Tuesday, October 11, 2011

Lungs and Air

I've got my 3.75 year old twins at home instead of in preschool for a short period of time, this is Day 4 of my Big Preschool at Home project- I'm hoping to keep up with the blogging, both as a record and to help anyone else who is planning something similar or wants to supplement preschool with some discovery learning and science activities.

Upside Down Lungs = Tree!
Breathing and lungs did not lend themselves to preschool projects quite as easily as the heart or the GI system. We talked about air coming in, and I flipped over diagrams of the lungs so that they really looked like trees. I was surprised at what a difference that made- it was as though when I first started talking about the windpipe as a large tube, like a trunk, and how it branched and each branching tube got smaller, just like a tree, they were just staring at me blankly, but after I showed them the lungs actually looking like a tree they could visualize it.

The other analogy that I used was for the alveoli. I asked them to imagine a balloon tree, so that at the end of each little "twig" in the lung tree, there was a bunch of little balloon instead of leaves. Alveoli are often described as looking like grapes in anatomy classes and texts, but while they do look like grapes, that image of solid tissue (combined especially with the fact that to the naked eye lungs look solid rather than hollow) make eventual understanding of the function of the lungs that much more difficult. Plus, with young kids, balloons are way more interesting than grapes.

At this point I feel like I need to talk about why I am teaching my preschoolers about stuff that lots of adults don't know. I don't really have a good answer except "Why not?" They seem to love learning how things work, the natural curiosity of the age can be applied to a specific subject (like physiology) rather than being generalized in a series of random (and never-ending!) "Why?" questions- all it takes is just introducing a topic and getting them excited. It's like vocabulary- I could use the word nice to describe a desired behavior and while praising specific incidences, but "nice" is a pretty vague word, and the kids hear it to describe pleasant weather, as an exclamation along the lines of "rad!" and to describe a good steak. So I use the word considerate, and tell them how "consider" means to think, and how we want to think about how our actions affect those around us, and (since I know they are three and learn from concrete examples) then we talk about the real world, all from the perspective of being considerate: When you snatch a toy from Alex, how does it make him feel? Is it considerate to snatch? When you throw trash from the window of a moving car, what happens to it? Who cleans it up? Does it mess up nature? So is it considerate to litter? And pretty soon they are noticing the world through a new lens, one that is more nuanced and more practically applicable than the simpler concept of "nice". They can learn it, I mean, learning the meaning of words (or the way the world works) is a complex business which they are primed for right now, why not go ahead and expose them to a more thorough toolbox and let them use as much of that awesome ability to learn new concepts as possible? 

Maybe some of it will stick, maybe it will make biology easier for them (I kinda doubt that). Or maybe it will function as a cool foundation for developing investigative, scientific minds. Or maybe it will get them excited about asking questions and trying to figure out answers to those questions- wait those last two are the same thing: SCIENCE! Maybe it will prevent them from feeling like science is scary, as so many people do, just by taking away the barrier of scientific jargon. Or maybe it won't do a damn thing except help me, as a parent, come up with some fun stuff to do during these infuriating, amazing, exhausting, beautiful, long and over-so-fast days of raising young children. 

Back to the project!

We had a good foundation with the fact that the blood needs to bring air to the cells. And they knew enough to know that we breathe in through our lungs to get air. We busted out the stethoscope again and I traced where the air went in, down the trachea and into the lungs, and reminded them about how the ribs formed a protective cage around the lungs and heart. 

Then I got a balloon out and blew it up and deflated it several times, asking them to tell me what is inside of the balloon when it is full. We talked more about the lungs being an upside down balloon tree, and I asked them to take deep breaths and imagine that every time they did all the balloons on the tree got blown up super big, then on every breath out, they deflated. When the balloons were blown up, I continued, the blood could come by and grab some air from them and take it to the cells. 

We looked at some pictures of the alveoli capillaries, and I showed them how the blood came in without oxygen (blue), picked up air from the balloons, and then left filled with oxygen (red). Not sure if any of that part sunk in, but they loved the pictures and tracing the path of the blood from blue to red with their fingers.

The project I decided to do was about how we breathe in and out, rather than what happens to the air inside our body. It was not ideal, given the emphasis I placed on lung function in my week-long lesson arc- that is, I had kind of bound the whole week together on circulation not the mechanical way that we breathe. Hey, anyone who isn't as much of a physiology nerd as me, want a one sentence explanation of how we breathe? The diaphragm muscle moves down, creating space and a pressure vaccum that allows the lungs to expand, the alveoli fill up with air due to a pressure differential rather then being inflated like a balloon or a car tire, does that make sense? However, I was totally stumped how to make a hands-on project showing something like oxygen transfer. We could have played a game with trains to get into the idea of transportation, but I decided to go with a project where we built a little model of breathing because it seemed like it would hold the kids' interest more. In hindsight, I'm not sure if that's true!

We made a model of a lung that shows how when the diaphragm moves, air gets pulled in to the alveoli- represented by the balloon inflating inside the bottle. There are a ton of instructions for this project online, some listed below. Here's how I did it:


2 balloons (good to have spares in case you butcher your first one)
Small plastic bottle
duct tape


  1. Take the bottle and cut the bottom off.
  2. Without inflating, tie one of the balloons off, then cut the top off of that balloon. Try fitting the cut top of the balloon over the cut bottom of the bottle. Cut a little less off next time if it doesn't fit or leaves only a tiny bit of the knotted balloon stem dangling from the bottom- you'll need to pull on that knotted end to create negative pressure in a minute.
  3. Duct tape the cut balloon to the bottom of the bottle. Make sure to seal it well, because any air leaks will ruin the effect.
  4. Take the second balloon and inflate it a couple of times- the balloon will inflate more easily during the experiment after being stretched. Then stick the straw into the balloon and secure with duct tape, again, being careful to seal well to prevent air leaks. Try blowing it up with the straw to check for leaks. You can stop right here and let the kids play with this contraption, they'll be able to blow up balloons like this even as little kids, which is so fun for them!
  5. Insert the balloon side into the neck of the bottle and secure with duct tape, making sure there are no air leaks, but leaving the straw end free.

Have the kids look at the deflated balloon inside the bottle- this is the lungs/alveoli. The bottle itself is the chest cavity/ribs and the cut and tied off balloon at the bottom is the diaphragm muscle.

Watch the lung-balloon carefully as you pull the diaphragm-balloon down and away from the chest-bottle: It will inflate, just like the lungs do when the diaphragm contracts and flattens, creating more space in the chest cavity, causing negative pressure and air is sucked right into the lungs.

Now, the balloon-lung may only inflate a little, possibly only enough to get rid of the folds of the balloon- a smaller lung-balloon or a large chest-bottle and diaphragm might make it more obvious. We used a small 16 oz. water bottle and two 10" balloons just because I had them lying around. If you run into problems with the lung not obviously expanding, check for air leaks, then try sucking on the straw so that the balloon has no residual air at all, then the difference when some air gets "breathed" in will be more obvious.

My kid enjoyed the project, but as I said, the meat of the lesson may have been over their head. They've definitely internalized the process of breathe in air with the lungs -> blood takes air from lungs and transports it to the cells, and that cells need more air when they are exercising (big ups to my husband; when the kids told him they learned about the lungs and breathing, he asked them about times that they got out of breath and how running around made them feel- I totally spaced on that angle, which has proven to be a great teaching tool that we can talk about all the time while playing!)

And the part of the project that was the most fun for the kids? Blowing up the lung balloon with the straw!

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