1 00:00:00,440 --> 00:00:03,440 Speaker 1: I'm Matt, I'm Null, I'm Ben, and we are stuff 2 00:00:03,520 --> 00:00:06,080 Speaker 1: they don't want you to know. Each week we cover 3 00:00:06,160 --> 00:00:09,719 Speaker 1: the latest and strangest in fringe science, government cover ups, 4 00:00:09,800 --> 00:00:13,360 Speaker 1: allegations of the paranormal, and more. New episodes come out 5 00:00:13,440 --> 00:00:16,880 Speaker 1: every Friday on iTunes, Spotify, Google Play, in anywhere else 6 00:00:16,960 --> 00:00:24,160 Speaker 1: you get your podcasts. Welcome to brain Stuff from How 7 00:00:24,200 --> 00:00:32,280 Speaker 1: Stuff Works. Hey, I'm Christian Seger and welcome to brain Stuff. 8 00:00:32,479 --> 00:00:35,440 Speaker 1: Most of us think of spit as being gross. I mean, 9 00:00:35,520 --> 00:00:38,559 Speaker 1: it's not as nasty as the acidic bile that spews 10 00:00:38,640 --> 00:00:42,400 Speaker 1: out of a xenomorph escaping map, but it's still pretty gross. 11 00:00:42,440 --> 00:00:46,240 Speaker 1: And let's face it, we've all got saliva, so let's 12 00:00:46,280 --> 00:00:49,360 Speaker 1: just get used to it. Okay, how's it work, what's 13 00:00:49,400 --> 00:00:52,080 Speaker 1: it for? And why do we have to swallow it? 14 00:00:52,400 --> 00:00:57,080 Speaker 1: Saliva is actually an incredibly complex fluid that facilitates lots 15 00:00:57,160 --> 00:01:01,320 Speaker 1: of necessary functions. It lubricates our mouth, moistens our food, 16 00:01:01,600 --> 00:01:05,880 Speaker 1: assists in digestion, protects our teeth, and even defends our 17 00:01:05,920 --> 00:01:09,680 Speaker 1: mouths from microorganisms. Saliva is made by a group of 18 00:01:09,680 --> 00:01:13,160 Speaker 1: cells called salivary glands that deliver it into our mouths 19 00:01:13,160 --> 00:01:17,479 Speaker 1: through ducts. Humans have four kinds of salivary glands. First, 20 00:01:17,680 --> 00:01:20,600 Speaker 1: there's the parotid glands, which are opposite our front lower 21 00:01:20,640 --> 00:01:24,720 Speaker 1: molars and nearly parallel to our ear lobes. These secrete 22 00:01:24,760 --> 00:01:28,480 Speaker 1: a thin liquid that's full of rich antibacterial proteins and 23 00:01:28,560 --> 00:01:32,319 Speaker 1: compounds that remineralize our teeth. They don't care whether you're 24 00:01:32,360 --> 00:01:35,559 Speaker 1: chewing on bread or a piece of plastic, The parotids 25 00:01:35,800 --> 00:01:39,240 Speaker 1: will set to work on anything in your mouth. Next, 26 00:01:39,319 --> 00:01:43,200 Speaker 1: there's the submandibular glands, which are shaped kind of like 27 00:01:43,280 --> 00:01:46,240 Speaker 1: eggs and are embedded below the floor of the mouth, 28 00:01:46,360 --> 00:01:49,840 Speaker 1: just above the throat. These produce a more viscous fluid 29 00:01:50,040 --> 00:01:53,800 Speaker 1: used to lubricate the throat and mouth. Also below the 30 00:01:53,800 --> 00:01:57,240 Speaker 1: floor of the mouth, there's these sublingual glands, which are 31 00:01:57,280 --> 00:02:01,720 Speaker 1: shaped like almonds. They produce similar loop bricating secretions. And finally, 32 00:02:02,040 --> 00:02:05,200 Speaker 1: there's a fourth salivary gland that covers the tongue and 33 00:02:05,360 --> 00:02:08,960 Speaker 1: lining of our mouths with hundreds of smaller glands. You 34 00:02:09,000 --> 00:02:12,040 Speaker 1: know how sometimes you feel small bumps on your inner lip. 35 00:02:12,400 --> 00:02:15,560 Speaker 1: That's them, and while they lubricate the mouth, they also 36 00:02:15,639 --> 00:02:19,320 Speaker 1: protect it against infections. Okay, so that's a lot of 37 00:02:19,360 --> 00:02:23,600 Speaker 1: saliva being secreted by those four different glands. It's mostly 38 00:02:23,639 --> 00:02:27,400 Speaker 1: made of water, and it also contains enzymes that break 39 00:02:27,400 --> 00:02:31,639 Speaker 1: down food for digestion and do the whole protection from 40 00:02:31,800 --> 00:02:36,200 Speaker 1: infection thing. When you pool all that saliva together, it's 41 00:02:36,240 --> 00:02:39,880 Speaker 1: filled with minerals and proteins that also maintain our teeth. 42 00:02:40,240 --> 00:02:44,920 Speaker 1: We can basically break down saliva into two categories, stimulated 43 00:02:44,960 --> 00:02:48,880 Speaker 1: and unstimulated. The stimulated kind is what comes from the 44 00:02:48,880 --> 00:02:52,640 Speaker 1: parotid glands and makes up seventy of the two to 45 00:02:52,800 --> 00:02:56,600 Speaker 1: three pints of saliva we generate a day. The main 46 00:02:56,800 --> 00:03:01,000 Speaker 1: enzyme in stimulated saliva is ammylase, used to break down 47 00:03:01,040 --> 00:03:04,280 Speaker 1: starches into simple sugars our bodies make use of. You 48 00:03:04,280 --> 00:03:06,880 Speaker 1: know how when you chew on bread a sweet taste 49 00:03:06,960 --> 00:03:12,000 Speaker 1: slowly emerges. That's amylase at work. Stimulated saliva also balances 50 00:03:12,000 --> 00:03:14,800 Speaker 1: the amount of acid in our mouths. Anything under a 51 00:03:14,840 --> 00:03:18,799 Speaker 1: pH of four will dissolve calcium phosphate, the stuff our 52 00:03:18,840 --> 00:03:22,280 Speaker 1: tooth enamel is made of. We consume lots of things 53 00:03:22,320 --> 00:03:26,000 Speaker 1: with a lower pH than that, vinegar, soda, citrus, juices, 54 00:03:26,040 --> 00:03:29,520 Speaker 1: and wine. You know how soda dissolves rust, Well, it 55 00:03:29,520 --> 00:03:31,560 Speaker 1: would do the same thing to our teeth if it 56 00:03:31,639 --> 00:03:35,560 Speaker 1: weren't for saliva. There actually isn't a lot known about 57 00:03:35,760 --> 00:03:40,640 Speaker 1: unstimulated saliva because it's difficult to collect, but it's always 58 00:03:40,680 --> 00:03:44,440 Speaker 1: flowing in the background. It's pretty viscous and stringy because 59 00:03:44,480 --> 00:03:48,200 Speaker 1: of a long chain of amino acids called musans. This 60 00:03:48,400 --> 00:03:53,080 Speaker 1: stickiness is what lets unstimulated saliva form a protective film 61 00:03:53,160 --> 00:03:56,240 Speaker 1: on the surface of our teeth. The proteins in there 62 00:03:56,240 --> 00:03:59,680 Speaker 1: both remineralize the enamel of our teeth and trapped back 63 00:03:59,720 --> 00:04:03,120 Speaker 1: to your which is swallowed and destroyed in the fiery 64 00:04:03,200 --> 00:04:07,200 Speaker 1: pits of our stomach acids. Speaking of stomachs, saliva is 65 00:04:07,520 --> 00:04:11,280 Speaker 1: hugely important to our digestion. It moistens dry food, and 66 00:04:11,400 --> 00:04:14,560 Speaker 1: like I mentioned earlier, it's saliva that starts breaking down 67 00:04:14,600 --> 00:04:18,359 Speaker 1: starch so we can eat it. It also helps slide 68 00:04:18,400 --> 00:04:21,360 Speaker 1: that food right down your esophagus and into your belly. 69 00:04:21,640 --> 00:04:25,400 Speaker 1: And most importantly, saliva alters the taste of foods, making 70 00:04:25,440 --> 00:04:29,080 Speaker 1: them more palatable. That's right. The bacteria in saliva is 71 00:04:29,120 --> 00:04:32,799 Speaker 1: what brings out the rich flavor and wine onions, peppers, 72 00:04:32,800 --> 00:04:37,360 Speaker 1: and more, and it even turns odorless compounds in fruit 73 00:04:37,480 --> 00:04:43,279 Speaker 1: and vegetables into much more aromatic chemicals called fields. Some 74 00:04:43,520 --> 00:04:46,719 Speaker 1: researchers even speculate that we could use the compounds in 75 00:04:46,839 --> 00:04:50,680 Speaker 1: spit to flavor food in our kitchen when it's not 76 00:04:50,839 --> 00:04:54,520 Speaker 1: digesting and making things taste great. Saliva is also a 77 00:04:54,640 --> 00:04:58,480 Speaker 1: lethal killer of germs. The wonder of saliva is that 78 00:04:58,520 --> 00:05:02,920 Speaker 1: it's both full of bacteria and an anti microbial assassin. 79 00:05:03,279 --> 00:05:06,320 Speaker 1: In fact, spit is so good at cleaning some art 80 00:05:06,360 --> 00:05:11,240 Speaker 1: conservators use it on fragile surfaces instead of chemical solutions. 81 00:05:11,600 --> 00:05:15,240 Speaker 1: This is because saliva has anti clumping properties that keep 82 00:05:15,279 --> 00:05:19,640 Speaker 1: bacteria from forming colonies on our teeth and gums. Proteins 83 00:05:19,680 --> 00:05:23,920 Speaker 1: called his statins not only hunt down bacteria and kill them, 84 00:05:24,240 --> 00:05:27,000 Speaker 1: but also have been shown to speed up the healing 85 00:05:27,080 --> 00:05:30,560 Speaker 1: process of wounds inside the mouth. Seriously, this is some 86 00:05:30,640 --> 00:05:35,880 Speaker 1: wolverine style regeneration. Here, wounds that take several weeks to 87 00:05:35,960 --> 00:05:39,480 Speaker 1: heal in our skin disappear within a week in our mouth. 88 00:05:39,960 --> 00:05:43,400 Speaker 1: In some cultures, a mother will even spit in her 89 00:05:43,440 --> 00:05:47,000 Speaker 1: infant's mouth to teach their immune system how to produce 90 00:05:47,040 --> 00:05:52,360 Speaker 1: antibodies and destroy pathogens. Because of all the antibodies already 91 00:05:52,480 --> 00:05:56,360 Speaker 1: in the mother saliva, this introduces the infant to bacteria 92 00:05:56,520 --> 00:06:00,200 Speaker 1: without getting them sick. Finally, did you know that our 93 00:06:00,200 --> 00:06:03,840 Speaker 1: saliva contains our entire genetic blueprint. If you're trying to 94 00:06:03,880 --> 00:06:07,000 Speaker 1: get away from a crime scene, don't spit on anything 95 00:06:07,040 --> 00:06:09,760 Speaker 1: because so many cells from the inside of your cheeks 96 00:06:10,120 --> 00:06:14,200 Speaker 1: slough off into saliva. It only takes half an eye 97 00:06:14,240 --> 00:06:17,880 Speaker 1: dropper worth of spit to sample your DNA. You can 98 00:06:17,960 --> 00:06:20,920 Speaker 1: even take a sample yourself, send it in the mail, 99 00:06:21,120 --> 00:06:24,679 Speaker 1: and get your own genetic information. This includes health data 100 00:06:24,839 --> 00:06:29,239 Speaker 1: like your susceptibility to certain diseases, so in the future, 101 00:06:29,440 --> 00:06:34,560 Speaker 1: scientists hope to catalog every single salivary protein. It's possible 102 00:06:34,800 --> 00:06:38,480 Speaker 1: that saliva could even replace blood for testing things like alcohol, 103 00:06:38,720 --> 00:06:43,560 Speaker 1: illegal drugs, and HIV antibodies. Some even theorize that your 104 00:06:43,600 --> 00:06:50,039 Speaker 1: body could dispense medications automatically by modifying the salivary glands genetically. 105 00:06:54,800 --> 00:06:56,800 Speaker 1: Check out the brain stuff channel on YouTube, and for 106 00:06:56,880 --> 00:06:59,279 Speaker 1: more on this and thousands of other topics, visit how 107 00:06:59,320 --> 00:07:14,240 Speaker 1: stuff works dot com.