0:00:03 > 0:00:06Are you ready for our Ouch! Snips? Snip!Ouch!Exactly!
0:00:18 > 0:00:22Well, it may look pretty hairy, but it's actually from your tongue!
0:00:22 > 0:00:24Take a look at this.
0:00:25 > 0:00:28This is an MRI scan of my tongue as I'm speaking,
0:00:28 > 0:00:31and you can see it's pretty huge.
0:00:31 > 0:00:34But speaking isn't the only thing you need your tongue for.
0:00:34 > 0:00:36One of the best things it does is help you taste.
0:00:36 > 0:00:40Your tongue is covered in small hairlike projections,
0:00:40 > 0:00:45as I'm going to show you. Right, Xand, open your mouth nice and wide.
0:00:45 > 0:00:48Eurgh! Not hair like that! I said hairlike projections!
0:00:48 > 0:00:50You can't see them with your naked eye.
0:00:50 > 0:00:54Take another look at this super close-up of your tongue.
0:00:54 > 0:00:56This red blob is called the papilla.
0:00:56 > 0:00:59Your taste buds sit on the side of it, and they contain tiny
0:00:59 > 0:01:03hairlike projections called microvilli to help you taste.
0:01:03 > 0:01:06And if you look at your tongue, the bumps you can see are the papillae.
0:01:08 > 0:01:10And the more papillae you have on your tongue,
0:01:10 > 0:01:14the more taste buds you have and the more sensitive to taste you are.
0:01:14 > 0:01:18And you have more of them than we do.Because we're doctors!No, Xand!
0:01:18 > 0:01:19Because we're adults!
0:01:19 > 0:01:24We have around 5,000 covering our tongues, but you have 10,000.
0:01:24 > 0:01:25That's twice as many.
0:01:25 > 0:01:28And to prove it, Chris, I've brought in a sample.
0:01:29 > 0:01:34This sample is nine years old. This isn't a sample. It's a child!
0:01:34 > 0:01:37Anyway, the point is, we're going to compare Chris' papillae with
0:01:37 > 0:01:42the sample's, but first I need to cover your tongues in blue food dye.
0:01:42 > 0:01:47The blue dye will show up all the papillae.And now, the sample.
0:01:47 > 0:01:50I have a name, you know, and it's Hermione.A very noisy sample!
0:01:50 > 0:01:51Give me your tongue!
0:01:54 > 0:01:55Nice blue tongue, Hermione!
0:01:55 > 0:01:58Xand is putting a glass slide on both our tongues to make it
0:01:58 > 0:02:00easier to count the papillae.
0:02:00 > 0:02:03Chris' papillae are those little pale dots right there.
0:02:04 > 0:02:06And these are Hermione's.
0:02:06 > 0:02:09You can see that there's way more on her tongue,
0:02:09 > 0:02:11and that means more taste buds.
0:02:11 > 0:02:12Good job, Hermione!
0:02:13 > 0:02:16As we get older, your taste buds deteriorate
0:02:16 > 0:02:19and they aren't replaced, which is why you will be much more
0:02:19 > 0:02:23sensitive to strong flavours like garlic than your mum or dad.
0:02:23 > 0:02:26There are certain things, though, like a cold,
0:02:26 > 0:02:28that can play havoc with everybody's sense of taste.
0:02:28 > 0:02:31But why would having a bunged-up nose affect your taste?
0:02:31 > 0:02:33Well, we're going to show you.
0:02:36 > 0:02:41Xand, meet Mr Bigmouth.Hello! Argh! You've cut him in half!
0:02:42 > 0:02:44Now, when you eat food, odour molecules are released
0:02:44 > 0:02:48and swirl around your mouth, but also right up into this.
0:02:48 > 0:02:51This is the passage that connects your mouth to your nose.
0:02:51 > 0:02:54And right up here, at the back of your nose,
0:02:54 > 0:03:00are lots of sensors called olfactory receptors, which sense and identify
0:03:00 > 0:03:02different odour or smell molecules
0:03:02 > 0:03:04and tell your brain what it is you're tasting.
0:03:04 > 0:03:09So, to show you this, we're going to use an equally oversized bit of kit.
0:03:10 > 0:03:12The smell molecule blower thingy.
0:03:12 > 0:03:14Also, we'll need our safety equipment
0:03:14 > 0:03:17and these polystyrene balls to represent
0:03:17 > 0:03:19those smell or odour molecules.
0:03:19 > 0:03:21Three, two, one... Blow!
0:03:23 > 0:03:26The smell molecules in food are released naturally as you chew.
0:03:26 > 0:03:28Wow! That worked really well!
0:03:29 > 0:03:32You can see how the smell molecules race through
0:03:32 > 0:03:35the back of the mouth and up the tube connecting it to the nose
0:03:35 > 0:03:38and right onto the olfactory receptors, which instantly
0:03:38 > 0:03:41recognise the smell and tell your brain what you're tasting.
0:03:41 > 0:03:44And your olfactory receptors can also protect you
0:03:44 > 0:03:47because they can tell if something is bad before you eat it.
0:03:47 > 0:03:50As soon as they whiff something like off milk,
0:03:50 > 0:03:52they alert your brain so you know not to eat it.
0:03:52 > 0:03:56But, Xand, what would happen if Mr Bigmouth got a cold?
0:03:56 > 0:03:59That would be disgusting! We're going to need a lot of snot!
0:04:02 > 0:04:06We're smearing our snot inside the passages of our giant mouth
0:04:06 > 0:04:09and nose, just like when you have a cold.
0:04:09 > 0:04:13Let's see what happens now that Mr Bigmouth has got a big cold.
0:04:13 > 0:04:14You ready?BOTH:Go!
0:04:21 > 0:04:25Look. This time, the odour molecules are getting stuck in the snot.
0:04:25 > 0:04:29They aren't getting anywhere near the olfactory receptors,
0:04:29 > 0:04:31and that means no taste.
0:04:31 > 0:04:35Yeah, Mr Bignose wouldn't be able to taste anything at all.
0:04:35 > 0:04:38Except for that one tiny polystyrene ball.
0:04:39 > 0:04:41So we've shown you that, like Hermione's tongue,
0:04:41 > 0:04:44you've got twice the number of taste buds as us,
0:04:44 > 0:04:46or your mum and dad, or any adult.
0:04:46 > 0:04:49But as good as your tongue is, you also need your nose
0:04:49 > 0:04:51if you really want to savour a flavour.
0:04:51 > 0:04:53SNEEZING
0:04:53 > 0:04:55See you next time! Bye!Bye!
0:04:55 > 0:04:59Bye.Bye.Bye!Bye.Bye!
0:05:00 > 0:05:01NO SOUND