Science Friday - Big Trees, Masks And Singing, Capturing Holiday Scents, Unseen Body. Dec 17, 2021, Part 2

Episode Date: December 17, 2021

Big Trees, Big Benefits When you think about big trees, likely what comes to mind are some of the Earth’s biggest trees, like giant sequoias or redwoods, which can grow to roughly 25 stories tall. But big trees are actually an essential part of every forest ecosystem. Big trees capture a disproportionate share of carbon, provide important animal habitats, propel new tree growth and provide much needed shade. The largest one percent of trees or those which measure roughly 2 feet or larger in diameter are considered the big trees of any forest. Jim Lutz, an associate professor of forest ecology at Utah State University in Logan, Utah joins guest host John Dankosky to explore the wonderful world of big trees. Lutz is also the principal investigator for three forest dynamics plots in the American West through the Smithsonian network. How To Create Your Own Holiday Scent Memories What smells do you associate with the winter holiday season? Maybe it’s woodsmoke, cinnamon, or the ubiquitous scent of pine. Whatever fragrances you find festive, chances are good they’re strongly tied to memories of holidays past. Science educator Jennifer Powers returns to explain this enduring connection between scent and memory in the brain. She walks guest host John Dankosky through how to capture custom combinations of memorable holiday scents in your home this season.   Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm John Dancosky. I'm in for Ira Flato this week. Big trees are incredibly important to forest ecosystems, capturing carbon, housing animals, propelling new tree growth and providing much-needed shade. But when I say big trees, you might be thinking about the biggest trees, you know, giant sequoias or redwoods, trees that can grow to roughly 25 stories tall. Well, big trees are an essential part of every forest. These are considered the top 1% of trees. You know, giant sequoias or redwoods, trees that can grow to roughly 25 stories tall. Well, you're considered the top 1% of trees in each forest ecosystem, and they play an integral role in preserving forests all over the world. To help us better understand the wonderful world of big trees, his ecologist Jim Lutz. He's an associate professor of forest ecology at Utah State University in Logan, Utah. He also manages three forest dynamics plots in the American West through the Smithsonian Network.

Jim Lutz, welcome to Science Friday. Thanks so much for being here, and thanks for talking about big trees with us. Well, John, thanks for having me. Let's start off with some of the basics here. When we're talking about a big tree, what exactly are we talking about from your perspective? Well, when we look at forests around the world or even around the country, we have trees of different sizes. Every forest actually has big trees. A good guideline for where a big tree starts would be about two feet in diameter. But that's not really. always a great comparison. The best comparison is with the trees that are around it. And really, a big tree might be the ones that are the biggest 1% in any forest. So how old are the oldest

big trees or does it vary widely by the type of tree? Some of the very long-lived species like the giant sequoia or Douglas fir or even. even some oaks, can live hundreds or thousands of years, whereas some big trees, perhaps in eastern U.S. forest, might only be 100 years old or 150. Why is it that some trees get much, much bigger, while their neighbors of the same species stay relatively small? Well, this is what's really important and why big trees are important in every forest. So when trees start to grow, when trees are very small,

small, maybe they have sort of equal access to sunlight or to water or to resources. But over time, some trees become winners and some trees become losers. And once trees have fallen behind in the competition game, they sort of never can really catch up. So the bigger trees just keep getting bigger and they're crowding out the smaller trees around them. They're able to take in more of the stuff that allows them to just keep surviving and thriving. Right. In some forests, the limiting resource is light, and so trees that are bigger are also taller. In some forest, the limitation is water or nutrients. And big trees have bigger root systems, which allow them to compete both above ground and below ground. We talked earlier about why big trees are so important to forest ecosystems. Maybe you can just flesh that out a little bit more for us, Jimmy. What is it that makes them so important to ecosystems? So in terms of the tree population, big trees are proven.

They're proven successful. So in their genes is an adaptation for conditions that we see now and in the recent past. Also, big trees, they're very important to the future of the forest because they're producing many, many more seeds than those around them. One function that is really getting a lot of attention these days, is carbon sequestration, how much carbon the trees can hold. And big trees really hold disproportionately more of the carbon, primarily because, well, the carbon is mostly in wood, but a big tree is often also a tall tree. So it's occupying space in the forest that small trees just cannot be in.

So from a standpoint of carbon sequestration, if you have one really big, oak tree, it's going to perform better in terms of sequestering carbon than 10 or 15 little tiny oak trees? Absolutely. If we look at big trees and forests all around the world, from California to Cameroon, Michigan to Malaysia, the biggest 1% of trees hold 50% of the biomass in those forests. Another really interesting thing about big trees is what an excellent habitat they are for animals. And I know that you've looked at any number of birds and different types of mammals that live inside of trees. There are actually bats that live inside the bark of Douglas fir trees. I mean, there's some amazing things that trees are able to do in terms of providing housing for animals. Big trees, when they're living, provide a lot of habitat.

And then after big trees die, they become big snags, dead trees. trees, and then when they fall, they become big logs. Now, this is, you know, maybe over simplistic, but to make a big log on the forest floor, it takes a big tree first. And, you know, sometimes the habitat just can't be equaled by small trees. For example, if we take a large bird like an eagle and eagle nests are very, very large, it needs a tremendous tree just to be able to support a nest like that. So much of the world's ecosystems are in peril right now because of climate change and other

human cause factors. What is the state of the big tree in America or globally right now, Jim? Well, it's a mixed bag. The important thing to remember about a big tree is it takes a long time for a tree to get big. So what that means is over that long period of time, one century, two century, or three centuries, conditions need to be conducive to tree survival and growth. So if we're in a situation where conditions are changing very, very rapidly, the trees that are big right now might be having a harder time living in new conditions. and if trees can establish in those new conditions, it might take them centuries to, in turn, get really big. So around the world, we have been seeing decreases in the amount of big trees.

You know, a lot of that's because of human activity, either logging or land use conversion. but some of it is also due to changes in climate that are just making it a little harder for big trees to survive. Yeah, and those changes in climate include everything from a severe drought to increased risk of fire. If you have more wind events, you end up knocking over branches. It seems as though it's a pretty hard time to be a big tree in a forest right now because of all of these factors. It is, you know, especially in the West where we've been having. having a lot of very large high severity fires. It's been a tough time for the big trees.

You know, in the past, when forests were a little less dense and fires were smaller and less severe, big trees could survive those fires. Now in the West, we're seeing a lot of fires that are so hot that even the very largest trees are dying. And you've been studying the effect of big wildfires on some of the big, trees in places like Yosemite National Park. Maybe you can tell us a bit about how the aftermath of these fires have compared to how big trees have fared in the past.

Now, we had a fire in our large forest dynamics plot in Yosemite. When I say large, about 70 acres with 35,000 trees that we're tracking. And the fire that burned through that forest in 2013, it wasn't a big, severe patch that's killing a lot of trees. And in fact, when fire came through that forest, most of the big trees survived. Unfortunately, after 2013, we had a very, very severe drought. people say a millennial drought for California, one we haven't had for 500 or 1,000 years. And that drought itself weakened the trees, especially coming after the fire. And the drought or the drought in conjunction with beetle attacks did kill a lot of the larger trees.

So much of our conversation, and this isn't really surprising at a time of climate change, has been about the third. threats to big trees. But this is something that you study and you've made your life's work. I'd love to talk to you for the last couple of minutes about just why you love these trees so much. What is it that draws you to the biggest of the big trees? It's perhaps a little bit more than just purely scientific. When we walk out into a forest, we feel maybe awe in the presence of these large trees and we can find a connection with the world at large. And I think the large trees, because they're so majestic and because there's so much history, we know that they're so old,

they've seen so much. But I love that idea, too, of just the amount of history that is, that is imbued in these trees. Like when I've been to redwood forests and you put your hand on a redwood that you know that thousands of people over maybe a thousand of years have have seen and touched that that is really a remarkable thing for something that is that is living it's just a different time scale than us kind of puny humans are used to people all around the world have found this connection with big old trees and it is the case that trees are one of the few things, the few living things that lives so much longer than we do for for centuries, even millennia in some cases. And that's what makes it very, very hard to study forests

because our lifespan, our lifespan as people or as researchers is only such a small fraction of the lifespan of these big trees that to first approximation, it looks like they never change. If we go to the forest and we go next year, the tree may still be there and appearing exactly the same. But really, there is change. And if we watch enough trees, tens of thousands of trees over long enough periods of time, maybe we can understand these long-term trends and where the forests are going. I appreciate you spending some time with us today just talking about these majestic trees. I want to thank Jim Lutz, Associate Professor of Forest Ecology

at Utah State University. He's based in Logan, Utah. Thanks so much, Jim. And thank you, John. After the break, the holidays are a time for singing, but this holiday in particular is still a time for masks. So, can these two things coexist? Hmm. We'll find out

right after this. This is Science Friday. I'm John Dankoski in for Irafledo. One of the marks of the holiday season is folks coming together to raise their voices in song. But once again this year, some caution is still required, especially when it comes to airborne particles. We all know that masks can make voices a bit less distinct, though, so what is a vocalist to do? Thomas Moore is the Archibald-Granville-Busch Professor of Natural Science and a professor of physics at Rollins College in Winter Park, Florida.

He recently gave a presentation at the Acoustical Society meeting about masks and singing. Dr. Moore, welcome to Science Friday. Thanks so much for joining us. I appreciate it. Great to be here, John. Thanks. So we know that a person's voice sounds a bit different coming through a mask, but maybe you can explain, first of all, why? Well, there's actually two reasons why this happens. The first one is when you put a mask up close to your mouth,

then the material can interfere just with your lip movement, so the diction doesn't sound quite right. But the second and the more important problem is that you sound like you because of your oral cavity, that is, your throat, your head cavity, your sinuses and things like that. But when the sound comes out of your mouth, it meets the air and some of it gets reflected, just like with a musical instrument. If you put something in front of your mouth, that changes what the sound sees, if you don't mind me, anthropomorphizing the sound.

And so you sound different. This is the same reason that cheerleaders use megaphones. You want to change the resistance to the sound. going from your mouth into the air. Well, this happens inadvertently with masks, and it changes the way you sound. And so you started looking at different types of masks on singers. What did you find when you started to explore this?

Well, the first thing we found is that if you don't take into account whether the mask is making your voice softer or louder, if you just look at what it sounds like, up through about 1,000 hertz, which is where most people talk and sing, everything works fine. You don't get much change in the mask. But if you get above that level, then there are vast differences in the masks.

And you might think that, well, if we don't sing or talk above a thousand hertz or so, then it doesn't really matter, but it does because that's what makes you sound like you. It also gives you the sharpness, the T's, the S's, things like that. So when you put on a mask, it sounds muddy. And it sounds muddy because you've lost all those overtones or those higher harmonics. You haven't lost them. They're just down much, much lower than they should be. So we do actually have a couple of sound files that you recorded so that people can hear this difference.

And let's go through them. First of all, here is the singer that you recorded, and she's singing with no mask on whatsoever. Well, I forget every cloud I've ever seen. So they call me a cockade optimist, immature and incurably green. All the showtune fans will be out today. I really like the way she sounds. It's clear, and obviously she's not wearing anything on her face. So let's go to the next one here.

On this one, she's wearing what kind of mask? Just like a cloth mask, the kind that you get at the store? Yeah, it's a two-layer cloth mask, the kind that I wear every day. But this is a homemade, two-layer cloth mask. Lots of people wear them. Okay, let's listen. I forget every cloud. I've ever seen.

So they call me a cacide optimist, immature and incurably green. Wow, so you can really hear the difference. I mean, the first thing that I hear is it does sound very, very muffled, and you can't hear all the consonants. Her words aren't coming out very clearly. That's exactly right. And that's what happens when you knock off those higher frequencies.

It's sort of like listening to your stereo through the base only. You miss all those high frequencies. You don't sound like you. By the way, I would like to say that the soprano is Caitlin Moore, who's a professor here at Rollins College, and she sounds more like the first than the second. And she sounds really good, even through the mask. And I should also say that these were corrected to the same loudness

because the loudness is also something that is adjusted, right? I mean, when you have to sing through a mask, it is quieter than if you're singing without a mask. That's true. And that's actually one reason why we decided to use a professional singer rather than, say, a speaker like some other people have tested masks with. Because a professional singer can actually adjust a little bit to make herself sound like what she wants to sound like. And so that took out a lot of the variability that you'd find just due to the fact that the mask makes you not quite a lot. is loud. So the third example we have here is her singing with what's called a singer's mask. And I guess so that people have a visual of what this looks like. Explain what a singer's mask is and how it's different than the one that we might be wearing to the grocery store. Yeah, a singer's mask actually

has a frame that separates the cloth from the face. And so the mask actually is not touching the lips, first of all, and second of all, there's an area of several inches between where the mask starts and where the lips end. And so you've got this cavity in there that allows the air that you're when you're speaking, it allows your voice to hit the air more like it would in a room. It sort of looks like a duck bill. It looks a little funny, but it sounds a whole lot better. Let's listen to that one. ever seen. So they call me a cocky an optimist. They mature and incurably green. So what do you hear there that's different from the other mask? Well, from my standpoint,

the first thing you notice is it sounds more like a soprano, but you can hear that crispness in the consonants, as you said, that you aren't going to hear when you've got the other mask on. If I didn't know who was singing, I could clearly identify who it is. Is it different? Uh, slightly. If you get up to the very high frequencies, we notice a slight difference in the the amount of power in those higher frequencies, but nothing even close to what we get with the, just a cloth mask. With just a cloth mask, you get up around the 10 kHz region, which is fairly high, but it's important for the consonants to come out well. You'll see a drop off of 50 to 100 whereas with the singer's mask, you'll see a drop off of maybe one and a half.

Part of your research isn't just how things sound, but where the air is actually going. So maybe you can talk about that, the visualizations that you've made of where the air is going when you're wearing a mask in singing. Yeah, this is actually what we started looking at. We have a technique known as transmission electronic speckle pattern interferometry that can see, actually visualize the breath as it comes out of the mouth. And that's due to the temperature change between your breath and the ambient air. And so what we looked at was what does the breath look like when you sing without a mask?

Because we were concerned about, obviously, transmission of COVID amongst choirs. And it looks like what you'd expect. The air goes out. It goes out about three or four feet. It kind of starts to stop. But then you can easily see it rising because it's hotter than the air. when we put a mask on, any mask that we tested, because they don't make a good seal to the face, what happens is, is most of the exhaled aerosol goes out the sides and the top.

The mask will stop what we call ballistic particles, the kind of big spittle particles. But a lot of the stuff comes out the sides, the top, and the bottom. And at first we thought, well, that's a serious problem. We need to look at sealing these masks to the face. but in reality, unless you're in a medical situation, it's not a bad thing. What happens is the air comes out at the top or bottom or side of the mask. Because it is warmer than the ambient air, it immediately rises and it gets above head level. Furthermore, because it's close to the body, your body is hot and there's already rising air due to your body,

which we can see in using this technique. And so realistically, any of these masks will significantly help reduce the spread of COVID-19, but for a reason really maybe a little different than what we originally thought. It gets the aerosols up above the head. It's mixed in the ambient air. It's diluted. And so there's a much less probable transmission of the virus. So yeah, if you're singing in a choir in a big high ceiling to church, you can probably imagine that most of that breath is just going right up to the sky. It actually is. And it's a good thing. Unfortunately, most rehearsal and performance spaces are just like my house where they bring the air into the room

from above, and it exits somewhere lower. So in the long run, we probably ought to look at whether we can reverse that. Because in the next pandemic, or this one, if it ever ends, we need to keep the arts. And to keep the arts, we've got to have performance. And so a simple solution, if you could call it simple, is just to bring the air into the room from the bottom and exit from the top. Obviously, there are thermal considerations here. There aren't many air conditioning and heating people who would think that's a good idea. But those problems can be addressed. And I really think that if we just started thinking about bringing the air from the bottom and taking it out through the top, that yes, you could sing and a choir again. Now, you've also studied musicians playing wind

instruments too. I saw a video on your site of a flute is playing with an air shield and without. And in that example, the tone hardly changes at all, at least to my ear, but there's a big difference in how far the breath travels. Yeah, this is what you're talking about is just a sheet of acetate that goes in front of the mouth. So it hooks into the head joint and it has, as far as we can tell, no acoustic effect. Because it's beyond the point where the ear interacts with the flute, we can't hear the difference. However, what happens is because the flutist is breathing out, she's breathing right toward either the violins if it's an orchestra or the conductor, if it's a band. But by putting the sheet of acetate over the head joint,

the breath hits this piece of acetate and it goes straight up and down. Without it, it will go actually further than singing. But once you do this, the aerosol goes up or down. And just like with singing, it's entrained into the upward flow to the heat from the body, It's hot anyway, so it goes up. And we actually see it get way out of the, above the head. That's so interesting. Getting back to the masks quickly, in the singers that you worked with, did any of them say, yeah, this is pretty comfortable,

or this is really annoying to wear these singer's masks? Because I think the comfort of a musician is probably just as important as anything else if they want to perform at their best. Oh, I agree. They prefer the singer's mask to all the others. but I think that, you know, if you just ask them, I think that is due to the fact that they can hear themselves better and they sound better.

They look funny. There's no question about it. Obviously, they would rather sing without a mask. But given the choice, we've tested a tenor and the soprano. And, you know, of course they want to sing without a mask. But if you've got to have a mask to sing, you want a singer's mask. So if we're getting together for some sort of a holiday sing-along, going out Christmas caroling or something,

Do you have any tips for people about masking and not masking if you decided to go out and sing around this year? Yeah, truthfully, if you're outside, you probably don't have to worry about too much. You don't want to be close to someone where they're big particles, a little spittle particles can get to them. But outside, the ambient air is moving so much that it takes that aerosol and just whisks it away. I would prefer to sand upwind from somebody who's got COVID rather than downwind. But, you know, if you're going to wear a mask, wear something that gives you some room between the lips and the mask itself, and you'll sound great.

Thomas Moore is the Archibald-Granville-Busch Professor of Natural Science and a professor of physics at Rollins College in Winter Park, Florida. Thanks so much for talking with us. It was a pleasure, John. I'm John Dankosky, and this is Science Friday from WNYC Studios. For many people, this time of year is marked as much by festive fragrances as by colorful lights or family meals. That pine garland, those cinnamon cookies, or maybe your nose lights up at gingerbread, woodsmoker, mold wine. I know every year I can't wait for the first whiff of my wife's Black Forest Biscotti.

It takes me back to this kind of feeling of nostalgia and comfort. Now, back with us to talk about the staying power of smells and memories, and how we can recreate our favorite scent memories at home, it's science educator Jennifer Powers from the Oregon Museum of Science and Industry in Portland, Oregon. Welcome back to the show, Jennifer. Thank you so much. Explain for us, if you will, this connection between scent and memory. You're so right, because if we touch something,

we don't kind of have that same emotional or memory reaction than we have if we smell it, right? So that's because the way the signals travel to our brain is different. When we touch something, those signals travel directly to the thalamus, and that's responsible for sensory and motor signals. But when we smell something, that signal is carried through the amygdala, and the amygdala in our brain processes emotions. And then it also passes through the hippocampus, which is where we form memories in our brain. And so when we smell something that maybe we don't smell every day, day, you know, those special cookies or that special pie, you can be just hit with overwhelming

emotion and memory. What is a smell made of? What's entering my nose when I smell something? You mentioned two of kind of the most recognizable holiday smells, right? Cinnamon and then coniferous trees like pine or furs. Both of those kind of signature smells come from chemical compounds. For cinnamon, it's something called cinamaldehyde. And for pine trees and fir trees, it's a group of compounds called turpins. These substances easily release molecules as gases into the air. And so they're releasing these molecules and the molecules are floating around us. And that allows our nose, our olfactory receptors, to trap them and then send those smell signals to the brain. You brought us an activity that we can try at home with kids or adults for really capturing some of these favorite seasonal smells. So how do we do it?

So this is a really fun family activity. Definitely great for adults to be around because it does require a stove top and some hot utensils. Fair enough. But you're going to want to start with a pretty large pot on your stove and heat up a couple cups of water. And you're going to want to place an empty glass jar in the water, start heating it up. And then the fun part is you get to pick out something that smells good. Pine needles, for example, throw a bunch of pine needles into the water. And then you're going to cover the pot with an upside down lid.

And then you're going to place ice cubes on the top of that lid. And you're going to let everything simmer for about 10 minutes. And what's happening is as those items, those pine needles are heating up in the water, they're releasing all of those really super smelly molecules into the air and the gas and the steam is inside your pot. But then the ice, it hits the ice, which is cooling it down, causing all that water vapor and all those smelly molecules to condense back into a liquid that eventually falls into your empty jar in the center of the pot.

So after about 10 minutes, you can carefully remove the lid. Use tongs, very important, to take the very warm jar out of the pot. And then you'll find that the liquid you captured smells like the smelly stuff you put inside the pot. And it's just so fun and so cool. You could also keep experimenting with it, right? If you want to capture pine, scent and one jar, maybe cinnamon than the next. You could combine them together to make a super smell. You could even make a mystery smell. You could put something in there and try to fool your friends and family, see if they can guess what it is. I love this. Well, we're out of time, but for more on the connection of scent and memory and how to capture these memorable scents at home, you can visit

our webpage. It's sciencefriiday.com slash smells. Thanks so much for joining us once again, Jennifer. Of course. Thanks for having me. Jennifer Powers is a science educator at the Oregon Museum of Science and Industry in Portland. After the break, a doctor explores what he calls the hidden wonders of human biology. Hey, Ira here with an exciting message. Science Friday currently has a dollar-for-dollar donation match in effect. This means that any donation made through December 31st will be doubled, including yours. Now, I don't have to tell you that the need for Science Friday is stronger than ever.

So please head over to ScienceFriiday.com slash support to make a gift. We depend on the generosity of fans and listeners. Again, that's Science Friday.com slash support. And thanks. This is Science Friday. I'm John Dankoski. Most of us never get to see the inner workings of our bodies. Maybe we understand generally that the heart pumps blood through our circulatory system, how the liver filters that blood, and that the air we take into our lungs fills that blood with oxygen. And sometimes we get tiny glimpses when our bodily fluids make an appearance in the outside world, like a runny nose or a bleeding paper cut. But how well do we really understand what's happening inside? Our next guest is here to help us

with that. Internist and pediatrician, Dr. Jonathan Reisman, sees human anatomy as a reflection of the natural world. In medical school, he learned about each organ's function and its role within the body, and it struck them that each organ is like a different species thriving in its own specific habitat, all while working within the body's larger ecosystem. Dr. Reisman is the author of a new book called The Unseen Body, a doctor's journey through the hidden wonders of human anatomy. Jonathan Reisman, thanks so much for being here. Welcome to Science Friday.

Thank you for having me. What made you decide to write this book in this way, drawing parallels between the human body and the natural world? Well, before I ever started medical school, before I even wanted to be a doctor, I really fell in love with the natural world and obsessively learned everything I could about every species of plant, animal fungus. I absolutely loved exploring new patches of wood, traveling to new countries, understanding new natural environments, including how different human cultures related to those unique environments. And when I started medical school and started exploring the

human body, I basically, as you said, brought that same perspective of a naturalist and a traveler discovering some new terrain. In this case, that new terrain happened to be the human body. I started learning all of the different body parts, the internal organs, the bodily fluids. Each did seem like a species in a new environment. Each had its own appearance, its own daily life, its own particular behaviors, both in health and disease. And I really was, became obsessively interested in learning absolutely everything about the human body as I had about the natural world. I think it really crystallized for me when I understood that, as in the natural world, when we zoom out from examining an individual species and individual organism, we can then take in the ecological

perspective, the perspective of how individual species relate to each other and how every organism in a natural environment is interconnected in some way and each affects the other. That same perspective came to me about the human body, and I understood that seeing the different body parts from the ecological perspective, help me understand how the body works, and also help me understand a better perspective for practicing clinical medicine as well. As I hear you say this, and as I read your book, I guess I'm struck by the simplicity of that in how it might actually help us train physicians in the future, but that's not the way that medical school set up, is it?

Right. Well, there has been a trend towards more and more specialization as a way. our knowledge of the body, as our knowledge of disease of various body parts, and as an increase in available treatments and diagnostics, have only increased in recent decades. And to some extent, that is necessary. We do need specialists who understand the latest information about each organ, each body part. The amount of information out there is really staggering and no individual could really know it all. So we do need subspecialists. I, however, am a generalist, and I love coming at the body from that zoomed-out perspective to understand each of its parts as well as how

they interrelated. The stories in this book are often drawn from the first time that you encountered something, like the first time you saw an organ in the cadaver lab or the first time you diagnosed a heart attack. What is it about these firsts that were so important for you to document in this book? Just like when I was a lover of travel and exploring the natural world, it was always the first time that would be the most eye-opening. The first time I went to a new country, the first time I experienced a new culture. That first time when you're discovering in many ways a new world or a

whole new perspective is the most eye-opening, and that goes for travel, for exploring the natural and also for practicing medicine. I've since diagnosed heart attacks, too many to count, really. But it was that first time that really was kind of a milestone for me and was offered up this unique and new perspective on the body. Your first chapter in the book is about the throat. And you tell the story of a patient who's elderly and she'd been in and out of the hospital several times. And she was struggling with aspiration, food and water, getting stuck in her airway.

How did this experience make you think differently about the throat? When I was a medical student studying each body part, the throat was presented as a pretty stupidly designed body part. where the, you know, air and food go in to our bodies through the same entrance to the mouth. But in the throat, they must necessarily diverge food, drink, and saliva must go down the esophagus to the stomach. And air must go down the airway into the lungs. And it did seem rather stupid because one small slip-up, one incorrect swallow, if some food or drink goes down the windpipe into the lungs, to put it bluntly, you could die.

every single time we thoughtlessly swallow throughout the day, food and drink come very close to going into the windpipe, and it's this clunky, complicated mechanism of swallowing that keeps them out. Once I became a hospitalist, a physician working with hospitalized patients, I found that a lot of my elderly and infirm patients were suffering from basically the fallout of this seemingly flawed design. They were often developing aspiration pneumonia, because to make the throat's dangers even worse, the icing on the cake, if you will, is that the world's number one pneumonia-causing bacteria actually lives in our throats just above the entrance to the lungs. So when we do aspirate, that food, drink, or saliva can bring those bacteria down into the lungs. But when I cared for

this particular patient, she had very advanced dementia, could no longer speak, recognize her relatives or interact in any way. And she kept bouncing back to the hospital, getting one bout of aspiration pneumonia after the other. And it occurred to me that this very precarious design where we must juggle air and food perfectly throughout our lives, when it starts to break down in the elderly and infirm those with neurodegenerative conditions like dementia, Parkinson's, and strokes, in a way it almost offers the body a way out from prolonged suffering.

And I think that is why, as I learned in medical school, aspiration pneumonia used to be called old man's friend, because it often does provide this end, a dignified end to prolong suffering and illness. You tell another story about visiting the hospital's maintenance manager whose name is Richard, and he shows you how the building's plumbing worked. I'm wondering if you can talk about how this is similar and different to how blood flows to and from the heart, because we often think about this system as a type of plumbing. Right. And I think plumbing is a very good metaphor for understanding.

not only blood flow, but the flow of virtually all bodily fluids that flow through our insides or outward from the inside. The heart in particular, I think the cardiovascular system is how the heart pumps blood to all of our different body parts. Every little cell in the body must receive oxygen from the pumping heart in order to survive. And now the simplest view of plumbing is that some fluid is flowing through a tube, and it can either spring a leak or it, can become blocked. And so much of medicine actually is getting rid of those blocks, such as blood clots, you know, anything from gallstones to kidney stones can block up the flow of their respective fluid and cause tremendous pain and suffering. Unclogging those clogs is a big part of medicine.

But when you back up, again, taking in the bigger zoomed out view, it's not just an individual stream with a flow through it, but rather a branching system where different branches continue to branch further and further into smaller streams to feed every part of our body. But as you say, when you zoom way out, veins and arteries might look more like rivers and tributaries as you view them from space. Exactly. When I love to travel before medical school and still do, I really enjoy looking down at the earth from a plane.

And I found that the branching waterways that you see on the land was very similar to the branching, blood vessels that we see in our bodies and understanding how water relates to the shape of land, how terrain shapes the branching patterns of streams, but also how streams in turn erode and shape the land that give and take is very similar to what happens in our bodies and helps to understand disease and its treatment. You describe the body as a tube in the book, and it's something that I guess I've never really thought about. Can you explain that for me a bit? So when we start as a fertilized ovum in the body, we develop first into a cluster of cells and we flatten out into a little disc, basically. And as I say in the book, a few weeks into life, we roll into a little tube. And that

design stays with us for the rest of life. We start as this tiny little microscopic tube. And as we grow as a fetus and then grow as a human outside the womb, our body continues to enlarge and complicate the front end of the tube sprouts multiple different entrances through the nose, through the mouth, the esophagus and trachea split off from each other. And as we all know, the exit from that single tube also splits into exits for stool, for urine, and for the discharges of the gynecologic tract. And so as we grow into adults, we become a very complicated and adorned tube, basically, but that very basic blueprint still stays with us. And it explains a lot of what we find about the body's design.

I'm John Dankosky, and this is Science Friday from WNYC Studios. I'm talking with Dr. Jonathan Reisman. He's the author of The Unseen Body, a doctor's Journey Through the Hidden Wonders of Human Anatomy. You call urine in the book your favorite bodily fluid. So what's so special about urine? Great question. I'm sure most people have never thought about what their favorite bodily fluid is.

They're all simply repulsive forms of waste that have to be discarded. But as I tell in the urine chapter, when I started studying to become a doctor, I discovered that each bodily fluid is actually a language. And as a physician, each of those bodily fluids is communicating to me what is wrong with my patient's bodies. what is the cause of their symptom or the sign of their disease. And often making a diagnosis actually means learning to read those messages, learning to understand the language of each bodily fluid to interpret its consistency, its color, its amount, which often increases in illness, sometimes even its smell.

I found that urine is really the most fascinating of them all. Part of this is because it really provides a very impressive wealth of clinical information about my patient's bodies. I use urine every day to diagnose diseases, both those affecting the urinary tract, but really affecting the body as a whole in systemic illness, or even diseases that are affecting some body part far away from the kidneys and seemingly unrelated to the flow of urine altogether. So that for me is enough to already love urine as a really useful, a useful bodily fluid for me to help my patients.

But beyond that clinical utility, I found that urine carries this extra message. about where humanity comes from. So specifically our ancestors lived in the ocean before they crawled out onto dry land where we live now. And I discovered that the way kidneys work, the way they churn throughout our lives to extract urine from the bloodstream, the way they keep salt and water inside the body to prevent dehydration, but also the way they perfectly titrate salt levels in our bloodstream. they keep those salts in roughly the same proportions as the oceans that our ancestors used to live in. And to me, that highlighted the fact that without the kidneys, we could never have left the ocean. We continue to carry the ocean inside of each of us.

And the kidneys and the way they produce urine and the constant flow of urine is how that happens. And without it, we never could have adjusted to life on land. In the book, something else that I guess might be a little bit unpleasant to some people, you detail your experiences eating different animal organs like liver and lungs and brain. And it's somewhat counterintuitive, but it almost seems as though the more you learned about these body parts in cadaver labs, the more interesting you found them as potential food in animals. I wonder if you can talk more about that because it does strike me as, I don't know, maybe the more I knew about the human liver, the less I'd want to eat a chicken liver.

Right, and I perfectly understand that perspective, and I believe I had that perspective before going to medical school. Specifically, anatomy lab, where we dissect the cadaver, I would say, is where most people would go to lose their appetite, not to broaden it. For me, the opposite happened, however. There was one professor who really enjoyed pointing out different muscles inside the cadavers, the muscles that we were learning all about, and he would explain which one's correspondence. to different cuts of beef. That really fired my imagination and led me to visit a slaughterhouse and to start learning about butchering. And I ended up learning all about butchering and how to prepare and eat different organs around the same time that I was learning anatomy. And I found surprisingly that they complemented each other well. And for instance, learning all about the complexity of the

liver and how it oversees such a variety of important conditions. a variety of important balances in our body and how it keeps us healthy every moment. That fascination and that growing knowledge really led me to want to try it once again, even though in childhood I had never enjoyed it. And that fascination really helped me to enjoy eating it more. It is an acquired taste, but the medical knowledge, the anatomical and physiologic knowledge I was gaining helped me overcome that initial squeamishness. And the same was true for many body parts as well.

So most of us who aren't doctors haven't had this look inside the human body. I'm wondering how the rest of us who aren't either medical specialists or generalists like yourself, what they could gain from understanding how our bodies work just a little bit better. Well, I think one of the things that I loved most about learning about the human body was that there's so many levels at which you can understand the human body. there's the level of the individual, the whole body. You can zoom in to understand something on the level of an individual organ. You can zoom in further to the cellular level to see how that organ functions to keep us healthy.

You can even zoom in further to the molecular level to understand biochemistry. What I thought most fascinating was that often these different levels are intertwined in many ways. And sometimes when you zoom in to the molecular level, such as when you're understanding how the kidney titrates levels of salt in the blood on the molecular level. You're at the same time zooming out to understand the history of humanity and where we came from and how we evolved. So sometimes zooming all the way into this very specific microscopic level, in many ways for me men also zooming out to understand whether it's the history and evolution of humanity, whether it's the interconnected ecology of the natural world, whether it's how different cultures relate.

to their natural world and to their own bodies, how perspectives vary with culture. For me, that's the most fascinating. And I think understanding any part of the body necessarily leads to understanding it on the whole, as well as the universe outside of our bodies and how everything really is connected. Well, it's a fascinating look at the human body and our inner workings. I'd like to thank Dr. Jonathan Reisman. He's an internist and pediatrician. He's based in Philadelphia.

He's the author of The Unseen Body, a Doctor's Journey Through the Hidden Wonders, of human anatomy. Thanks so much for being here on Science Friday. I really appreciate it. Thank you so much for having me. If you missed any part of this program or you'd like to hear it again, you can subscribe to our podcasts, or you can ask your smart speaker to play Science Friday. Every day is now Science Friday. You can say hi to us on social media, Facebook, Twitter, Instagram, or email us. The address is SciFri at ScienceFri.com. I was back next week. I'm John Dankoski. Thank you.