Friday, 8 March 2013

Learning About the Cardiovascular System

A friend asked me to review a curriculum on the cardiovascular system for her website, and although I wasn't sold on the downloadable lesson plans and resources, the girls were enthusiastic about the topic. I searched around on the net and ransacked my own creativity and came up with some resources, experiments and activities to bring it alive.
I started out by asking them what they already knew and it was really interesting listening to their answers. Eve's answer was long, contained lots of part pieces of information, and showed that she had a good overall grasp of what the cardiovascular system does. Faith's answer was shorter, and contained less detail but was much more accurate. Their answers were really representative of how they learn best - Eve likes to have 'the big picture' then fill in the details whereas Faith prefers to know small parts and add them together to make a big picture. I asked them then what they wanted to know about the CV system, they said they wanted to know why the blood coming back to the heart has no oxygen, how the heart moves and how blood gets back up the veins without falling down again. This concept came from the curriculum I was reviewing and I liked the idea of starting this way, and I think I will use it again.
Making a model of a drop of blood based on this idea
We started out talking about the blood, and it's main components of plasma (yellowish oil), red blood cells (kidney beans), platelets (red lentils) and white blood cells (butter beans). As the girls took turns to put them in, we discussed what each of the components did and so built up knowledge of the main functions of the blood (transport of oxygen and nutrients, clotting to slow and stop blood loss, fighting infection). Talking about all these things naturally led to us discussing the structure of the heart in some detail, how blood flows through it and what happens in the lungs.
The girls took turns to draw around each other to make a body diagram......
Diagram of the heart from here
I later discovered this site which has a complete set of full sized organs to print and assemble on your body outline!

....... and they then added a diagram of the heart and we looked closely to follow the route of the blood through the structures, with the girls getting used to the terminology. That led us on to discussing the differences between arteries and veins, their different roles and why arteries are buried deeper inside the limbs than veins.
We looked closely at our wrists and hands to see what veins we could see, I showed the girls how the artery in my wrist pulses, and we talked about what would happen if you cut an artery by accident or cut a vein. They used a lot of logic and applied things we'd talked about before to build their ideas and answers, it was great!
We added lungs made from over sized bubble wrap, and the main arteries and veins of the heart using blue and red pipe cleaners to demonstrate where they went.
Idris worked hard on copying the girl's 'listening poses' , see how intently he is looking at Faith?..... he was very funny bless him!
Another day we added the digestive system and liver onto the body diagrams and talked about how the blood collected nutrients from the small intestines and why and how the blood needed to be cleaned. The girls worked most of it out for themselves with a few leading questions to get them to think in the right directions.
A very simple demonstration with water in a straw showed the difference between having and not having a valve. We sucked up water into the straw, lifted it out and watched the water drain out immediately. Next we sucked water up, pinched the straw as hard as we could before lifting it out and saw that the water stayed put, so showing what valves do in a very basic way.  
As a finale to the fortnight of exploring the cardiovascular system, we looked at a heart. I had ordered a pig's heart from the butcher but none came so we had an Ox heart instead! It was HUGE, but was better in the end as being so large enabled us to see the structures inside really clearly. In the photo above, we were looking at the difference in muscle size between the left and right ventricles and applying what we knew about why they were different.
Here we looked from above down into the atria (which had been cut through before we got the heart) and saw the top of the heart valves.......
 .........then had a look from below at how the valve was tethered to the muscle.......
...... and |I was able to show them how the back force of the blood would snap the valve shut and stop the blood from flowing back into the atria, rather than going round the body. We could just about see the start of the aortic arch leading from the ventricle, but sadly the rest of the veins and arteries were missing. We did have a look at the criss cross of vessels on the outside of the heart and talk about why the heart itself needed a good blood supply.
It was a really enjoyable fortnight of science sessions about the cardiovascular system and the girls are keen to do more, they want to find out about bones next and add them to their body outlines!

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