You're listening to Brains On, where we're serious about being curious.
Inside you, there is a squelchy, churning pit of liquid.
A liquid so dangerous it would burn your hand if you touched it.
In fact, this super sludge can dissolve all kinds of things, even metal.
Your body makes a lot of it every day.
We're talking about stomach acid.
It's powerful and dangerous.
So why doesn't it burn a hole right through our bodies?
Turns out, our bodies have equally powerful defenses.
We're going to learn all about it.
Plus, imagine if eating rocks was good for you.
For a certain animal, it is.
Find out which animal, coming up.
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You're listening to Brains On.
I'm your host, Molly Bloom, and my co-host today is Wesley from Columbia, Missouri.
Hi, Wesley.
Hi, Molly.
So, Wesley, you inspired this episode with your question about stomach acid.
What was that question?
How does your stomach acid break down your food but not hurt your stomach?
That's such a good question.
I love it so much.
So how did you come up with it?
I was just sitting on the couch after I ate, and it just came into my mind.
Couches are such a good place for ideas.
So what do you think stops it from burning through us?
I think that mucus, like the stuff in your nose, stops it.
Very good idea.
So what foods make your stomach happy, would you say?
Grilled cheese, hot dogs, pizza.
So all the delicious foods.
Is there a food that your stomach does not like?
Most vegetables.
Got it.
Is there any vegetables your stomach's like, yeah, I could do that?
I don't think so.
So if your stomach could talk, what do you think its voice would be like?
I think its voice would be like, hey, I want food.
Give me grilled cheese.
I'm hungry.
Straight to the point.
I'm hungry.
Give me a grilled cheese.
I think mine's like, hello.
I don't know.
Maybe it's more like, hello.
So today we're exploring the wonderful world inside our stomachs.
Yeah, we know our bellies are full of super powerful stomach acid.
Stomach acid is also known as gastric juice.
This soup of stomach stuff is made up of a couple things.
There are digestive enzymes.
These are special chemicals made by your body.
They help break down food.
And then there's hydrochloric acid.
This is a very powerful acid.
Not only does it break down food, but outside of the body, it can burn skin.
Given enough time, it can even dissolve some metals like zinc.
There's also water and some other things in stomach acid.
Every day, your body makes a lot of this stuff, like three to four liters of it.
Picture one of those big party-sized bottles of soda.
Your body could make two of those full of stomach acid every day.
Like we mentioned before, it really makes you wonder.
If this stomach acid is so strong it can dissolve meat, why doesn't it dissolve us?
We're basically meat, too.
To get to the bottom of this belly-busting question, I asked Mark to stop by.
That's right, and I'm here now.
I made the perfect invention to help us get answers.
Ta-da!
It looks like a megaphone with a bunch of coils and blinky lights.
It's the organophone.
It lets you phone any organ.
Huh?
Molly, it's a device that lets you call your body parts.
You just dial them up here on this keypad, and when they pick up, you can ask them questions.
I even made a jingle for it.
You're never alone with the organophone.
You can call the spleen or ring up the heart.
Chat with a lone large or small intestine.
It's the organophone.
I love that jingle so much.
Why, thank you.
Can we talk to the stomach?
Of course.
My stomach is super chatty.
Here, let's give him a call.
Mark, you silly dude.
What is up, my guy?
I mean, besides esophagus, he's always on top of me.
Yo, I swallow food.
Hey, Tom-Tom.
Um, we just wanted to ask you about stomach acid.
You got a sec?
Sure.
I was just doing some stomach crunches, but I can hit pause on that.
Stomach crunches?
You mean sit-ups?
Well, not quite.
Stomach crunches are when I nosh on a bunch of crunchy things.
Oh, yeah.
I had crispy tacos for lunch.
Yeah, you did.
Extra beanie.
Just how I like it.
Me too.
Belly five.
That's when I slap my belly.
Hey, I felt that.
Right back at you, bud.
So, Mark Stomach, tell us how you handle all that stomach acid.
Of course, Molinator.
Check it out.
So when Mark is eating, he starts by chewing up his food.
Nom, nom, nom, nom.
That makes it all mushy and wet.
Then it's swallowed by the esophagus.
Yo, I'm a muscular tube.
Yeah, you are, bro.
When the food gets to me, that's when stomach acid starts doing its thing.
So the stomach, or you, start making the acid when the food is swallowed?
Actually, stomach acid is made even before you eat.
We need to be ready down here.
Sometimes just thinking about eating, like looking at a delicious plate of fiber-filled bean tacos will get my juices flowing.
Yeah, that way the digestion party can start the second most tasty tacos touchdown in Bellytown.
The acid in me is strong.
It helps dissolve the food into a slush.
It can even kill a lot of nasty germs.
There are also enzymes in the mix that can help break down proteins in things like meats and beans.
Stomach.
I think you're being a little modest.
You also help break down food by churning it up and squeezing it, right?
Well, you know I don't like to brag, but that is my digestive dance.
Squeeze and churn.
Squeeze and churn.
Sounds like a lot of action, but how come you aren't hurt by all that acid?
Oh, Molly, I have my ways.
And by ways, I mean mucus.
Mucus?
I knew it was going to be that.
Yep.
Or as I like to call it, liquid gold.
100% agree.
Mucus is the absolute queen.
In your nose, it helps keep the air you breathe warm and moist.
It traps germs and dust and other allergy-causing things.
It's nature's glue trap.
I'm team mucus all the way.
Me too.
Down here in my world, mucus is very important stuff.
There are these glands in me that make a lot of mucus.
And that mucus acts like a shield protecting my walls from all that nasty acid.
Plus, the mucus is full of stuff called bicarbonate.
Bicarbonate?
That sounds familiar.
Wait, isn't that baking soda?
The stuff I bake with?
Good catch, Wesley.
That's right.
Baking soda is sodium bicarbonate.
And bicarbonate is the bicarbo-bomb.
When it comes to stopping acid, I mean.
You see, bicarbonate is super alkaline.
That means it's the opposite of acid.
Correct.
And when you mix acids and alkaline stuff together, they sort of cancel each other out.
So the mucus has bicarbonate that helps neutralize the acid?
Exactly.
The bicarbonate helps stop the acid from being so, I don't know, acidy.
Plus, my other main defense is to just shed a lot of cells.
Cells.
Those are the little pieces we are made of.
Our body is made up of tons and tons of cells.
Hair cells.
Eye cells.
Brain cells.
And stomach cells?
Mine sort of sacrifice themselves constantly.
They fall off the walls of me, the stomach.
And that helps protect the deeper parts of my walls from getting acid blasted.
And those cells grow back pretty quick, too.
Like an armor that regenerates.
In fact, the entire lining of the stomach is replaced every couple days.
Wow, so the acid in the stomach is serious stuff, but the stomach has mucus to help protect it.
And the mucus has stuff in it that helps neutralize the acid.
Also, the lining of the stomach is constantly shedding and regrowing due to the acid.
Thanks for stopping by with your new invention, Mark.
And thanks for all that info, Mark's stomach.
No problem.
And thanks for all you do, stomach.
Hey, I'll keep digesting if you keep feeding me extra beanie hot and cheesy tacos.
Oh, it's my bum bum calling.
I wonder what's up.
Hey, Mark.
Stomach.
About those extra beanie tacos.
Can you actually give it a rest?
I gotta fart all that stuff out eventually, and it's exhausting.
I need a break.
Wow, sorry, dude.
I didn't... Just kidding.
I love tooting.
Keep those beans coming.
In fact, I want more.
Me too.
Well, that makes three of us.
Yo, I like swallowing them.
All of me loves beans.
Beans, frijoles, black and pinto.
We love them at the table.
We love them on the go.
Beans, frijoles, pinto and black.
Like a song in the mouth and music in the back.
Wow, that was a very helpful stomach.
Totally.
I really learned a lot.
I hope your ears are ready to be helpful because it's time for the... Mystery Sound.
Are you ready for the Mystery Sound, Wesley?
Yep.
All right.
Here it is.
Hmm.
What is your guess?
It sounds like someone has a fork and they're banging the fork against a pan.
Totally.
That's like literally exactly what I was picturing.
Let's hear it one more time.
Okay.
Any new thoughts?
I still think it's that, and they dropped the fork at the end.
Yeah, they're like, mic drop, that was a great drumming session I had, and they dropped it.
Okay, I'm into it.
We're going to hear it again, get another chance to guess and hear the answer at the end of the show.
Stay with us.
Hi, friends.
Do you have a question you'd like to hear answered on the show?
No question is too big or too small.
Did you hear something in your like...
Is that really true?
Were you hanging out and a question just like popped into your head?
Do you have a thought experiment you'd like us to explore?
Like if there was a lake of lemonade, would it rain lemonade?
That's a real question that we got and we answered it.
So head to brainson.org slash contact and send us your question.
Thank you.
We'll be right back.
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You're listening to Brains On.
I'm Molly.
And I'm Wesley.
And we've learned that our stomachs are full of dangerous, burny, melty acid.
Lucky for us, they are also full of mucus.
That protects our stomach, and they can regrow their lining super fast when the acid damages it.
It's a very cool system, but there are lots of other neat ways to digest food, as you're about to find out.
Cue the lights.
Prep the questions.
And gimme my blazer because it's time for a game show.
This game is called Digestion Suggestion.
Here's how it works.
I'm going to give you a suggestion for a cool way to digest food.
And you have to guess what animal uses that mode of digestion.
Are you ready?
Yep.
All right, let's go.
Some people think this animal has four stomachs, but that's a myth.
It has one stomach with four parts.
It likes to eat its food quickly, then go take a break and voluntarily unswallow its food so it can chew it some more.
Whose digestion suggestion is this?
Is it A, a cow, B, a seal, C, a lion, or D, a dog?
I'm going to go with A, a cow.
You are correct.
Very good.
Yes, so when an animal is chewing its food, after it burps it back up, that's called chewing cud.
All right, next question.
This animal eats rocks on purpose.
These little pebbles are called stomach rocks and the animal holds them in a muscular part of the stomach called the gizzard.
They use these rocks to help grind down the food they swallow.
Whose digestion suggestion is this?
A, an ostrich.
B, a giraffe.
C, a Gila monster.
Or D, a snake.
I'm going to go with a Gila monster.
Oh, excellent guess.
But it is an ostrich.
Other birds have these gizzards too.
So over time, the rocks wear out and the ostrich eats more rocks.
Yummy, yummy.
All right, next question.
Eggs are tasty when cracked and fried, but this animal eats them shell and all.
It opens wide and swallows the whole egg.
Then it uses muscles to push the egg against sharp spines inside of it.
That cracks the shell so the runny, eggy goo can ooze out.
The animal swallows the goo and then throws back up the shell.
Whose digestion suggestion is it?
Is it A, egg-eating rhino, B, egg-eating turtle, C, egg-eating badger, or D, egg-eating snake?
I'm going to go with an egg-eating badger.
Excellent, excellent guess, but the answer is a snake.
Surprisingly, they actually throw up the shells pretty much fully intact, which is incredible, and I have no idea how that works.
All right, next question.
Everything about this animal is kind of ew to us, but yum to them.
For starters, they like to eat stuff that's been dead for a while.
It doesn't really chew its food.
It swallows it in chunks, and it stuffs itself with as much rotting carcass as it can.
It even has a little pouch in its throat where it can store the gross meat for future meals.
Whose digestion suggestion is this?
A. Wolves.
B. Vultures.
C. Vampire frogs.
Or D. Hamsters.
I'm going to go with a vulture.
And you are correct.
Vultures have extra super strong stomach acid which pretty much kills all the germs in the rotting animal they eat.
That's how come they don't get sick from eating it.
Excellent, excellent work, Wesley.
Thank you for playing Digestion Suggestion.
You did great.
And your prize is not having to eat like any of these animals.
Enjoy not eating rocks, not throwing up eggshells, not rechewing your food and not eating rotting flesh.
Congratulations.
That game made me the opposite of hungry, but it sure was fun.
Anything in there that really surprised you?
I'm surprised that the cow re-eats its food.
Yeah, that's pretty gross.
But, you know, they got to do it.
They got to get all those nutrients out.
So if you could have the power to digest anything in the world like something that we can't eat, what would you want to eat and why?
I'm trying to think of something with a lot of protein.
I like that.
I'm going to say, if I got to eat a microphone and spit it back out like the cow, would I just get a really loud voice for a long time?
Oh, I really like that.
Excellent answer.
I'm Wesley.
Can you hear me now?
Now let's hit pause on digestion for a minute and see what's new in the mailroom.
It's time for the mailbag.
Heyo, Sandon with the mailbag.
I'm checking your letters and emails from my new favorite room in our headquarters.
It's the Bovinal Lounge.
I hang out with bovines, aka cows, and I lounge about listening to my vinyl records, like this one.
Let's hear some of your ideas for new rooms to add to our headquarters.
You should add a coffee mug farm to your new headquarters.
You will be able to drink hot cocoa anytime you would like, and you don't have to wash your mug because you grow them.
Hi, I think you should have a manatee room that you can play with manatees.
And there's also stuff that manatees need, like mango leaves, shallow water, and seed grain.
Hi, I have two ideas for your new HQ.
I think that you should have a donut room, which has a half donut on the door.
And in the inside, there's going to be lots of donut furniture.
For my second idea, I think you should have a party room which has all the party supplies you could imagine.
And also, I think that Sandman's really funny.
Whoa, I also think I'm very funny.
And so does Milfred.
She's my couch.
That's a cow that I also curl up on like a couch.
Here in the Bovina Lounge, all of the furniture is bovine furniture.
Mmm, so cozy to cuddle a cow.
Okay, well, thanks to Warren, Blake, and Francis for these ideas.
We'll get right on them.
And by we, I mean Molly and Mark.
Because I've got more records to listen to.
Cheers!
Brains On is fully independent.
That means me, Mark, and Shannon can only keep doing this when people support the shows.
The best way is by joining Smarty Pass.
When you do, you get access to ad-free versions of all of our episodes and Smash Boom, Best and Forever Go Too.
Help out by going to smartypass.org.
Thank you.
Welcome back.
I'm Molly here with Wesley.
Today, we've learned that our bodies make powerful acid in our stomachs to help break down food.
Right.
But our stomachs protect themselves by making a ton of magical mucus.
And by shutting a lot of stomach lining cells and growing new ones.
So how did humans figure out what's going on in the stomach anyway?
It's not like we can peek in there.
And no one has an organophone except Mark.
Turns out, some of the first things we learned about how the stomach works came after a serious accident.
It was back in 1822, the time of horse-drawn carriages.
No electricity.
Handwritten letters.
No cars.
They had gas lamps.
And some questionable ways of treating patients.
As we're about to learn, our story starts with a man named Alexis St.
Martin.
One day, he was shopping at a general store when he was accidentally shot.
Luckily, there was a doctor nearby who could help.
His name was William Beaumont.
He saved Alexis's life and allowed him to live with him as he got better.
Here's where things go weird.
Alexis got better, but his wound didn't heal like you would expect.
Instead of the skin growing over the hole, it stayed open.
That's called a fistula.
So basically, there was an opening and you could see Alexis' stomach working.
William, the doctor, thought this was super interesting.
He started doing experiments with Alexis' stomach.
He would tie food to a string and put it in the stomach.
Part of the string was left dangling outside the opening.
Then he could pull the string to take the food out.
He'd see how it changed and then he would put it back inside.
He would do this over and over.
It was often uncomfortable or even painful for Alexis.
But William learned a lot.
He wrote a whole book.
And it changed how we understand digestion.
Today, people think what William did was questionable.
Here's why.
For starters, it's not clear why he didn't try to close the wound.
It certainly would have been better for Alexis if it was closed.
Was it impossible to fix, or did William leave it open so he could do his experiments?
Also, Alexis ended up working for William.
He signed contracts saying he would help with chores and stuff.
Alexis got money and food and a room to sleep in, but also the contracts said William would get to experiment on him.
People aren't sure if Alexis really wanted to be experimented on or if he just felt like he had to sign those contracts so he could survive.
Today, scientists who want to do an experiment are supposed to explain it to a group of other scientists.
And those other scientists make sure that the experiments are ethical, which means it is safe, fair and no one is treated badly.
Back then, we didn't have many ways to find out what was going on in the body.
But today, we have scanners and cameras that can safely take pictures of our insides.
Fancy technology for our fantastic bodies.
Our stomachs are full of powerful acids that help break down food.
Those acids can also burn skin and even melt metal.
Luckily, our stomachs make a lot of mucus that helps protect it from the acid.
And the stomach lining is replaced every couple of days, so damaged parts are fixed pretty quickly.
That's it for this episode of Brains On.
Special thanks to Jeff Martin Carrie Martin, Mark Johnson, Ked Taborski and Code of the North for their help with our website.
I think it's time to go back to that mystery sound again.
Should we hear it?
Let's do it.
All right.
Here it is.
Do you have any new thoughts?
I'm going to stick with my original answer.
So you thought it was someone banging on a pan, a metal pan with a fork, and then dropping it at the end, sort of like yeah, I did that.
Yeah.
Yeah, I think it's a great answer.
Should we find out if you were right?
I want to see.
All right, here it is.
My name is Owen Smith, and that was the sound of me flicking the tab on a soda can until it popped off.
Excuse me?
Flicking a tab on a soda can.
That's amazing.
Also, so loud.
Very hard to guess.
So hard to guess.
So you were correct.
There was metal going on.
I guess when things are mic'd up close they sound so much louder than they do like when you're far away.
Oh, so tricky.
I'm giving you partial credit, though, because you knew metal was happening.
So, partial credit for you, no credit for me, because I didn't even have a good guess.
Well done.
Way to trick us.
Now it's time for the Brain's Honor Roll.
These are the incredible kids who keep the show going with their questions ideas, mystery sounds, drawings and Thank you.
Avi from Oak Harbor, Washington.
Dominic from Richmond, California.
Samantha from Sammamish, Washington.
Anjali from Columbia, Maryland.
Dia and Connor from Pennsylvania.
Miles from Chappaqua, New York.
Lena and Daphne from Southampton, Ontario.
Lily from Clarksville, Maryland.
Benjamin and Matthew from Okinawa, Japan.
Calder and Evie from Philadelphia.
Liam from Galex, Virginia.
Tessa from Oregon City.
Jesse from Philadelphia.
Anna from San Jose, California.
Braxton from Richmond, Texas.
Jesse and Aria from Panama City, Florida.
William from Washington, D.C.
Jade from Holtz Summit, Missouri.
Kaylin from Oklahoma.
June of Purr from Sacramento.
Kai from Fountain Valley, California.
Calvin, Jasper, Lily, and Florence from Orem, Utah.
Thank you.
Elizabeth from Chicago, Olivia from Main Island, Canada, Nona from Portland, Oregon, Mira and Soren from Charlotte, North Carolina, Edith from Anchorage, Alaska, Mae from Tacoma, Washington, Will from Savannah, Georgia, Emma from Holliston, Massachusetts, Jonathan from Golden Valley, Minnesota, and Izzy from Tampa, Florida.
We'll be back next week with an episode all about different generations.
Thanks for listening.
