WEBVTT - How Does the Skin Barrier Work? 0:00:01.840 --> 0:00:07.920 Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff. Lauren 0:00:07.960 --> 0:00:13.080 Bobelbam here. If you've ever watched a medieval era drama 0:00:13.320 --> 0:00:17.160 or fantasy, you may have marveled at the elaborate armor 0:00:17.239 --> 0:00:22.000 that characters wear into battle. Made of plates or scales 0:00:22.120 --> 0:00:25.640 or mail, armor is built to protect the wearer from 0:00:25.760 --> 0:00:30.480 specific types of weapons and attacks. It may not feel 0:00:30.520 --> 0:00:33.279 like it, but your skin is also a type of 0:00:33.320 --> 0:00:38.600 incredibly effective armor built to fend off specific attacks. It's 0:00:38.680 --> 0:00:41.960 not great at handling swords or arrows, but to be fair, 0:00:42.200 --> 0:00:47.920 those are relatively new inventions, far older threats like microbes 0:00:47.960 --> 0:00:51.720 and ultraviolet light. That's where our skin is a hero. 0:00:53.120 --> 0:00:55.319 It's our first line of defense as we move through 0:00:55.320 --> 0:00:58.840 the world, though it operates more like the manned walls 0:00:58.840 --> 0:01:03.520 of a castle than armor on a knight. Specialized cells 0:01:03.560 --> 0:01:07.840 and surrounding structures form a physical barrier between you and 0:01:08.200 --> 0:01:11.280 everything that's not you, sort of like a castle wall, 0:01:11.880 --> 0:01:15.160 and inside of that, an immune barrier stands at the 0:01:15.240 --> 0:01:18.600 ready like a castle's guard, to eliminate any threats that 0:01:18.680 --> 0:01:23.440 do make it through. But for our body's most visible organ. 0:01:24.000 --> 0:01:28.160 All of this happens on a microscopic level. So today 0:01:28.440 --> 0:01:31.399 let's delve into the skin barrier, how it protects us, 0:01:31.640 --> 0:01:35.840 and what can happen when something goes wrong. We've talked 0:01:35.840 --> 0:01:38.080 before on the show about the layers of the skin. 0:01:38.760 --> 0:01:43.200 The innermost layer, the hypodermis, provides structural support. It contains 0:01:43.280 --> 0:01:46.800 fat to insulate and cushion our underlying muscles and organs, 0:01:46.920 --> 0:01:49.720 plus blood vessels to get supplies to the middle layer, 0:01:49.880 --> 0:01:53.400 the dermis. The dermis contains all of the skin's equipment, 0:01:53.880 --> 0:01:57.880 nerve endings, sweat glands, pair follicles, and so on. All 0:01:57.920 --> 0:02:01.200 of that is sealed in and protected the outermost layer, 0:02:01.440 --> 0:02:06.120 the epidermis. The epidermis itself has two main layers, the 0:02:06.160 --> 0:02:08.680 inner of which is living, and the outer of which 0:02:08.800 --> 0:02:12.320 is dead. The dead skin cells of the outer layer 0:02:12.400 --> 0:02:15.280 are what we see and touch, and it's called the 0:02:15.320 --> 0:02:20.040 stratum cornium. The stratum corneum is often described as being 0:02:20.160 --> 0:02:23.240 like a brick wall, though luckily for us, a very 0:02:23.280 --> 0:02:26.880 flexible one, because it's made up of tough cells that 0:02:26.960 --> 0:02:30.079 are stacked and bound together with a kind of mortar 0:02:30.560 --> 0:02:36.440 of waxy, fatty lipids and some adhesive proteins. Those tough 0:02:36.480 --> 0:02:41.440 cells are called corneocytes. It's weird to think that their 0:02:41.639 --> 0:02:45.120 entire purpose in life is to die, but it's for 0:02:45.160 --> 0:02:48.399 the greater good of the organism. Because they're dead, they 0:02:48.480 --> 0:02:51.560 can't be infected by a virus or stopped from doing 0:02:51.639 --> 0:02:55.040 their job by bacteria. At their job is to sit there. 0:02:56.240 --> 0:02:58.799 They develop in the inner part of the epidermis, and 0:02:58.840 --> 0:03:01.360 as they're pushed to the out side, they die and 0:03:01.560 --> 0:03:07.480 flatten into sort of long, hardened envelopes containing keratin. Keratin 0:03:07.600 --> 0:03:10.200 is the protein that makes our hair and nails tough, 0:03:10.680 --> 0:03:14.960 and other things too, like feathers, hoofs, and horns. The 0:03:15.000 --> 0:03:19.200 etymology of the words keratin and corneocyte is actually related 0:03:19.280 --> 0:03:22.120 to the word horn. They all root back to early 0:03:22.200 --> 0:03:25.440 Indo European words for the hard and bony things that 0:03:25.480 --> 0:03:28.760 come off of an animal's skull. It's the same root 0:03:28.760 --> 0:03:33.480 where we get the word for the horn shaped cornucopia. Anyway, 0:03:34.320 --> 0:03:38.560 the tough corneocytes in your stratum corneum also contains stuff 0:03:38.600 --> 0:03:41.920 that can grab up molecules of water, which is good 0:03:42.040 --> 0:03:45.680 because ideally your outer skin should be dry. No one 0:03:45.760 --> 0:03:50.720 wants permanently moist skin, but not too dry. Having a 0:03:50.760 --> 0:03:53.400 bit of water in your skin keeps it pliable and 0:03:53.480 --> 0:03:57.920 prevents the skin from cracking. And as I said, the 0:03:58.000 --> 0:04:01.200 corneocytes are bound together with the sort of mortar made 0:04:01.240 --> 0:04:04.400 up of sticky proteins and a bunch of lipids, which 0:04:04.440 --> 0:04:09.320 are fatty or waxy substances. This is great because a 0:04:09.520 --> 0:04:13.160 it holds the corneosytes tightly in place, and also b 0:04:13.840 --> 0:04:18.240 it's what makes our skin more or less waterproof. Oil 0:04:18.240 --> 0:04:21.479 and water repel each other, so the oily lipids help 0:04:21.560 --> 0:04:25.719 make our skin impermeable to water. The stratum cornium is 0:04:25.920 --> 0:04:28.880 essentially the reason that all of the water that makes 0:04:28.960 --> 0:04:31.360 up some sixty percent of our body and makes our 0:04:31.480 --> 0:04:36.200 organs work stays in our body and doesn't just evaporate out. 0:04:36.880 --> 0:04:41.040 It also prevents many potentially harmful water based liquids, including 0:04:41.080 --> 0:04:45.440 ones that contain germs, from leaking into our body. Not 0:04:45.600 --> 0:04:48.160 too shabby for a stack of dead cells only some 0:04:48.279 --> 0:04:51.599 ten to twenty micrometers thick, which is about the thickness 0:04:51.640 --> 0:04:54.960 of one or two layers of plastic wrap. Even the 0:04:55.040 --> 0:04:58.080 fact that the corneocytes are dead and thus can't be 0:04:58.200 --> 0:05:01.760 repaired when they wear out and therefore get sloughed off 0:05:01.760 --> 0:05:05.320 and replaced on a continual basis. That's a feature, not 0:05:05.400 --> 0:05:09.080 a bug. This way, any microbes that might take up 0:05:09.120 --> 0:05:12.599 residents in or around your corneocytes get slothed right off 0:05:12.640 --> 0:05:17.200 with them. In healthy skin, your stratum cornium totally replaces 0:05:17.240 --> 0:05:21.279 itself about once a month. The cells in the layer 0:05:21.400 --> 0:05:24.800 of the epidermis directly beneath the stratum cornium where the 0:05:24.800 --> 0:05:29.520 corneocytes develop, are also tightly junctured together, adding to the 0:05:29.600 --> 0:05:33.720 security of the physical barrier of our skin. Plus they 0:05:33.760 --> 0:05:40.240 release some helpfully antimicrobial molecules. Because as impressive as this 0:05:40.360 --> 0:05:44.279 physical barrier is, it is then and delicate and pretty 0:05:44.279 --> 0:05:48.800 easily scratched or pierced. That's why we have an immune 0:05:48.920 --> 0:05:52.799 border guard lying in wait just inside our skin's castle wall. 0:05:53.960 --> 0:05:56.839 Our immune system is really complicated, and I am not 0:05:57.040 --> 0:06:00.400 a medical professional, y'all, I was an English major. But 0:06:00.720 --> 0:06:05.520 very basically, your epidermis and dermis each contain some specialized 0:06:05.560 --> 0:06:10.800 immune cells that can contain and neutralize any invaders. They 0:06:10.800 --> 0:06:13.800 can also call in backup from other immune cells that 0:06:13.880 --> 0:06:18.040 exist throughout the body via chemical signaling that creates inflammation. 0:06:19.480 --> 0:06:21.200 If you think about the last time you got a 0:06:21.279 --> 0:06:23.880 scrape or a cut, you may have noticed that it 0:06:23.960 --> 0:06:28.040 got reddish or purplish and puffed up a bit. That 0:06:28.120 --> 0:06:31.640 inflammation may be uncomfortable, but it's our body's way of 0:06:31.720 --> 0:06:34.560 getting extra supplies to the site of an injury to 0:06:34.720 --> 0:06:39.799 prevent infection and heal everything up. Once that backup arrives 0:06:39.839 --> 0:06:42.560 to the site, all of the immune cells work together 0:06:42.640 --> 0:06:46.560 inside the skin to clear out invaders and cellular debris. 0:06:47.600 --> 0:06:50.920 When they're done, other cells call off the inflammation and 0:06:51.120 --> 0:06:54.840 everything goes back to normal. The physical barrier is restored, 0:06:55.120 --> 0:06:57.960 and the immune barrier steps down from red alert to 0:06:58.080 --> 0:07:03.680 a state of watchful preparedness. Of course, this is assuming 0:07:03.720 --> 0:07:08.279 that everything is operating normally. The creation of the physical 0:07:08.320 --> 0:07:11.840 barrier and the responses of the immune barrier are both 0:07:11.920 --> 0:07:17.120 extremely complex processes, and unfortunately, any number of things can 0:07:17.200 --> 0:07:20.840 upset them, either from the outside in or the inside out, 0:07:21.480 --> 0:07:27.080 or both. Just for example, that lipid mortar around corneocytes 0:07:27.320 --> 0:07:30.640 gets produced by the corneocytes themselves as they develop into 0:07:30.640 --> 0:07:34.560 their final form. So if anything changes in the cells 0:07:34.600 --> 0:07:39.200 developmental process, say if it moves too fast, that doesn't 0:07:39.240 --> 0:07:42.800 just disrupt how those corneocyte bricks stack up. It can 0:07:42.840 --> 0:07:46.280 also disrupt the formation of the mortar around them, and 0:07:46.440 --> 0:07:49.680 having too much or too little of any component in 0:07:49.720 --> 0:07:52.800 the bricks or the mortar changes the way that the 0:07:52.840 --> 0:07:58.280 wall holds together. From the outside, our skin can become 0:07:58.360 --> 0:08:01.080 brittle if our environment is too dry, but it can 0:08:01.080 --> 0:08:05.360 also get flaky if it's too humid. Exposure to irritating 0:08:05.480 --> 0:08:10.720 or allergenic substances can cause an overactive immune response. Getting 0:08:10.760 --> 0:08:13.520 too much sun does cellular damage that your skin has 0:08:13.560 --> 0:08:17.840 to repair, which when repeated, will reduce cellular function over time. 0:08:18.920 --> 0:08:21.840 Even our mental health and stress levels are tied into 0:08:21.880 --> 0:08:25.960 how our organs function, and our skin certainly is an exempt, 0:08:26.120 --> 0:08:28.360 as anyone who's ever gotten a ZiT before a big 0:08:28.400 --> 0:08:32.080 event can tell you. From the inside, there are a 0:08:32.200 --> 0:08:35.680 number of diseases and conditions that muck about with some 0:08:35.840 --> 0:08:40.559 part of the skin barrier's upkeep, resulting in itchiness, flakiness, 0:08:40.679 --> 0:08:45.480 or other discomfort at best. For example, we talked recently 0:08:45.520 --> 0:08:48.320 on the show about psoriasis, a condition in which a 0:08:48.360 --> 0:08:52.080 combination of skin cell overgrowth and immune system freak out 0:08:52.400 --> 0:08:56.439 creates uncomfortable, scaly, or discolored patches that come and go, 0:08:56.920 --> 0:09:01.120 triggered by those outside stressors that I mentioned. If you 0:09:01.240 --> 0:09:05.400 or someone in your care experiences chronic skin barrier disruptions 0:09:05.400 --> 0:09:08.440 that result in that kind of issue. Definitely talk to 0:09:08.440 --> 0:09:11.920 a medical professional about the best way or ways to proceed. 0:09:12.720 --> 0:09:15.400 There are lots of topical and systemic treatments that can 0:09:15.440 --> 0:09:18.280 help control activity in the immune system or the skin, 0:09:18.760 --> 0:09:20.599 and a healthcare provider will be able to help you 0:09:20.640 --> 0:09:24.920 with the diagnosis and a plan. That being said, even 0:09:25.000 --> 0:09:28.520 finding a regimen that keeps quote unquote normal skin happy 0:09:28.720 --> 0:09:31.840 can be a challenge because the skin barrier is so 0:09:32.000 --> 0:09:35.559 complex that its exact functions are really pretty unique to 0:09:35.600 --> 0:09:40.040 all of us, and it changes over time. Simply getting 0:09:40.040 --> 0:09:43.400 older means that our skin structure thins and becomes less 0:09:43.400 --> 0:09:47.400 elastic and develops a different balance of immune cells. These 0:09:47.520 --> 0:09:51.000 changes in our skin barrier make us more susceptible to infections. 0:09:52.240 --> 0:09:55.960 A specialist like a dermatologist or esthetician may be able 0:09:56.000 --> 0:09:59.200 to help find exactly the right kind of moisturizer and 0:09:59.360 --> 0:10:03.880 other products for you, but the top level advice is 0:10:03.920 --> 0:10:06.760 to prevent skin barrier damage in the first place by 0:10:06.800 --> 0:10:10.560 treating your skin gently, protect it if you're going to 0:10:10.600 --> 0:10:13.480 be handling harsh chemicals or going out in the sun, 0:10:13.960 --> 0:10:18.240 and don't over cleanse after all, if your skin is 0:10:18.280 --> 0:10:21.560 your castle, your first duty is to respect such a 0:10:21.559 --> 0:10:29.720 grand structure. Today's episode is an original written by me. 0:10:30.640 --> 0:10:33.760 Brain Stuff is production of iHeartRadio, produced by Tyler Klang. 0:10:34.320 --> 0:10:37.400 Four more podcasts my heart Radio, visit the iHeartRadio app, 0:10:37.559 --> 0:10:50.400 Apple Podcasts, or wherever you listen to your favorite shows.