Monday, February 15, 2016

Potato Osmosis activity

We talked about semi-permeable membranes and how nutrients, oxygen, and other things pass from the capillaries to the cells, or the alveoli to the capillaries, by diffusion or osmosis. This simple activity demonstrates the effects of osmosis. You cut a potato in half and put half of it in plain water and the other half in salt water. Then wait a few hours. (Put the cut side facing down; this picture shows it after we'd already turned it back over.) 

(White dish) Because there is a lower concentration of water in the salt water (the salt is "taking up" some of the space), the water in the potato cells moves out via osmosis. That makes the cells "floppy" or flaccid, since they have lost some of their water. You can feel that the potato is squishy and limp.

(Clear dish) The potato in the plain water stays firm and crisp. Because the concentration of water on the outside of the potato (in the dish) is the same as the concentration on the inside (in the cells), no osmosis occurs, and the cells stay firm and maintain their shape.

For another explanation of this, see here.

Thursday, February 11, 2016

Lung and Diaphragm Model

Here you see Malachi, looking thrilled (ha ha--this is actually his serious scientist face) demonstrating the balloon lung model. As you pull down on the "diaphragm" (bottom balloon), the air pressure changes in the chest cavity (bottle chamber), causing the lung (top balloon) to inflate with air. It's actually pretty cool to watch it working! Here are further instructions.

Tuesday, February 9, 2016

Heart Cookies

Not sure there is much to say about this. We made heart cookies. The little kids just used regular-shaped hearts and frosted them in sections with purple (unoxygenated blood) and pink (oxygenated blood) to show how blood flows through the heart. They had to show me the four chambers and describe the path of the circulation. (These cookies aren't pictured—the hearts below were just our leftovers!) Abe actually tried to shape his cookie into a real heart shape, though, and show the valves and the septum and so forth. I loved the way his cookie turned out!

Here are some other edible heart models you could make with graham crackers.

Monday, February 8, 2016

Blood Cells Under Microscope

After we did the blood typing activity we quickly smeared some of that nice blood onto a microscope slide so we could look at it! We have looked at blood cells before and they're very interesting, but it is harder than you think to get liquid blood! I've tried poking myself with a pin lots of times and I just can't get any blood (my survival instincts won't let me draw blood, I guess!). When I went to donate blood, I actually asked the nurse if I could have one of those little finger-pokers to use later, so I've got that one in reserve! But anyway, we already had some blood after blood-typing, so we leapt at the opportunity. :)

We're no experts in microscopy, so I'm not sure I can describe all the things we're seeing here, but you can definitely see those little flat/round cells! I am not sure if you can tell the red blood cells from the white? The white are bigger, we know. We thought we were picking out some differences but just weren't sure. And of course, my little iPhone photos don't really do justice to what we were seeing. It's hard to get in position a good picture without some sort of attachment for the phone!
We thought maybe that green triangle thing in the bottom left corner was a platelet?
And here is the blood as it was drying and starting to clot.

Friday, February 5, 2016

Blood typing activity

You know what's really fun? Testing your blood to find out what type it is. I already knew my blood type, but I wanted to do this activity anyway because its so fun smearing your blood around on the little test circle and seeing it clot (or not)! I highly recommend it.

And since none of the kids knew their blood types, it was extra fun to find them out! I ordered these blood typing kits from Amazon (the five-pack) and we would have happily used a couple more. They are very simple to use; just make sure you read the instructions and have everything set out and ready before you start.
I told the kids the finger-prick wouldn't hurt. And it didn't. But some of them were a bit offended by it anyway. (Here is Daisy pretending to be offended.) It did help to soak the fingers in warm water first so the blood would flow. Although with Abe, our first subject, the blood flowed a little TOO well and got everywhere! So we soaked the later kids for a little less time. You really don't need much blood. You don't need to saturate the entire circle with blood like they do for an infant PKU test. You just need enough to react with the antigen.
And here are the finished samples! Kind of fun to have them all collected on little cards like that.

Wednesday, February 3, 2016

Cardiovascular System Unit Study and Lesson Plan

This unit had a lot of content but very few pictures, for some reason. I do have a few other posts I will put up, but I'll link most of the videos and other content we used here.

Also, we combined a short treatment of the immune system with this unit, since the blood cells play such a big role. We talked about viruses and bacteria, and immune response. We may study that more fully in the future.

First and foremost, I MUST mention this group of videos that the children LOVED. At first they just thought the videos were silly. They kept saying things like, "Hey, the blood cells can't fly in little ships!" "Hey, germs don't say 'heh heh heh'!"—and so forth. But then the children caught the spirit of the thing and began to love the videos with a deep and abiding love. It seems like maybe the episodes are from a British TV program called "Once Upon a Time Life"? I'm not totally sure. There are other episodes that show other parts of the body, but we just focused on the applicable ones to this unit. We got to know and love all the characters quite a bit. The action is kind of slow but it's all part of the charm! As is the music. And the explanations are actually quite good.

Here are the episodes we watched (I'm just linking Part I of each episode, but parts 2 and 3 for each one should come up on the "other videos" menu at the right side of your screen. Or maybe you can just search online for "once upon a time life" and you'll find whole episodes somewhere. Each episode is about 30 minutes long).

Other than these gems, we also liked:
and this (annoying, but understandable) video about blood types

Here are instructions on how to make a simple stethoscope. This totally didn't work for us, but maybe it will for you! Luckily we had this stethoscope of our own and the children enjoyed listening to each others' hearts with it.

Here you can hear the sounds of various heart murmurs. It's amazing that doctors can hear and distinguish these!

Another thing that didn't work for us: this heart pump model with the four soda bottles. Maybe our bottles were too small? Anyway, there's a whole good lesson plan with it, so this page is definitely worth a look.

Another heart pump model we didn't try.

You can make this model of a drop of blood.

This interactive site helps you visualize the size of a red blood cell (among other things)

Of course it's always nice to compare healthy lungs to smokers' lungs:
and here

I've always thought it was fascinating how heart cells can beat all by themselves, and then sync when they get in proximity to one another. You can see a video here.

For a field trip during this unit, I called the Red Cross to see if the children could come watch me donate blood. We set it up during a less-busy time of day, and they were really great to work with me and allow the children to be close by. Our nurse was great—explaining stuff to them, letting them feel my bag of blood, etc. I'm not very squeamish about it and I like donating blood, so I didn't mind. Of course, most of all, the children liked getting pretzels and juice afterwards (the nurse kindly said they could have some, even though THEY weren't the ones who did the donating!). :) You can find a place to donate blood on the Red Cross website.

And here's my Cardiovascular System Unit Pinterest page.
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