7 ms·

I'm just as fascinated by the valve at the base of the stomach, called the pyloric sphincteric cylinder. It uses an ingenious mechanism to selectively pass liq

I'm just as fascinated by the valve at the base of the stomach, called the pyloric sphincteric cylinder. It uses an ingenious mechanism to selectively pass liquid and very small particles to the small intestine, while keeping larger chunks in the stomach for further digestion. It functions like a screen or filter, but with a simple, robust, and reliable structure. Here's a fantastic (and free) book about just this structure: http://med.plig.org/ http://med.plig.org/

bbkane 5y ago
This book is not super friendly to a newcomer to the sphinctor. I was unable to finish the Introduction due to the unexplained technical jargon immediately presented.
- nate_meurer 5y ago
  It does assume some background knowledge on the part of the reader, but that's a necessary feature of any advanced technical book or treatise. I'm not an expert in, well, anything, so I rely a lot on Wikipedia for the basics.
  - FridayoLeary 5y ago
    A kindred spirit! You and i must be among a select group of individuals.
kccqzy 5y ago
To me the most fascinating aspect is not filtering out large chunks, but that it prevents the highly acidic gastric fluid (the pH ranges from 1 to 3) in the stomach from reaching and damaging the small intestine. The stomach is equipped to deal with the extremely acidic fluid for digestion, but the small intestine is not.
- nate_meurer 5y ago
  Neutralization of acid is actually done in the duodenum. We have organs called Brunner's glands lining the top half of the duodenum that secret a special mix of alkaline bicarbonates and growth factors in a thick mucin carrier. This neutralizes the gastric acids and lines the small intestines with protective mucus. You're right though, the engineering that goes into our bodily machines is mind boggling.
  - BuyMyBitcoins 5y ago
    I’m in awe at how much time and countless generations it took to evolve these mechanisms.
    - RedComet 5y ago
      lmao
    - brabel 5y ago
      Nature has an unimaginable amount of time at its disposal, and no morals at all holding back its "experimentation".
  - rawoke083600 5y ago
    Man.. I wish there were more research and therapies in this regard... I've been on PPI for over 20 years because of consistent heartburn... (Sliding hernia). The operation to "fix" it they wrapped your stomach around your oesophagus but that seems like not a great solution..
    - redok 5y ago
      You will soon have other options: https://www.implantica.com/im-refluxstop/patients/gastrointestinal/ https://www.implantica.com/im-refluxstop/patients/gastrointe...
    - sneak 5y ago
      Anecdotes are not data but I was able to stop a long history of upper GI issues (and terrible heartburn and acid reflux) by drastically changing my diet. Turns out I'm not compatible with the standard western food staples.
barbarr 5y ago
>It uses an ingenious mechanism to selectively pass liquid and very small particles to the small intestine, while keeping larger chunks in the stomach for further digestion Do you have an ELI5 for how this works?
- nate_meurer 5y ago
  Sure, hold out your hands in front of you like you're holding a hose with both hands vertically, one fist on top of the other. Imagine the tube is hanging from a bag full of liquid (a stomach). Now squeeze your bottom fist, and relax your top fist, and imagine the liquid filling the top part of the hose. Now relax your bottom fist a bit and squeeze your top fist, and image liquid squirting out both ends of the top part of the hose-- both forward into the bottom part and upward back toward the stomach. That's a good model of your pylorus, except the bottom fist is more like a ring, and the tube isn't vertical but horizontal, and in fact, the bottom of your stomach curves around such that the pylorus is actually squirting liquid (called chyme) upward into your small intestine. But the vertical fists model helps to visualize the pylorus as a "cylinder" of annular muscle segments that contract and relax with alternating timing to pump liquid from the stomach into the duodenum in precise metered doses. This timed and coordinated squeezing action is called peristalsis, and is the mode of action of all your intestines as well as your esophagus. Now here's the important part: notice that when you squeezed your top fist, liquid squirted out in both directions. Dynamic studies of the pylorus in action show that these two "squirts" are not the same. The forward squirt is usually smaller and contains only liquid and fine particles of food, whereas the larger backward squirt (called retropulsion) contains all of the large chunks of food that require further digestion. So how does the pylorus do this? The answer lies largely in the shape and structure of the sphincter wall, and here's where it gets really crazy. The pyloric cylinder has two sets of muscles moving it: the big strong external rings of muscle, and a finer inner layer of muscle in the mucosal lining. When these muscles contract and relax, the inner mucosal lining forms various patterns of folds and wrinkles. When the pylorus is pumping liquid from the stomach to the small intestine, the two sets of muscles work together to shape folds and wrinkles that "grip" chunks of food, prevent them from passing, and then launch them backward, back into the stomach. The shapes of the folds is highly variable, and it appears that your pylorus adapts these intricate patterns in its lining from moment to moment based on the properties of the food in your stomach-- it's texture, viscosity, the shapes and sizes of the chunks in it, etc. How does your stomach "know" these details about the food in it? I don't think anybody really knows yet. In case anyone's looking for an exact source, here's the money quote from page 62 of the book: > A certain contraction of the outer muscular tube is necessary for the formation of macroscopic mucosal folds. The variability of the fold pattern is also dependent on the hydrodynamic action of the fluid content of the submucosa, which in turn depends on the degree of filling of the blood vessels; the mass of mucous membrane, and consequently the volume of its folds, is regulated by the varying vascularity in the submucosa. > In addition Forssell showed that the surface of the mucosa, or mucosal relief pattern, may vary from moment to moment; these movements are independent of, but co-ordinated with the contractions of the muscularis externa. Especially in the small intestine, but also in the stomach, various active contractile shapes, in some of which the mucosa "grips" particles of food, may be discerned. These consist of digestion chambers, blocking or filtering devices, re-absorption reservoirs and smooth or corrugated transporting tubes. In this way each region may best meet the varying demands placed on it from moment to moment, namely digestion, storage, absorption and transport respectively. One moment the mucosa may be occupied with one task, the next with another. Forsell called the inherent ability of the mucosa to move "mucosal autoplastik", providing a working relief pattern. It also determined to a large extent the number, position and form of the folds. While the coarser breakdown of food particles is effected by contractions of the muscularis externa, the finer dispersion occurs through changes in the relief pattern of the mucosa, which may enhance or counteract effects of contraction of the muscular walls. The special contractile organ of the mucous membrane is the muscularis mucosae; being attached to the mucosa and being incorporated in the submucosa, it is able to displace the former in different directions. --- EDIT It's been almost twenty years since I read this book, and re-reading the quote above, I realize that this wild mechanism I described is also used in the small intestine (not just in the distal stomach and pylorus). It makes perfect sense, but it never occurred to me that this is how a whole lot of our guts work to move and process food. It's kind of another epiphany for me.
gadders 5y ago
I can't hear talk of Pyloric Valves now without thinking of Confederacy of Dunces: https://en.wikipedia.org/wiki/A_Confederacy_of_Dunces https://en.wikipedia.org/wiki/A_Confederacy_of_Dunces (Great book btw)
therealasdf 5y ago
I'm convinced that who ever came up with this valve was inspired by anuses. Its a clever way to dispense honey without making a mess. Anus inspired honey dispenser https://imgur.com/a/jmQUSYr https://imgur.com/a/jmQUSYr
- CapmCrackaWaka 5y ago
  Is this safe for work? Because I'm interested, but currently on a work computer.
  - yoshyosh 5y ago
    Yes it's just the tops of honey bottles
  - ChoGGi 5y ago
    It looks like a squeezable honey bottle that can prolapse (not what I expected to write on HN today).
    - sangnoir 5y ago
      ...that's not what a prolapse is. A prolapse is when the internal bits get distended, or otherwise protrude through the orifice when it's supposed to be "closed". That hone bottle is working as designed.
- albrewer 5y ago
  What is this kind of valve called?
mrfusion 5y ago
So does it eventually give up and allow bigger objects through? You’d think it would need a mechanism to handle undigestible items (as any dog owner knows)
- EForEndeavour 5y ago
  In my dog-owning experience, the mechanism to handle undigestible items is to vomit them back out.
  - dahfizz 5y ago
    My uncle had a dog who loved nothing more than to eat socks, and poop them out.
  - thejackgoode 5y ago
    It's funny with dogs, how nuts come out from the other side as they came in, untouched by a single enzyme
- nate_meurer 5y ago
  It definitely does, and it's normal operation. We're supposed to eat lots of indigestible material; whole vegetables and grains contain a lot of indigestible fiber, which is necessary to support a healthy gut biome and efficient bowel operation. Corn husks, for example, are easy to see when they come out the other end. So here again, how does your stomach "know" when to stop trying to digest certain pieces of food and let them pass on to the small intestine? This topic is called gastric emptying, and it's a whole other rabbit trail. Your stomach monitors the chemistry of the food in it-- specifically, the chemistry of the digestion products generated as the food breaks down. It knows lots of details about the carbohydrate, protein, and fat being released, and it knows how quickly its digestive enzymes and acids are being used up. So it knows how much more work needs to be done, and whether or not its worth trying to get more nutrients out of a piece of unchewed nut, for example. There are many other variables, and I think digestion is still largely shrouded in mystery. Studies have shown variation in gastric emptying rates based on the biological activity of food, infections in gut tissues (even if they're subclinical, i.e., you don't feel unwell), time of day, and even the person's emotional state. The guts are the seat of a large part of the autonomous nervous system, and science has barely scratched the surface of it.
drdeadringer 5y ago
> the pyloric sphincteric Fun fact: I had pyloric stenosis as an infant. IIRC, this condition tends to hit first born males of which I am one. Dearest mother kept bringing me into the hospital. "He keeps throwing up no matter what." She kept being told the "oh you're just a new mother" song until finally one doctor switched on a lightbulb to check something out. Next thing is that I'm this infant on an adult stretcher being prep'd for surgery. My oldest scar. I swear if I was born 100 years earlier I'd be dead by starvation at no fault of anything but medical innovation.
- felipellrocha 5y ago
  Dude. I almost wrote thr same comment yesterday. I love science today because of this. Also my oldest scar.
- djhn 5y ago
  Wouldn't dehydration hit before starvation? In any case, congratulations on your continued survival!
- sopooneo 5y ago
  When you say “switched on a lightbulb” is that figurative? Or did bright light somehow make your condition apparent? Sorry if I’m being daft here.
  - drdeadringer 5y ago
    Figurative. As in "fine, let's just check this out because you keep coming back and why not?" which turned into "well heck, it is this condition -- page Dr Smith, we need paediatrics in surgery".

bbkane 5y ago

This book is not super friendly to a newcomer to the sphinctor. I was unable to finish the Introduction due to the unexplained technical jargon immediately presented.

nate_meurer 5y ago
It does assume some background knowledge on the part of the reader, but that's a necessary feature of any advanced technical book or treatise. I'm not an expert in, well, anything, so I rely a lot on Wikipedia for the basics.
- FridayoLeary 5y ago
  A kindred spirit! You and i must be among a select group of individuals.

kccqzy 5y ago

To me the most fascinating aspect is not filtering out large chunks, but that it prevents the highly acidic gastric fluid (the pH ranges from 1 to 3) in the stomach from reaching and damaging the small intestine. The stomach is equipped to deal with the extremely acidic fluid for digestion, but the small intestine is not.

nate_meurer 5y ago
Neutralization of acid is actually done in the duodenum. We have organs called Brunner's glands lining the top half of the duodenum that secret a special mix of alkaline bicarbonates and growth factors in a thick mucin carrier. This neutralizes the gastric acids and lines the small intestines with protective mucus. You're right though, the engineering that goes into our bodily machines is mind boggling.
- BuyMyBitcoins 5y ago
  I’m in awe at how much time and countless generations it took to evolve these mechanisms.
  - RedComet 5y ago
    lmao
  - brabel 5y ago
    Nature has an unimaginable amount of time at its disposal, and no morals at all holding back its "experimentation".
- rawoke083600 5y ago
  Man.. I wish there were more research and therapies in this regard... I've been on PPI for over 20 years because of consistent heartburn... (Sliding hernia). The operation to "fix" it they wrapped your stomach around your oesophagus but that seems like not a great solution..
  - redok 5y ago
    You will soon have other options: https://www.implantica.com/im-refluxstop/patients/gastrointestinal/ https://www.implantica.com/im-refluxstop/patients/gastrointe...
  - sneak 5y ago
    Anecdotes are not data but I was able to stop a long history of upper GI issues (and terrible heartburn and acid reflux) by drastically changing my diet. Turns out I'm not compatible with the standard western food staples.

barbarr 5y ago

>It uses an ingenious mechanism to selectively pass liquid and very small particles to the small intestine, while keeping larger chunks in the stomach for further digestion Do you have an ELI5 for how this works?

nate_meurer 5y ago
Sure, hold out your hands in front of you like you're holding a hose with both hands vertically, one fist on top of the other. Imagine the tube is hanging from a bag full of liquid (a stomach). Now squeeze your bottom fist, and relax your top fist, and imagine the liquid filling the top part of the hose. Now relax your bottom fist a bit and squeeze your top fist, and image liquid squirting out both ends of the top part of the hose-- both forward into the bottom part and upward back toward the stomach. That's a good model of your pylorus, except the bottom fist is more like a ring, and the tube isn't vertical but horizontal, and in fact, the bottom of your stomach curves around such that the pylorus is actually squirting liquid (called chyme) upward into your small intestine. But the vertical fists model helps to visualize the pylorus as a "cylinder" of annular muscle segments that contract and relax with alternating timing to pump liquid from the stomach into the duodenum in precise metered doses. This timed and coordinated squeezing action is called peristalsis, and is the mode of action of all your intestines as well as your esophagus. Now here's the important part: notice that when you squeezed your top fist, liquid squirted out in both directions. Dynamic studies of the pylorus in action show that these two "squirts" are not the same. The forward squirt is usually smaller and contains only liquid and fine particles of food, whereas the larger backward squirt (called retropulsion) contains all of the large chunks of food that require further digestion. So how does the pylorus do this? The answer lies largely in the shape and structure of the sphincter wall, and here's where it gets really crazy. The pyloric cylinder has two sets of muscles moving it: the big strong external rings of muscle, and a finer inner layer of muscle in the mucosal lining. When these muscles contract and relax, the inner mucosal lining forms various patterns of folds and wrinkles. When the pylorus is pumping liquid from the stomach to the small intestine, the two sets of muscles work together to shape folds and wrinkles that "grip" chunks of food, prevent them from passing, and then launch them backward, back into the stomach. The shapes of the folds is highly variable, and it appears that your pylorus adapts these intricate patterns in its lining from moment to moment based on the properties of the food in your stomach-- it's texture, viscosity, the shapes and sizes of the chunks in it, etc. How does your stomach "know" these details about the food in it? I don't think anybody really knows yet. In case anyone's looking for an exact source, here's the money quote from page 62 of the book: > A certain contraction of the outer muscular tube is necessary for the formation of macroscopic mucosal folds. The variability of the fold pattern is also dependent on the hydrodynamic action of the fluid content of the submucosa, which in turn depends on the degree of filling of the blood vessels; the mass of mucous membrane, and consequently the volume of its folds, is regulated by the varying vascularity in the submucosa. > In addition Forssell showed that the surface of the mucosa, or mucosal relief pattern, may vary from moment to moment; these movements are independent of, but co-ordinated with the contractions of the muscularis externa. Especially in the small intestine, but also in the stomach, various active contractile shapes, in some of which the mucosa "grips" particles of food, may be discerned. These consist of digestion chambers, blocking or filtering devices, re-absorption reservoirs and smooth or corrugated transporting tubes. In this way each region may best meet the varying demands placed on it from moment to moment, namely digestion, storage, absorption and transport respectively. One moment the mucosa may be occupied with one task, the next with another. Forsell called the inherent ability of the mucosa to move "mucosal autoplastik", providing a working relief pattern. It also determined to a large extent the number, position and form of the folds. While the coarser breakdown of food particles is effected by contractions of the muscularis externa, the finer dispersion occurs through changes in the relief pattern of the mucosa, which may enhance or counteract effects of contraction of the muscular walls. The special contractile organ of the mucous membrane is the muscularis mucosae; being attached to the mucosa and being incorporated in the submucosa, it is able to displace the former in different directions. --- EDIT It's been almost twenty years since I read this book, and re-reading the quote above, I realize that this wild mechanism I described is also used in the small intestine (not just in the distal stomach and pylorus). It makes perfect sense, but it never occurred to me that this is how a whole lot of our guts work to move and process food. It's kind of another epiphany for me.

gadders 5y ago

I can't hear talk of Pyloric Valves now without thinking of Confederacy of Dunces: https://en.wikipedia.org/wiki/A_Confederacy_of_Dunces https://en.wikipedia.org/wiki/A_Confederacy_of_Dunces (Great book btw)

therealasdf 5y ago

I'm convinced that who ever came up with this valve was inspired by anuses. Its a clever way to dispense honey without making a mess. Anus inspired honey dispenser https://imgur.com/a/jmQUSYr https://imgur.com/a/jmQUSYr

CapmCrackaWaka 5y ago
Is this safe for work? Because I'm interested, but currently on a work computer.
- yoshyosh 5y ago
  Yes it's just the tops of honey bottles
- ChoGGi 5y ago
  It looks like a squeezable honey bottle that can prolapse (not what I expected to write on HN today).
  - sangnoir 5y ago
    ...that's not what a prolapse is. A prolapse is when the internal bits get distended, or otherwise protrude through the orifice when it's supposed to be "closed". That hone bottle is working as designed.
albrewer 5y ago
What is this kind of valve called?

mrfusion 5y ago

So does it eventually give up and allow bigger objects through? You’d think it would need a mechanism to handle undigestible items (as any dog owner knows)

EForEndeavour 5y ago
In my dog-owning experience, the mechanism to handle undigestible items is to vomit them back out.
- dahfizz 5y ago
  My uncle had a dog who loved nothing more than to eat socks, and poop them out.
- thejackgoode 5y ago
  It's funny with dogs, how nuts come out from the other side as they came in, untouched by a single enzyme
nate_meurer 5y ago
It definitely does, and it's normal operation. We're supposed to eat lots of indigestible material; whole vegetables and grains contain a lot of indigestible fiber, which is necessary to support a healthy gut biome and efficient bowel operation. Corn husks, for example, are easy to see when they come out the other end. So here again, how does your stomach "know" when to stop trying to digest certain pieces of food and let them pass on to the small intestine? This topic is called gastric emptying, and it's a whole other rabbit trail. Your stomach monitors the chemistry of the food in it-- specifically, the chemistry of the digestion products generated as the food breaks down. It knows lots of details about the carbohydrate, protein, and fat being released, and it knows how quickly its digestive enzymes and acids are being used up. So it knows how much more work needs to be done, and whether or not its worth trying to get more nutrients out of a piece of unchewed nut, for example. There are many other variables, and I think digestion is still largely shrouded in mystery. Studies have shown variation in gastric emptying rates based on the biological activity of food, infections in gut tissues (even if they're subclinical, i.e., you don't feel unwell), time of day, and even the person's emotional state. The guts are the seat of a large part of the autonomous nervous system, and science has barely scratched the surface of it.

drdeadringer 5y ago

> the pyloric sphincteric Fun fact: I had pyloric stenosis as an infant. IIRC, this condition tends to hit first born males of which I am one. Dearest mother kept bringing me into the hospital. "He keeps throwing up no matter what." She kept being told the "oh you're just a new mother" song until finally one doctor switched on a lightbulb to check something out. Next thing is that I'm this infant on an adult stretcher being prep'd for surgery. My oldest scar. I swear if I was born 100 years earlier I'd be dead by starvation at no fault of anything but medical innovation.

felipellrocha 5y ago
Dude. I almost wrote thr same comment yesterday. I love science today because of this. Also my oldest scar.
djhn 5y ago
Wouldn't dehydration hit before starvation? In any case, congratulations on your continued survival!
sopooneo 5y ago
When you say “switched on a lightbulb” is that figurative? Or did bright light somehow make your condition apparent? Sorry if I’m being daft here.
- drdeadringer 5y ago
  Figurative. As in "fine, let's just check this out because you keep coming back and why not?" which turned into "well heck, it is this condition -- page Dr Smith, we need paediatrics in surgery".