From Your Head to Your… Anus: The Truth About Hair | Compilation

[Music] hair whether you've got a lot of it or absolutely none it's one of those things that all of us have thought about at some point and we've ended up with some questions like why does it change color why does it disappear and yes the big one why is butt hair even a thing we've covered all of this and more over the years and now from your head to your toes we're putting it all together let's start at the top literally whether you're working on your thesis adjusting to a new job or just dealing with whatever life is these days you've probably run into the rumors about gray hair specifically that stress can make you go gray it seems fair enough given how much other stuff stress does to your body but is there any truth to it here's olivia with the answer we've all seen those comparison photos some president starts off with a full head of dark hair and a few years later they're totally gray but stress doesn't really turn your hair white at least not the hair already on your head it can help reveal gray hairs though by increasing turnover and scientists think it might just speed up the graying process a little too each hair gets its color from melanin a pigment made by specialized cells called melanocytes in hair follicles you can have gray or white hairs because the hair itself which is mostly a colorless protein called keratin is manufactured by different specialized cells in the follicle which are called carotenocytes and they tend to live longer than the pigment producing ones so hairs can keep growing shedding and growing anew even if those little pigment factories have stopped production how long your melanocytes last and therefore when you go gray is mostly determined by your genetics but your head doesn't turn white the second some of those cells die since the follicles can't alter hair that's already grown gray hairs don't start to show until the old colorful hair has fallen out which usually happens every few years but if something makes your hair fall out faster like i don't know being massively stressed out then it might seem like you're suddenly graying chronic stress is known to trigger telogen effluvium a condition where a hair follicle jumps ahead to the final stages of its life cycle and the hair attached to it falls out so instead of lasting years hairs can fall out within a few months of a stressful event the new hair starts growing again right away so it doesn't cause baldness and it doesn't affect melanocytes so for young people the hair that falls out grows back its normal color but if you happen to be at the age where the next hairs in line would be gray anyway it can speed up that turnover it's not that the stress turned your hair gray it just bumped your gray hairs to the front of the line that said there is some research that suggests stress might make you go gray sooner that's because stress can increase levels of free radicals atoms are molecules that have an unpaired electron which makes them unstable and very reactive they basically try to steal an electron from anything they run into which messes with key components of cells a 2006 study found that too many free radicals can prematurely age cells because of their toxic effects on dna or even kill the cells outright and that includes melanocytes other things known to increase free radicals in your body like smoking also happen to be associated with premature graying but so far no one has conducted a controlled experiment to conclusively demonstrate the connection between stress free radicals and the sudden appearance of gray hairs so stress might make you go gray or it might just reveal how gray your hair already is well that's kind of encouraging at least although i wouldn't mind a cool white streak in my hair someday regardless of what color your hair is though you've likely experienced the joys of frizz or at least if you have relatively long hair when it's humid out hair just puffs way out there turning into a staticy mess but weirdly enough there's something we can learn about the atmosphere because of it here's one from stefan you know what they say it's not the heat it's the humidity and that's extra true if your hair is the frizzy type the higher the humidity the more prone some of us are to a frizz castrophy and it all has to do with how water interacts with the proteins in our hair the really weird thing though is what hair has been able to teach us about atmospheric water frizz is what you get when individual strands of hair change shape and stop matching the neighboring strands this can mean getting curly wavy or otherwise infuriatingly irregular freezing has to do with hair's composition hair is made up of a long fibrous protein called keratin bundled layer upon layer in an elaborate structure the keratin molecules stay together through a combination of strong and weak chemical interactions the real beefy chemical bonds are called disulfide bonds in which sulfur atoms from neighboring protein strands join together in a pretty tight hold and the weaker interactions are what are known as hydrogen bonds hydrogen bonds aren't true chemical bonds rather they're a weak attraction between a slight positive charge and a slight negative charge for hair the hydrogen bonding happens between keratin molecules and water molecules when a water molecule bonds to two different keratins it can help hold them together to an extent but that hold can be easily broken or changed and when more water enters the picture it can change how keratin sticks together getting your hair wet can break previous hydrogen bonds and form new ones resulting in a new shape to your hair and when your hair dries in a certain shape it tends to stay which is why going to bed with your hair wet is asking for epic bed head when there's lots of water in the air in the form of high humidity the changes to our keratin molecules are more unpredictable frizz occurs when water is absorbed into dry hair in different areas at different rates some strands of hair may absorb water into the center while others may absorb less or none at all causing differences in swelling that affect hair shape alternatively the higher moisture may cause some strands to form so many hydrogen bonds around the outer layers that the hair folds back on itself forming curls and the water absorption is pretty random no two adjacent hairs respond to airborne moisture the same way resulting in the frizzy mess that we find so frustrating they all get bent out of shape differently but the amount of water a hair absorbs is ultimately still proportionate to the relative humidity like it's predictable enough to be useful for making measurements measuring humidity was a goal of scientists back in the day who wanted to know more about what caused rain and how predictable various weather phenomena could be enter the hygrometer a device for measuring relative humidity one of the first hygrometers was made in 1783 by horus benedict disosur and his worked using human hair this may seem weird and kind of gross but it's both effective and something you can try for yourself because dry hair will absorb atmospheric moisture you can reliably observe a long strand of hair to change shape as humidity changes all you have to do is fix one end of a clean deoiled strand of hair in place and hang a weight from the other end to keep it stretched then you can observe the length of the hair changing as humidity increases or decreases the proteins coil and uncoil as hydrogen bonds form and break all as a function of how much water is in the air so the resulting variation in the strand's length is proportionate to the humidity in the air you can even calibrate relative humidity by using a hair dryer to simulate zero percent and a wet rag for a hundred percent allowing you to get a sense of how far between those two extremes the air is on any given day so while it might be a seasonal annoyance at least frizz has some practical applications i mean knowing that you can study humidity with your hair probably won't help you the next time it's muggy but at least frizzy hair isn't 100 bad now when it comes to the hair on our heads there's one other big question why do people lose it i mean you might come into the world and grow a full thick head of hair but then you hit 30 or 50 or 70 and someone can suddenly see their reflection in your scalp we've talked about that one too and how some treatments try and fix it here's one from hank just another fun part of getting older as people age many of them start to lose their hair why it turns out it's complicated otherwise we would have fixed it by now because it's basically the holy grail of beauty but lots of different factors affect whether or not you end up with a shiny bald head but mainly it has to do with two things hormones and genetics hormones are involved because they affect how your hair grows more specifically you can blame testosterone because balding happens when hair follicles turn it into dihydrotestosterone or dht scientists don't know exactly why but dht makes certain hair follicles start to shrink as they get smaller their hair gets thinner and eventually the follicle stops producing hair entirely males typically have plenty of testosterone which explains why balding affects biosex males more than females in what's known as male pattern baldness hair loss starts at the temples in the top of the forehead and at the top of the scalp eventually the receding hairline meets the growing bald patch but biosex females produce testosterone too just a lot less of it and they make enough estrogen to mask its effects after menopause estrogen production slows but they're still producing about the same amount of testosterone so that's when the hair starts to get thinner in female pattern baldness it's more of an evenly distributed thinning of the hair across the scalp without much of a receding hairline so how do you figure out whether hair loss is in your future well that is more complicated and there's a lot that we still don't know mainly it seems to be tied to genetics and researchers have pinpointed a few different genes that might be involved some of these genes are on the x chromosome which explains why males are so much more likely to go bald than females males get only one x chromosome so whatever version of the gene they inherit on that chromosome is gonna be expressed females on the other hand have 2x chromosomes so there's more of a chance that they'll inherit a non-balding version of a gene from one of their parents but studies have shown that there are other genes on non-x chromosomes involved too like one genetic variant on chromosome 20 which made males seven times more likely to go bald but for some reason doesn't seem to influence whether females experience hair loss so there are a lot of different pieces to this balding puzzle which is why we haven't figured it out yet but if you don't like the new look there are some drugs that can help finasteride for instance works by blocking production of dht and minoxidil both increases blood flow to hair follicles and widens them helping hair grow of course you could also just embrace your newfound resemblance to jean-luc picard he did pretty well for himself all right now on to the rest of the body because although it's not always immediately obvious we are covered in little hairs we're pretty bald compared to most other mammals and there are various ideas about why but overall we have dense hair in just a few spots including our heads faces armpits and nether regions and those hairs are also different like the hair on your head can grow to be meters long but your armpit hair will stop after a few centimeters why here's another one from hank you're probably quite happy that your armpit hair isn't dragging on the floor so it's good that there's a system to prevent that but what is that system us humans grow hair all over our bodies except on our palms and the soles of our feet but some of it like leg hair stops growing while the hair on our heads just seems to grow out forever that's because every hair on your body goes through the same cycle growing for a while and then falling out but each type of hair spends a different amount of time growing and grows at a different speed every hair begins the same way in a phase of the cycle called anagen during antigen blood flow starts to ramp up at the base of the follicle feeding oxygen to specialized stem cells these cells begin rapidly dividing and producing keratinocytes which form the root of the hair as the expanding mass of keratinocytes is pushed toward the surface of the skin the cells die releasing a protein called keratin which holds the strand of hair together eventually that strand pops out of your skin so the visible part of the hair is entirely dead which is why thankfully it does not hurt to get your hair cut though try explaining that to a three-year-old during anagen hair can grow up to one and a quarter centimeters every month depending on where it's located on your body the second phase is called catagen and lasts about two weeks here the blood supply is cut off at the bottom of the follicle which stops the production of new keratinocytes so for that particular hair the party is over the follicle then shrinks to about a sixth of its original size and then the existing hair strand is pushed closer to the surface the third phase is called telogen otherwise known as the resting phase where the follicle remains dormant for one to four months finally the hair is released or shed when the follicle dilates and starts the anagen phase again so how long a hair on your body gets depends on how long it's in the anagen phase and how fast it grows during that time the hair on your scalp for example stays an antigen for two to six years which is why it can grow so long other hair types like eyebrows and eyelashes and body hair have a short anagen phase only 30 to 45 days but they also grow much more slowly with eyebrows for instance growing only 4.2 millimeters every month this is my eyebrow close-up hey as for how your hairs know when to grow and when to stop that's something scientists are still trying to figure out it is known that genetics can lead to longer or shorter antigen phases in certain hair types the current thinking is that your hairs get their instructions by way of chemical growth signals from stem cells in the skin and considering how extremely inconvenient it would be for all of the hairs on your body and all mammals bodies to just continue growing forever it makes sense that there's a system for making sure they don't grow too long all right we couldn't make this episode without including one from the scishow hall of fame why you may wonder do we have butt hair i'll just let hank take it from here we've covered a lot of topics both trivial and profound and we work very hard to capture both our fascination and excitement as well as our deep desire to always get things right and over the last year you may have noticed a comment on we think every single scishow video asking us one question we have ignored this question long enough it is time we took it on leto johnny wants to know why does he have hair around his anus well johnny the reason we haven't answered you is because you know like despite the fact that everyone gets their own personal pocket-sized supercomputer and then we can send robots to mars and convert the entire face of the planet to human use we still do not really know why humans have butt hair and it may not surprise you to learn that not a whole lot of research has been done on the why part of this question about butt hair but a fair amount of study has gone into the medical problems that butt hair can cause for example pilonidal disease is a chronic skin infection caused by hairs that get embedded near the top of the butt crack which if you want to impress your doctor you can describe by its technical name the intergluteal cleft so as the owner of a butt yourself you probably know that butt hair does seem to have more downside than upside so given that what if any purpose does it serve well there are a few theories out there and maybe some enterprising scientists out there watching right now can do some research on them but here's what's been proposed theory number one butt hair exists because there's just no significant evolutionary pressure against butt hair sure it's sometimes inconvenient and depending on the moment in cultural history it might be considered unsightly but it appears that butt hair has never been a significant reason for one human not to make babies with another human it's important to keep in mind that not every bit of our physiology needs an evolutionary purpose so butt hair might just be another side effect of unintelligent design theory number two scent communication body odor definitely has a negative connotation in today's world but there's little doubt that communication through scent has played an important role in the evolution of humans after all that's likely why we have body hair in the same areas where we produce body odors the hair is there to hold on to sebaceous or oily secretions that have their own smell and are also consumed by bacteria that create even more smells since we all produce different smell compounds and all have our own microbiomes each individual human actually smells different and if our early human ancestors were anything like other animals and they probably were their personal smell probably helped with everything from broadcasting territorial rights to attracting mates but here then maybe just another way our oldest human ancestors enhanced their smell profiles theory number three friction in addition to giving off smells humans have also always done a great deal of walking and running and skin rubbing on skin especially in areas where that skin may be moist and dirty can cause irritation rashes and even serious debilitating infection it's even possible that those sebaceous or waxy secretions that help produce body odor are held in place by body hairs to provide an added benefit acting like a kind of natural anti-chafing cream now this theory of the one that we've talked about is most appealing to me personally but it's very difficult to test because shaving or otherwise removing butt hair and then having someone run 20 miles on a treadmill is not a good experimental design because there's no way to know whether any irritation is caused by the lack of hair or whatever technique was used to remove the hair none of which sound fun to me but i have come up with an alternative experimental design that i like quite a lot just interviewing a few hundred runners about how much they need to worry about butt chafing and then measure the density of their anal plage to see if there's any correlation between whether they chafe and how hirsute their butts are which is not an experiment that i want to do personally but if there's an expert out there in anatomy and physiology who's up for tackling this prickly problem please take it on and if you get any useful data definitely let us and leto johnny know how it went for the record we made that video in 2016 and have yet to hear from any researchers but if you're out there we're still interested in the meantime well at least you have something to think about on your next trip to the bathroom thanks to everyone who's helped us make these episodes over the years whether you're a viewer or a full-out patron scishow exists because of your curiosity about the world and if you like this you'll probably also like our podcast scishow tangents it's hosted by some of the smart talented people who've made scishow happen and it features mind-blowing facts science poetry and a lot of laughter you can find it wherever you get your podcasts

Channel: SciShow

Views: 413,839

Rating: 4.9184422 out of 5

Keywords: SciShow, science, Hank, Green, education, learn, Hair, Compilation, Will Stress Really Make You Go Gray?, Why Does Hair Get Frizzy When It’s Humid?, Why Do People Go Bald?, How Does Hair Know When to Stop Growing?, Why Do We Have Butt Hair?, Age, Old, Grow, gray hair, stress, frizzy, bald, butt, body, hair cut

Id: fUD8vXKAmyg

Length: 17min 46sec (1066 seconds)

Published: Wed Sep 09 2020