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Human Biology: Bones and the Skeletal System

Anatomy of Bones


We began our study of the skeletal system. Using the example at Angelicscaliwags, we began making a model of a bone, showing all the layers. One of my students has always had a particular interest in bones, so he loved it. We began with stringing red and blue pieces of yarn in a red straw. This represents the blood vessels running down the red bone marrow. Next the straw was rolled in a bit of yellow wool roving  to represent the yellow bone marrow. This was wrapped in a sponge that had a scrubbing pad attached. The yellow part represents the spongy bone and the green part represents the compact bone. It was all stuffed into an empty paper-towel roll, which represents the compact bone.

What Makes Bones Strong?

Even though bones are very light, they are also very strong. However, how strong they are depends on how much of the mineral calcium carbonate they contain. 


Dried, clean chicken bone (a leg or wing bone)
A glass
White vinegar

Without breaking the bone, hold the bone and try to bend it - don't force it to bend; or it will break! Notice how stiff the bone is.
Place the chicken bone in the glass and fill it with vinegar.
Let the bone soak for 2-3 days, then pour out the vinegar.
Add fresh vinegar and let it soak for about 2 more days.
After the 4th or 5th day of soaking, take the bone out and dry it off. 
Now try bending the bone without breaking it. What do you notice? How does it feel different from before you soaked it in vinegar?

The Science Behind It

Bones are made of calcium carbonate and a soft material called collagen. When the chicken bone was placed in the glass of vinegar, the acid in the vinegar dissolved the calcium carbonate so that only collagen was left. Calcium, the mineral in calcium carbonate, is needed to make our bones strong. A few foods that contain a lot of calcium are milk, cheese, soy products, beans, almonds, and orange juice.

The Skeleton

One student also made a paper model of the whole skeleton from Donald Silver's The Body Book: Easy-to-Make Hands-on Models That Teach. I had him learn the names of the bones, using a picture to reference.

Backbones and Flexibility

What gives you the ability to be flexible?

 Drinking straw
Pipe cleaner
Scissors

 Thread the pipe cleaner through the straw. Then gently try to bend the pipe cleaner where it is covered in the straw. Does the pipe cleaner bend much?
Take the pipe cleaner out of the straw and cut the straw into pieces that are about one inch long. Thread the pieces of the straw onto the pipe cleaner so that they are touching each other.
Now gently bend the pipe cleaner again. How easily does it bend?

The Science Behind It

The small pieces of straw are very similar to how our bodies' backbone is structured. Your spine is made up of small bones stacked on top of each other with the spinal cord threaded through them. Like the pipe cleaner, you can bend your back forward and backward, side to side, and even rotate in a circle. 
Paper Joint models from Donald Silver's The Body Book: Easy-to-Make Hands-on Models That Teach

Your body has a lot of other joints, too. In fact, everywhere that bones connect inside of your body has joints. We learned that their are several kinds of joints according to how one bone connects to another, and the flexibility they need to have.

Intervertebral discs (or intervertebral fibrocartilage)

We took wagon wheel pasta and gummy Lifesavers and made a spinal column. 
We discussed how the bones of the spinal column have squishy discs between them that help the spine to be flexible and yet strong.

What Do Bones Do?

We talked about the fluid surrounding the brain in the skull. We took an egg in the shell and put it in a small container and shook it. The egg cracked. Then we threw away the egg and washed out the container. We put another egg in the container but this time we filled the space around the egg with water. We put the top on again and shook the container as we had done before, and the egg remained uncracked. Just as the water protected the egg from cracking, the fluid in our skull that protects the brain.


The Bones of the Hand

Our amazing hands have 27 bones! A really fun way to learn about them is to make cookie models of them as suggested by Almost Unschoolers. She gives great instructions on how to make eight small balls of white sugar cookie dough, pushed together, for the carpals of each hand. Then they made the long thin metacarpals with pink tinted sugar cookie dough, the proximal phalanges with yellow tinted sugar cookie dough, the middle phalanges with purple tinted cookie dough and the distal phalanges with blue tinted dough.

 Pasta Bones
And lastly, Martha Stewart created this idea for making bone pictures out of a variety of pasta. It was originally made for a Halloween decoration, but they would make good bone pictures for study.


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