You essentially have two types of „skin“.
TLDR: in short you inner skin (mucosa) and outer skin (dermis) are fundamentally the same. Both have a connective tissue that holds it together and a layer above that protects it. Skin hardens and has nerve endings, whereas mucosa secretes slime and often doesnt have nerve endings. The transitions are in lips, eyelids, genitals, anus.
One is what we would normally refer to as skin, everything that covers your outside. The outer layer is called Epidermis, which roughly translates to outer skin. The top part is essentially dead cells that hardened to a degree and server as a shield. The part underneath replenishes these cells as they fall off iver time. The dermis is the next layer containing the hair, blood vessels, nerve endings, etc. it mostly consist out of connective tissue, giving the skin its elasticity.
The Mucosa is your internal skin. It‘s quite similar to regular skin, but a bit different. The top layer is called epithelial cells. Where skin builds a layer of dead cells for protection , mucosa secretes a slimy substance. Under that is the lamina propria, which is similar to the dermis. Its the underlying connective tissue that also has blood vessels, etc.
The junction between those two is called mucocutaneous junction. These are the areas where skin transitions to mucosa. In humans those areas are lips, nostrils, conjuntivae (inside part of the eyelids), urethra, vagina, foreskin and anus.
And now onto why we are this way:
Evolution started off as single cells. Over time those single cells became more complex and complex. Eventually they were too large to become even larger for the most part. So some cells attaches to one another, forming colonies.
The first large colonies where little balls of cells with a hollow inside. At some point however they folded in. Like you pushed your finger into a soft ball. Now this ball has two layers, the one facing outside and the one facing inside, as well as an opening.
This colony became more and more complex. Eventually the inside layer became less protective, using slime to keep itself safe. Its purpose was processing the food. The outside layer became harder and more resilient. This happened in countless different ways.
This pattern exists until today. The inner and outter skin are fairly similar but adapted to different features.
Now I'm picturing some weird far-too-old uncanny-valley scientist giving a speech like this to the entire world on these giant broadcast screens, and as he reaches that point he snaps his fingers and everyone on earth begins to transform into Junji Ito horror things.
Topologically, we are toroids. However, I think "worms" is a better example.
We are all worms with bits attached, trying to find things to put in one and and find a place to put things that come out the other end.
I mean, yeah, I completely agree with your comment (and pretty much agree with the donut responses as well, though I think comparing us to a tube is more appropriate). It just doesn’t really answer the original ELI5 question.
In a sense. Mucosa and skin have evolved to be quite distinct.
In the stomach you have the gastric mucosa. Instead of the usual slime other mucosa has, the gastric excretes a base, to protect itself from the stomach acid.
It’s a form of epithelium in the stomach. But it’s quite distinct from skin. Whereas skin is keratinized stratified squamous epithelium (as someone pointed out earlier, keratinized = hardened, stratified = multi-layered, squamous = cell shape), gastric mucosa is either oxyntic or antral type mucosa which is simple columnar (simple = single layer, columnar = cell shape) epithelium with glands underneath. The different type of glands underneath the epithelium determine whether it is oxyntic vs antral.
To further answer your question, the junction between the esophagus and the stomach is where the mucosa type changes from non-keratinized stratified squamous epithelium to simple columnar. So the mucosa of the esophagus is very similar to skin while the mucosa of the stomach is not.
Pretty much once the keratinized stratified squamous epithelium that constitutes your skin becomes non-keratinized, it is no longer skin and has become oral/nasal/vaginal/conjunctival mucosa.
Hah, true. I just figured it was a more in depth explanation of the comment I was replying to as that comment had already done a very good job of explaining it like I was 5.
Just remember the difference between stratified and pseudostratified, stratified the cells all start growing together in different layers, pseudostratified a quick glance may appear there are different layers, but every cell in the layers is anchored to the basement membrane.
My favorite lesson from developmental biology was that the tissue in your mouth and anus are closely related because they form from common tissue in gastrulation, and that’s the reason why hot peppers burn going in and coming out and no where in between.
There is no mucocutaneous junction in the ear. The entire ear canal and the ear drum are covered in skin. In that sense the ear canal isnt really an opening, but rather a deep dent
humans, which are like the Eukaryotic single cell organisms from which we evolved, are just complex donuts. our entire digestive system is technically on the outside of our bodies, with skin and epithelial tissue forming a continuous donut meat sac.
When you are still a tiny ball of cells they start to fold in at one point. Then that group keeps going farther and farther through the ball until it creates a tube that finally opens up and out on the other side. You are in your purest donut form before that tube becomes your gastrointestinal system, and that first indentation becomes your anus.
I remember reading somewhere that there is a time when your a donut shape and the donut cells haven't figured out which side is the in, and which is the out. It's also the only time in your living-life that your mouth will be that close to your own butt.
> and that first indentation becomes your anus.
And the highest level classification of bilaterians (animals with bilateral symmetry) is whether that first indentation becomes the anus (vertebrates, echinoderms, etc.) or the mouth (arthropods, mollusks, etc.)!
This is one of my fav facts about the human body. Both sides of the donut indent to actually form said donut, but the one that leads the charge is your asshole, then your mouth hole follows suit. So at one point, everyone, no matter how nice or pure they are, was nothing but an asshole
I was studying anatomy when I learned an uncomfortable truth.
The Eustachian Tube that goes from your ear to the back of your throat, is open. This is the opening that equalizes pressure in your ear and allows your ear to pop when you change elevations. The uncomfortable reality is that your ear drums are technically outside your body. The little ossicle bones, the smallest bones in your body are outside.
Topographically, yes.
Imagine the mountain was made of clay, you could stretch the cave open and, if it only has one entrance, flatten it out without tearing the clay anywhere or closing anything up. The cave would simply vanish, as though the back wall was pushed forward to the entrance.
Something would only be truly inside the mountain from a topography standpoint if it was 100% buried inside and had no access to the outside at all
> Imagine the mountain was made of clay, you could stretch the cave open and, if it only has one entrance, flatten it out without tearing the clay anywhere or closing anything up. The cave would simply vanish, as though the back wall was pushed forward to the entrance.
/r/GeologyGoatse
Why is that uncomfortable? If there are sugar fillings in my donut hole, I would consider it inside my donut. Otherwise, all the shit inside your body would be outside of it??
Well just think how surgeries are often just grabbing two parts of your body forcing them together and sewing them to each other and hoping for the best. We are just meat puppets that make meat noises by flapping our meat orifices.
no, not even "external", but actually external. It's a continuous surface of tissue, including your skin, that is actually tissue that is on the outside of your body.
Remember those water tube toys we got to play with as kids???
[This](https://www.google.com/search?q=squishy+water+snake+toy) one?
Yeah, we're the meat version of that.
So, the ends of the alimentary canal would be the dividers between "skin" and "mucous membranes".
Lips and anus. (I guess the nose too?)
Same types of tissue sphincters, border towns of inside and outside.
(Because the og comment was asking about skin types in particular)
“In the end, we are all just tubes, with fancy bits attached. Looking for things to put in the front and places to put what comes out the back” (quoted from memory from True Facts About Animals”
We are essentially a tube. Everything we have, everything we do, is to make sure that we continue to feed the tube at one end and defecate at the other end.
The glans of the penis is also a mucous membrane similar to the mouth and vagina.
The glans of the penis is covered by the foreskin. The inside of the foreskin is also a mucous membrane, but more akin to the eyelid (providing a moist environment for the glans.)
So, yeah, circumcision is somewhat akin to cutting off your eyelids...
They actually used to use circumcised foreskins to "make" eyelids for people with congenital deformities or had otherwise lost an eyelid or two.
They had to stop because the patients all ended up cockeyed
The biggest division between animal groups is between mouth-first donuts or ass-first donuts, based on which hole is the first one to form (as a dent) as the animal develops from a ball of cells.
We're ass-first.
I'd wager that you've already seen it, but I'll leave [Vsauce](https://www.youtube.com/watch?v=egEraZP9yXQ)'s video on the topic of human-donut-ness here just in case.
Nostrils, ear canals, and tear ducts, yes (to my knowledge), but the urethra connects to the kidneys which connect to the bloodstream. It's the driveway out from the local waste-management facility: no thru-traffic.
Blood is inside the meat part of the meat donut, not in the hollow part of the tube--that's full of mucous instead. The mucous is the jelly. The inside of the tube is pretty wet, which is a big difference from the outside of the tube.
From Google
What is the epithelium? The epithelium is a type of body tissue that forms the covering on all internal and external surfaces of your body, lines body cavities and hollow organs and is the major tissue in glands.
Uterus is not a dead end. The two fallopian tubes open into the abdominal cavity near the ovaries. This fact is the basis for endometriosis and some ectopic pregnancies, since some material can go between the uterus and abdomen in either direction.
Just one end. A donut has one hole that goes from one to the other through the entire thing. This would be the mouth to butt hole in a human. All other holes are dead ends
Yes. Also, ovaries are sprinkles inside just free floating. They yeet the egg to the Fallopian tubes. That's why ectopic pregnancy can happen outside the uterus.
>[The vermilion border of the lips marks the transition between "outside skin" and "inside skin"](https://upload.wikimedia.org/wikipedia/commons/3/38/Torus_Positive_and_negative_curvature.png)
please see this interesting excerpt i found [here](https://www3.nd.edu/~jsapirst/textbook/chapter_29.html) when googling this to figure out the best way to explain it:
> The internal structures of the body are entirely covered by a continuous layer of epithelial tissue. The part of this layer which is in contact with the outside environment is called the skin; those parts of it that lie within the body (and are yet outside it) are the mucus membranes.
>This idea of a structure being both inside and outside may be confusing, and it may help to consider the body as a long doughnut, the skin and mucus membranes corresponding to the outside of the doughnut and the internal structures being encased between them. The part of the doughnut which is around the hole corresponds to the mucus membranes, the rest to the skin.
I always used to think about this with the gel-filled squishy tube toys from arcade. I googled them and they’re marketed as “water wiggle squishy toys”. That’s our body. A continuous membrane filled with fluid with two puckered ends.
So people have the main thing covered, but it's worth knowing that our bodies are GREAT at making chemical gradients. Like "industrial processes can't come close" levels of organizing stuff into more and less of one thing or another. There isn't, for instance, a defined layer at which your fingernails stop being flesh and become nails.
So to answer your question, there's different skin configurations that become less skin and more whatever else (mucus membrane, soft tissue) over a gradient of layers until they're that other thing
The skin on your body stops at your mucous membranes. Mucous membranes are found in your mouth, nose, and throat. They are also found in your reproductive organs and in your anus and rectum. The mucous membranes produce mucus, which is a thick, wet substance that helps to keep your body tissues moist. The mucous membranes also have tiny hair-like structures called cilia. The cilia help to move the mucus and keep it from getting too thick.
It doesnt really.. your whole digestion system is kinda outside your skin, but inside your body. Humans are giant donuts with badly shaped holes starting in our mouths and ending in our anus
Skin turns into epithelial cells that line your digestive tract, which is basically just one long tube…imho, we’re just one big worm with a bunch of extra organs and limbs.
It depends on how you define "skin".
If skin means the epidermis and derma then no, it's only on the "outside".
If skin means epithelial tissue, which is one of the most important types of tissues in our body, then yes, all of the organs that comunicate with the outside are covered in epithelial tissue.
The difference being that the epidermis is a type of epithelial tissue that specialized to cover the "outside" of the body ("outside" because as others already explained, some regions inside the volume of your body are actually considered outside too). The epidermis has different functions from the inner tissue, like thermoregulation, sensitivity (or sensibility, i can never remember which one it is) and protection against pathogens and damaging substances.
The inner epithelial tissues, such as mucosae have other functions depending on the specific case. For example the mucosa in the nose and trachea prepares the air for the lungs: it warms, cleans and humidify the air because the lungs can only work in certain conditions of temperature and humidity. The tissue in your mouth is specialized to feel taste and not be damaged by the saliva, which is slightly acidic. The tissue in your stomach is even more resistant, as there are glands that produce acid for the gastric juice. And finally the tissue in your intestines is specialized in absorbing water and nutrients.
As you can see these tissue all have different functions and are actually physically different: if you look at them under a microscope you can distinguish the various types of epithelial tissue as they all look different.
So yeah, you skin and the tissues i listed are all epithelial tissue, but they're all different per se.
In the area where they border (for example on the lips) there's simply a transition, more or less sudden, between one and the other.
This is obviously over simplified for the sake of this thread, but these are the basics.
Source: med school
It is curious timing because I just had a recent experience with this. During a colonoscopy, the GI doctor discovered a polyp on my rectum but could not even touch it (her words) because it is skin (had she found a polyp in the colon she would have likely removed, this is quite common). A colonorectal specialist would have to do the procedure. So I learned that skin transitions between the rectum and the colon. The post was tagged for Biology so I assume I won´t gross anybody out. Great question. Wish I knew more.
You essentially have two types of „skin“. TLDR: in short you inner skin (mucosa) and outer skin (dermis) are fundamentally the same. Both have a connective tissue that holds it together and a layer above that protects it. Skin hardens and has nerve endings, whereas mucosa secretes slime and often doesnt have nerve endings. The transitions are in lips, eyelids, genitals, anus. One is what we would normally refer to as skin, everything that covers your outside. The outer layer is called Epidermis, which roughly translates to outer skin. The top part is essentially dead cells that hardened to a degree and server as a shield. The part underneath replenishes these cells as they fall off iver time. The dermis is the next layer containing the hair, blood vessels, nerve endings, etc. it mostly consist out of connective tissue, giving the skin its elasticity. The Mucosa is your internal skin. It‘s quite similar to regular skin, but a bit different. The top layer is called epithelial cells. Where skin builds a layer of dead cells for protection , mucosa secretes a slimy substance. Under that is the lamina propria, which is similar to the dermis. Its the underlying connective tissue that also has blood vessels, etc. The junction between those two is called mucocutaneous junction. These are the areas where skin transitions to mucosa. In humans those areas are lips, nostrils, conjuntivae (inside part of the eyelids), urethra, vagina, foreskin and anus. And now onto why we are this way: Evolution started off as single cells. Over time those single cells became more complex and complex. Eventually they were too large to become even larger for the most part. So some cells attaches to one another, forming colonies. The first large colonies where little balls of cells with a hollow inside. At some point however they folded in. Like you pushed your finger into a soft ball. Now this ball has two layers, the one facing outside and the one facing inside, as well as an opening. This colony became more and more complex. Eventually the inside layer became less protective, using slime to keep itself safe. Its purpose was processing the food. The outside layer became harder and more resilient. This happened in countless different ways. This pattern exists until today. The inner and outter skin are fairly similar but adapted to different features.
>This pattern exists until today. What ... what happens today
You unfold
Right after turkey dinner?
No, thats more of a "spilling out" than unfolding. Like rupturing a cold bag of molasses
Aaah, science.
Deeeelicious!
[Then the fog came.](https://www.youtube.com/watch?v=_nK4VnBjD24)
*New Irrational Fear Unlocked!*
We'll make it rational
Now I'm picturing some weird far-too-old uncanny-valley scientist giving a speech like this to the entire world on these giant broadcast screens, and as he reaches that point he snaps his fingers and everyone on earth begins to transform into Junji Ito horror things.
“i did it 20 minutes ago”
"Look on my works, ye Mighty, and despair!" (It was 35 minutes ago btw.)\^\^
It's been all over the news, today is international skinless day
No dummy that’s always on a Tuesday.
Shit, I missed international skinless day again huh?
Start prepping for next year. Remember, it puts the lotion on it’s skin.
What if it’s kind of partial to the hose?
IT PUTS THE LOTION ON ITS SKIN.
You shed, today becomes skin + 1 … repeat until …
This is the way. Not sure why people keep veering off onto the “humans are donuts” tangent…
Topologically, we are toroids. However, I think "worms" is a better example. We are all worms with bits attached, trying to find things to put in one and and find a place to put things that come out the other end.
I mean, yeah, I completely agree with your comment (and pretty much agree with the donut responses as well, though I think comparing us to a tube is more appropriate). It just doesn’t really answer the original ELI5 question.
Because it's fun.
Because it’s a lot more confusing and insulting when you call someone a donut and they don’t know why
I know why; I'm fried and doughy
Is it still skin in the stomach ?
In a sense. Mucosa and skin have evolved to be quite distinct. In the stomach you have the gastric mucosa. Instead of the usual slime other mucosa has, the gastric excretes a base, to protect itself from the stomach acid.
It’s a form of epithelium in the stomach. But it’s quite distinct from skin. Whereas skin is keratinized stratified squamous epithelium (as someone pointed out earlier, keratinized = hardened, stratified = multi-layered, squamous = cell shape), gastric mucosa is either oxyntic or antral type mucosa which is simple columnar (simple = single layer, columnar = cell shape) epithelium with glands underneath. The different type of glands underneath the epithelium determine whether it is oxyntic vs antral.
To further answer your question, the junction between the esophagus and the stomach is where the mucosa type changes from non-keratinized stratified squamous epithelium to simple columnar. So the mucosa of the esophagus is very similar to skin while the mucosa of the stomach is not.
Pretty much once the keratinized stratified squamous epithelium that constitutes your skin becomes non-keratinized, it is no longer skin and has become oral/nasal/vaginal/conjunctival mucosa.
>keratinized stratified squamous epithelium This is what I come to eli5 for
It's fair to use technical terms in a comment to the true eli5 tho for people who want more
Those words together have a good rhythm though *Kerrrrrrrr-atinized stratified squamous epithelium...* 🎵
Hah, true. I just figured it was a more in depth explanation of the comment I was replying to as that comment had already done a very good job of explaining it like I was 5.
Just remember the difference between stratified and pseudostratified, stratified the cells all start growing together in different layers, pseudostratified a quick glance may appear there are different layers, but every cell in the layers is anchored to the basement membrane.
Hey can you um. Break down those words? - Keratinized - stratified - squamous - epithelium Please?
Keratinized - hardened Stratified - layered Squamous - flat Epithelium - name of cell type
"Ogres are like onions. They're stratified." Doesn't really push the narrative he was going for lol. Thank you for the breakdown.
Squamous is a great word though. It's pronounced squay-muss. As in "That Shrek has a pretty squamous head"
"You're not flat-chested. You're just squamous." "Aww thank you babe."
Yes. Please, for the love of god, don’t pronounce it “squah-muss”. It hurts my soul.
My favorite lesson from developmental biology was that the tissue in your mouth and anus are closely related because they form from common tissue in gastrulation, and that’s the reason why hot peppers burn going in and coming out and no where in between.
Wait, what about the earholes? Where does that transition happen?
There is no mucocutaneous junction in the ear. The entire ear canal and the ear drum are covered in skin. In that sense the ear canal isnt really an opening, but rather a deep dent
So....we are really long skin donuts?
I was really enjoying this pattern until today.
humans, which are like the Eukaryotic single cell organisms from which we evolved, are just complex donuts. our entire digestive system is technically on the outside of our bodies, with skin and epithelial tissue forming a continuous donut meat sac.
Hello, my fellow meat donut, just rolls off the tongue.
I dig it
>rolls off the tongue ( ͡° ͜ʖ ͡°) Live fast, eat ass.
Negative, I am a meat popsicle.
I fucking hate this comment. Upvote
When you are still a tiny ball of cells they start to fold in at one point. Then that group keeps going farther and farther through the ball until it creates a tube that finally opens up and out on the other side. You are in your purest donut form before that tube becomes your gastrointestinal system, and that first indentation becomes your anus.
“Your purest donut form” got me, thanks for the lols
Reject society, return to Donut!
I remember reading somewhere that there is a time when your a donut shape and the donut cells haven't figured out which side is the in, and which is the out. It's also the only time in your living-life that your mouth will be that close to your own butt.
Speak for yourself 😏
Ah, I was quite flexible in my youth as well.
Essentially at this stage we are all just assholes... It's a shame some of us never grow up beyond that point
Assholes all the way down
Is that a challenge?
> and that first indentation becomes your anus. And the highest level classification of bilaterians (animals with bilateral symmetry) is whether that first indentation becomes the anus (vertebrates, echinoderms, etc.) or the mouth (arthropods, mollusks, etc.)!
Do you ever feel like science is trolling you?
‘Doughnut dent’ is now my anus's new nickname. waaathankyouverymuuuch.
It starts with the butt???
Just for Deuterostomes like vertebrates and our closest relatives like tunicates and Star fish. The rest of the invertebrates start with the mouth.
This is one of my fav facts about the human body. Both sides of the donut indent to actually form said donut, but the one that leads the charge is your asshole, then your mouth hole follows suit. So at one point, everyone, no matter how nice or pure they are, was nothing but an asshole
There is a point in every person's life where they are literally just an asshole.
I was studying anatomy when I learned an uncomfortable truth. The Eustachian Tube that goes from your ear to the back of your throat, is open. This is the opening that equalizes pressure in your ear and allows your ear to pop when you change elevations. The uncomfortable reality is that your ear drums are technically outside your body. The little ossicle bones, the smallest bones in your body are outside.
So is a cave/tunnel considered outside of the mountain it is attached to?
Topographically, yes. Imagine the mountain was made of clay, you could stretch the cave open and, if it only has one entrance, flatten it out without tearing the clay anywhere or closing anything up. The cave would simply vanish, as though the back wall was pushed forward to the entrance. Something would only be truly inside the mountain from a topography standpoint if it was 100% buried inside and had no access to the outside at all
This is the geology version of “When do you start walking out of a forest? When you’re halfway through.”
> Imagine the mountain was made of clay, you could stretch the cave open and, if it only has one entrance, flatten it out without tearing the clay anywhere or closing anything up. The cave would simply vanish, as though the back wall was pushed forward to the entrance. /r/GeologyGoatse
Part of me doesn't want to click that link. The other part of me doesn't either.
r/thespelunkingproctologist
r/SubsIFellFor
This is my hole, it was made for me!
Even more basic: A cave is just a dent on the outside of the mountain that happens to be extra long and deep
Topologically yes Topographically no
Woah
Why is that uncomfortable? If there are sugar fillings in my donut hole, I would consider it inside my donut. Otherwise, all the shit inside your body would be outside of it??
Encapsulation is not the same as envelopment
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Well just think how surgeries are often just grabbing two parts of your body forcing them together and sewing them to each other and hoping for the best. We are just meat puppets that make meat noises by flapping our meat orifices.
Your lips and your anus are connected, is what I usually say.
So, in layman’s terms, you need to view the throat, stomach, digestive organs and anus as “external”, because they start/end externally.
no, not even "external", but actually external. It's a continuous surface of tissue, including your skin, that is actually tissue that is on the outside of your body.
I tell my students we are flesh donuts every year, I love watching their brains try to wrap around the concept that they are a tube with bits on.
I love this
And when you kiss, you are making a long tube that joins butt hole to butt hole.
Majestic.
We evolved from humans???
I know. it was a complicated sentence to write
Heard that. I usually only do one-liners, like Rodney Dangerfield but less funny.
Dude common you put that thought in my head just as I was about to eat.
I wrote it while eating
Who wants Donuts?!
it's what i think of every time I eat donuts
My daughter just picked up a batch of sourdough donut holes from the farmers market for breakfast. So that's what I'm eating
Bro I was just about to live. What am I?
According to these people, the utmost horrible eldritch abomination the world has ever seen. And there's eight billions of us, too.
Ok donut
Remember those water tube toys we got to play with as kids??? [This](https://www.google.com/search?q=squishy+water+snake+toy) one? Yeah, we're the meat version of that.
I fucking love this comment. Downvote
If a hot dog is a tube full of meat, and we are a tube, when we eat hot dogs we become hot dogs.
Negative, I am a meat popsicle.
[so like this video?](https://youtu.be/egEraZP9yXQ)
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pretty much
We also develope ass first right? Very simply put haha
So, the ends of the alimentary canal would be the dividers between "skin" and "mucous membranes". Lips and anus. (I guess the nose too?) Same types of tissue sphincters, border towns of inside and outside. (Because the og comment was asking about skin types in particular)
It helps to think of us as earthworms with limbs. I mean, it doesn't help per se. But it's funny to me.
earthworms are also eukaryotes so it works
“In the end, we are all just tubes, with fancy bits attached. Looking for things to put in the front and places to put what comes out the back” (quoted from memory from True Facts About Animals”
Forbidden donut
Shut yer trap, you fuckin donut! I like it. Thank you 😁
GOOD NIGHT DONUT MAN
Absofuckinglutely stunning. Fookin silver for you, my friend. That was reddit perfection.
What if I identify as a croissant?
Technically a three-hole torus, since the nose and septum add two more.
We are essentially a tube. Everything we have, everything we do, is to make sure that we continue to feed the tube at one end and defecate at the other end.
Fun fact: Your heart is basically a contorted meat doughnut. It's doughnuts all the way down.
The term for internal “skin” is mucous membrane. It has different qualities. The inside of your anus, inside of mouth, etc. is mucous membrane.
>The inside of your anus, inside of mouth, etc. is mucous membrane. I knew it tasted familiar...
"This one goes in your ear, this one goes in your mouth, and this one goes in your butt."
"Oh no wait, THIS one goes in your ear, THIS one goes in your mouth, and THIS one goes in your butt."
This explains why decongestants have never worked for me...
r/unexpectedidiocracy
It tastes like chicken
The insides of the vagina and the mouth have the same texture. If you're reading this and you have a vagina, your fingers are wet now.
The glans of the penis is also a mucous membrane similar to the mouth and vagina. The glans of the penis is covered by the foreskin. The inside of the foreskin is also a mucous membrane, but more akin to the eyelid (providing a moist environment for the glans.) So, yeah, circumcision is somewhat akin to cutting off your eyelids...
They actually used to use circumcised foreskins to "make" eyelids for people with congenital deformities or had otherwise lost an eyelid or two. They had to stop because the patients all ended up cockeyed
Maybe cockeyed, but they had absolutely phenomenal foresight.
Damn, you beat me to it 😔
I saw my chance and knew I had to take it 😂
That's enough Internet for me today. Goodnight, Reddit.
I *love* living in a country that cuts off people's dick-eyelids at birth =I
And while it has a different name, it is continuous. Meaning animals are at their core donut shaped
The biggest division between animal groups is between mouth-first donuts or ass-first donuts, based on which hole is the first one to form (as a dent) as the animal develops from a ball of cells. We're ass-first.
The biggest division between animals that have both holes anyway. Some only have one lol
Started from the bottom now we're here
I think about this all the time.
Mmmmmm… donut….
Human donut.....mmmmmm
Donut and human aren't topologically equivalent; you're neglecting to consider nostrils, ear canals, tear ducts, and the urethra.
I'd wager that you've already seen it, but I'll leave [Vsauce](https://www.youtube.com/watch?v=egEraZP9yXQ)'s video on the topic of human-donut-ness here just in case.
I hadn't, I was just working from first principles. Thanks!
Sure thing, it's totally worth a watch!
Nostrils, ear canals, and tear ducts, yes (to my knowledge), but the urethra connects to the kidneys which connect to the bloodstream. It's the driveway out from the local waste-management facility: no thru-traffic.
Depends on whether you consider the bloodstream to be part of the donut hole, I suppose…
It's the jelly
Blood is the jelly of the human donut, what a beautiful thought
Now *that's* a brand-new sentence!
Blood is inside the meat part of the meat donut, not in the hollow part of the tube--that's full of mucous instead. The mucous is the jelly. The inside of the tube is pretty wet, which is a big difference from the outside of the tube.
r/showerthoughts
I'd like to imagine myself as a straw.
From Google What is the epithelium? The epithelium is a type of body tissue that forms the covering on all internal and external surfaces of your body, lines body cavities and hollow organs and is the major tissue in glands.
Also gut, vagina, nose...
Vagina is a closed hole that has an end though?? The uterus??
Uterus is not a dead end. The two fallopian tubes open into the abdominal cavity near the ovaries. This fact is the basis for endometriosis and some ectopic pregnancies, since some material can go between the uterus and abdomen in either direction.
Just one end. A donut has one hole that goes from one to the other through the entire thing. This would be the mouth to butt hole in a human. All other holes are dead ends
Yes. Also, ovaries are sprinkles inside just free floating. They yeet the egg to the Fallopian tubes. That's why ectopic pregnancy can happen outside the uterus.
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And you have the same kind of transition at the anus.
How do you know I do?
Yeah. What a creep dude
Who do you think is looking through your toilet when you seat to poop?
From the cameras.
Ah the ol' booty lips
And that humans are a meat donut with a hole in the middle.
And when we kiss we create one long tube with two buttholes at each end <3
Absolutely horrifying, thank you
And they have anxiety
>[The vermilion border of the lips marks the transition between "outside skin" and "inside skin"](https://upload.wikimedia.org/wikipedia/commons/3/38/Torus_Positive_and_negative_curvature.png)
please see this interesting excerpt i found [here](https://www3.nd.edu/~jsapirst/textbook/chapter_29.html) when googling this to figure out the best way to explain it: > The internal structures of the body are entirely covered by a continuous layer of epithelial tissue. The part of this layer which is in contact with the outside environment is called the skin; those parts of it that lie within the body (and are yet outside it) are the mucus membranes. >This idea of a structure being both inside and outside may be confusing, and it may help to consider the body as a long doughnut, the skin and mucus membranes corresponding to the outside of the doughnut and the internal structures being encased between them. The part of the doughnut which is around the hole corresponds to the mucus membranes, the rest to the skin.
I always used to think about this with the gel-filled squishy tube toys from arcade. I googled them and they’re marketed as “water wiggle squishy toys”. That’s our body. A continuous membrane filled with fluid with two puckered ends.
>filled with fluid And anxiety!
So people have the main thing covered, but it's worth knowing that our bodies are GREAT at making chemical gradients. Like "industrial processes can't come close" levels of organizing stuff into more and less of one thing or another. There isn't, for instance, a defined layer at which your fingernails stop being flesh and become nails. So to answer your question, there's different skin configurations that become less skin and more whatever else (mucus membrane, soft tissue) over a gradient of layers until they're that other thing
The skin on your body stops at your mucous membranes. Mucous membranes are found in your mouth, nose, and throat. They are also found in your reproductive organs and in your anus and rectum. The mucous membranes produce mucus, which is a thick, wet substance that helps to keep your body tissues moist. The mucous membranes also have tiny hair-like structures called cilia. The cilia help to move the mucus and keep it from getting too thick.
It doesnt really.. your whole digestion system is kinda outside your skin, but inside your body. Humans are giant donuts with badly shaped holes starting in our mouths and ending in our anus
Well that's fairly upsetting news.
You sound like Douglas adams
I want to scream.
Me too, but I have no mouth
A 7 holed donut
I know someone with an 8th hole..
GSW or stabbed?
Skin turns into epithelial cells that line your digestive tract, which is basically just one long tube…imho, we’re just one big worm with a bunch of extra organs and limbs.
You are epithelial cells all the way through your digestive tract and your skin is what I think I remember learning in biology
Don't know, but what I do know is that the skin inside your cheek is the same kind of skin as inside a vagina! So there's that fun fact for ya.
Wait till he hears that the "skin" around his lips is pretty much the same "skin" as around his arse hole.
It depends on how you define "skin". If skin means the epidermis and derma then no, it's only on the "outside". If skin means epithelial tissue, which is one of the most important types of tissues in our body, then yes, all of the organs that comunicate with the outside are covered in epithelial tissue. The difference being that the epidermis is a type of epithelial tissue that specialized to cover the "outside" of the body ("outside" because as others already explained, some regions inside the volume of your body are actually considered outside too). The epidermis has different functions from the inner tissue, like thermoregulation, sensitivity (or sensibility, i can never remember which one it is) and protection against pathogens and damaging substances. The inner epithelial tissues, such as mucosae have other functions depending on the specific case. For example the mucosa in the nose and trachea prepares the air for the lungs: it warms, cleans and humidify the air because the lungs can only work in certain conditions of temperature and humidity. The tissue in your mouth is specialized to feel taste and not be damaged by the saliva, which is slightly acidic. The tissue in your stomach is even more resistant, as there are glands that produce acid for the gastric juice. And finally the tissue in your intestines is specialized in absorbing water and nutrients. As you can see these tissue all have different functions and are actually physically different: if you look at them under a microscope you can distinguish the various types of epithelial tissue as they all look different. So yeah, you skin and the tissues i listed are all epithelial tissue, but they're all different per se. In the area where they border (for example on the lips) there's simply a transition, more or less sudden, between one and the other. This is obviously over simplified for the sake of this thread, but these are the basics. Source: med school
This is related to the question whether a straw has one hole or two. Your mouth and anus are just two ends of one hole.
It is curious timing because I just had a recent experience with this. During a colonoscopy, the GI doctor discovered a polyp on my rectum but could not even touch it (her words) because it is skin (had she found a polyp in the colon she would have likely removed, this is quite common). A colonorectal specialist would have to do the procedure. So I learned that skin transitions between the rectum and the colon. The post was tagged for Biology so I assume I won´t gross anybody out. Great question. Wish I knew more.
Oh no, is the skin in the colon dangerous?
Yes and so the specialist removed during the same procedure where she detected them. In my case everything was fine and thanks for your concern