> 00:01:08,520 Speaker 1: Saliva is made by a group of cells called salivary 18 00:01:08,560 --> 00:01:12,600 Speaker 1: glands that deliver it into our mouths through ducts. Humans 19 00:01:12,640 --> 00:01:16,640 Speaker 1: have four kinds of salivary glands. First, there's the parotid glands, 20 00:01:16,680 --> 00:01:20,319 Speaker 1: which are opposite our front lower molars and nearly parallel 21 00:01:20,360 --> 00:01:23,560 Speaker 1: to our ear lobes. These secrete a thin liquid that's 22 00:01:23,600 --> 00:01:28,440 Speaker 1: full of rich antibacterial proteins and compounds that remineralize our teeth. 23 00:01:28,800 --> 00:01:31,560 Speaker 1: They don't care whether you're chewing on bread or a 24 00:01:31,560 --> 00:01:34,560 Speaker 1: piece of plastic, The parotids will set to work on 25 00:01:34,720 --> 00:01:39,679 Speaker 1: anything in your mouth. Next, there's the submandibular glands, which 26 00:01:39,760 --> 00:01:42,760 Speaker 1: are shaped kind of like eggs and are embedded below 27 00:01:42,840 --> 00:01:45,720 Speaker 1: the floor of the mouth, just above the throat. These 28 00:01:45,800 --> 00:01:49,280 Speaker 1: produce a more viscous fluid used to lubricate the throat 29 00:01:49,520 --> 00:01:52,720 Speaker 1: and mouth. Also below the floor of the mouth, there's 30 00:01:52,760 --> 00:01:56,960 Speaker 1: these sublingual glands, which are shaped like almonds. They produce 31 00:01:57,040 --> 00:02:01,480 Speaker 1: similar lubricating secretions. And finally, there's a fourth salivary gland 32 00:02:01,520 --> 00:02:04,520 Speaker 1: that covers the tongue and lining of our mouths with 33 00:02:04,720 --> 00:02:08,000 Speaker 1: hundreds of smaller glands. You know how sometimes you feel 34 00:02:08,080 --> 00:02:11,320 Speaker 1: small bumps on your inner lip. That's them, And while 35 00:02:11,360 --> 00:02:15,800 Speaker 1: they lubricate the mouth, they also protect it against infections. Okay, 36 00:02:15,800 --> 00:02:18,839 Speaker 1: so that's a lot of saliva being secreted by those 37 00:02:18,919 --> 00:02:22,760 Speaker 1: four different glands. It's mostly made of water, and it 38 00:02:22,919 --> 00:02:27,320 Speaker 1: also contains enzymes that break down food for digestion and 39 00:02:27,400 --> 00:02:31,880 Speaker 1: do the whole protection from infection thing. When you pool 40 00:02:31,960 --> 00:02:35,799 Speaker 1: all that saliva together, it's filled with minerals and proteins 41 00:02:35,840 --> 00:02:39,239 Speaker 1: that also maintain our teeth. We can basically break down 42 00:02:39,240 --> 00:02:45,440 Speaker 1: saliva into two categories, stimulated and unstimulated. The stimulated kind 43 00:02:45,600 --> 00:02:48,120 Speaker 1: is what comes from the parotid glands and makes up 44 00:02:48,280 --> 00:02:52,320 Speaker 1: seventy of the two to three pints of saliva we 45 00:02:52,400 --> 00:02:57,359 Speaker 1: generate a day. The main enzyme in stimulated saliva is ammylase, 46 00:02:57,760 --> 00:03:00,840 Speaker 1: used to break down starches into simple sugar our bodies 47 00:03:00,880 --> 00:03:02,960 Speaker 1: make use of. You know how when you chew on 48 00:03:03,040 --> 00:03:07,200 Speaker 1: bread a sweet taste slowly emerges. That's amylase at work. 49 00:03:07,560 --> 00:03:11,519 Speaker 1: Stimulated saliva also balances the amount of acid in our mouths. 50 00:03:11,680 --> 00:03:15,600 Speaker 1: Anything under a pH of four will dissolve calcium phosphate, 51 00:03:15,680 --> 00:03:18,680 Speaker 1: the stuff our tooth enamel is made of. We consume 52 00:03:19,120 --> 00:03:23,680 Speaker 1: lots of things with the lower phs than that, vinegar, soda, citrus, juices, 53 00:03:23,720 --> 00:03:27,200 Speaker 1: and wine. You know how soda dissolves rust, Well, it 54 00:03:27,200 --> 00:03:29,240 Speaker 1: would do the same thing to our teeth if it 55 00:03:29,320 --> 00:03:33,200 Speaker 1: weren't for saliva. There actually isn't a lot known about 56 00:03:33,440 --> 00:03:38,320 Speaker 1: unstimulated saliva because it's difficult to collect, but it's always 57 00:03:38,360 --> 00:03:42,120 Speaker 1: flowing in the background. It's pretty viscous and stringy because 58 00:03:42,120 --> 00:03:45,880 Speaker 1: of a long chain of amino acids called musans. This 59 00:03:46,080 --> 00:03:50,760 Speaker 1: stickiness is what lets unstimulated saliva form a protective film 60 00:03:50,840 --> 00:03:53,920 Speaker 1: on the surface of our teeth. The proteins in there 61 00:03:53,920 --> 00:03:57,760 Speaker 1: both remineralize the enamel of our teeth and trapped bacteria, 62 00:03:57,840 --> 00:04:01,360 Speaker 1: which is swallowed and destroyed in the fiery pits of 63 00:04:01,360 --> 00:04:06,200 Speaker 1: our stomach acids. Speaking of stomachs, saliva is hugely important 64 00:04:06,240 --> 00:04:09,280 Speaker 1: to our digestion. It moistens dry food, and like I 65 00:04:09,320 --> 00:04:12,920 Speaker 1: mentioned earlier, it's saliva that starts breaking down starch so 66 00:04:12,960 --> 00:04:16,560 Speaker 1: we can eat it. It also helps slide that food 67 00:04:16,720 --> 00:04:20,360 Speaker 1: right down your esophagus and into your belly. And most importantly, 68 00:04:20,440 --> 00:04:24,080 Speaker 1: saliva alters the taste of foods, making them more palatable. 69 00:04:24,320 --> 00:04:27,640 Speaker 1: That's right. The bacteria in saliva is what brings out 70 00:04:27,680 --> 00:04:31,760 Speaker 1: the rich flavor and wine onions, peppers, and more, and 71 00:04:31,960 --> 00:04:36,599 Speaker 1: it even turns odorless compounds in fruit and vegetables into 72 00:04:36,720 --> 00:04:42,720 Speaker 1: much more aromatic chemicals called fields. Some researchers even speculate 73 00:04:42,800 --> 00:04:45,880 Speaker 1: that we could use the compounds in spit to flavor 74 00:04:45,920 --> 00:04:49,799 Speaker 1: food in our kitchen when it's not digesting and making 75 00:04:49,839 --> 00:04:54,120 Speaker 1: things taste great. Saliva is also a lethal killer of germs. 76 00:04:54,560 --> 00:04:57,039 Speaker 1: The wonder of saliva is that it's both full of 77 00:04:57,080 --> 00:05:02,360 Speaker 1: bacteria and an antimicrobial sassin. In fact, spit is so 78 00:05:02,400 --> 00:05:06,160 Speaker 1: good at cleaning some art conservators use it on fragile 79 00:05:06,240 --> 00:05:10,839 Speaker 1: surfaces instead of chemical solutions. This is because saliva has 80 00:05:10,920 --> 00:05:15,039 Speaker 1: anti clumping properties that keep bacteria from forming colonies on 81 00:05:15,080 --> 00:05:19,440 Speaker 1: our teeth and gums. Proteins called his statins not only 82 00:05:19,560 --> 00:05:23,120 Speaker 1: hunt down bacteria and kill them, but also have been 83 00:05:23,160 --> 00:05:26,520 Speaker 1: shown to speed up the healing process of wounds inside 84 00:05:26,560 --> 00:05:30,840 Speaker 1: the mouth. Seriously, this is some wolverine style regeneration. Here, 85 00:05:31,160 --> 00:05:34,559 Speaker 1: wounds that take several weeks to heal in our skin 86 00:05:35,160 --> 00:05:38,680 Speaker 1: disappear within a week in our mouth. In some cultures, 87 00:05:38,720 --> 00:05:42,279 Speaker 1: a mother will even spit in her infant's mouth to 88 00:05:42,440 --> 00:05:47,320 Speaker 1: teach their immune system how to produce antibodies and destroy pathogens. 89 00:05:47,360 --> 00:05:51,320 Speaker 1: Because of all the antibodies already in the mother's saliva, 90 00:05:51,760 --> 00:05:56,799 Speaker 1: this introduces the infant to bacteria without getting them sick. Finally, 91 00:05:57,040 --> 00:06:00,680 Speaker 1: did you know that our saliva contains our entire genetic blueprint. 92 00:06:00,920 --> 00:06:02,960 Speaker 1: If you're trying to get away from a crime scene, 93 00:06:03,400 --> 00:06:06,280 Speaker 1: don't spit on anything because so many cells from the 94 00:06:06,320 --> 00:06:10,320 Speaker 1: inside of your cheeks slough off into saliva. It only 95 00:06:10,360 --> 00:06:14,159 Speaker 1: takes half an eye dropper worth of spit to sample 96 00:06:14,240 --> 00:06:17,440 Speaker 1: your d NA. You can even take a sample yourself, 97 00:06:17,720 --> 00:06:20,839 Speaker 1: send it in the mail, and get your own genetic information. 98 00:06:21,080 --> 00:06:25,120 Speaker 1: This includes health data like your susceptibility to certain diseases. 99 00:06:25,520 --> 00:06:30,000 Speaker 1: So in the future, scientists hope to catalog every single 100 00:06:30,080 --> 00:06:34,599 Speaker 1: salivary protein. It's possible that saliva could even replace blood 101 00:06:34,600 --> 00:06:39,239 Speaker 1: for testing things like alcohol, illegal drugs, and HIV antibodies. 102 00:06:39,720 --> 00:06:44,000 Speaker 1: Some even theorized that your body could dispense medications automatically 103 00:06:44,320 --> 00:06:53,760 Speaker 1: by modifying the salivary glands genetically. Today's episode was written 104 00:06:53,760 --> 00:06:56,640 Speaker 1: by somebody on the House to Work staff, perhaps Martial 105 00:06:56,680 --> 00:06:59,480 Speaker 1: Brain himself, our original host. The records have been lost 106 00:06:59,480 --> 00:07:02,320 Speaker 1: to time, but it was produced by Tyler Clang. But 107 00:07:02,440 --> 00:07:04,880 Speaker 1: for more on this and lots of other timeless topics, 108 00:07:04,960 --> 00:07:18,600 Speaker 1: visit our home planet, How Stuff Works dot Com.