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The Inside of Me -- The Parts I Can't See


The framework inside of me is called my skeleton.  My skeleton is made up of 206 bones.  Without my bones, I'd be squishy like a jellyfish and I wouldn't be able to move around.  When I was first born, I had over 300 bones, but as I grew up some of the bones attached together to form larger bones.  By the time we're fully grown, we only have 206 bones!

Our bones do four important things:  they provide stability to our bodies, they give strength so we can carry weight, they manufacture our red blood cells and they provide protection to other parts of our insides.  One of the boniest parts of our body is our head -- the group of bones in our head is called our skull.  We have so much bone in our skull to protect a very important part of us:  our brain.

Our bones have a lot of a mineral called calcium in them.  Drinking milk provides us with calcium to keep our bones strong.  The outside of our bones are very hard, but they are softer on the inside.  The soft inside of our bones is called our bone marrow.  It is the marrow in our large bones that makes our red blood cells.

Each place where our bones meet and bend is called a joint.  The bones in our jaw and in our fingers have hinge joints.  These let our fingers pinch together and hold things.  In our hips, we have ball and socket joints.  These let our hips move all different ways...  Dance, baby, dance!  The joints in our spine are called slide joints.  We even have joints in our bodies that don't move at all -- these are called fixed joints like the ones in our heads.

Our bones come in all shapes and sizes.  The biggest one is the bone in our leg -- it is called the femurs.  The smallest bone is one of the three bones in our ear -- it is called the stirrup.  The other bones in our ear are called the hammer and the anvil -- they're very small too.  As we get older our bones get bigger.  This is how we grow!



Our muscles work together with my bones to allow us to move.  We have more than 650 muscles in our body!

Muscles are like elastic bands, they stretch out long and then snap back short again.  Muscles work together in groups -- as some stretch out others tighten up, allowing us to move our bodies around.  For example, our tricep and bicep muscles work together to flex our arm.  When you bend your arm, your bicep muscle gets short and your tricep muscle gets long.  When you straighten your arm, your bicep muscle gets long and your tricep muscle gets short.

Many of our muscles are attached to our bones.  The part that attaches them is called a tendon.  These are the muscles that help me move.  We also have muscles that do other things.  Our heart is a muscle that pumps blood through our body.  There are muscles in our stomach that help us digest our food.  There are muscles in our chest that help us breathe.  These muscles are not attached to bones and do not have tendons. 

The muscles attached to our bones tend to be voluntary muscles -- we have to think and decide to move them...  We can stop them and start them.  The other muscles tend to be involuntary muscles -- our heart pumps and our stomach digests food without us ever thinking about it.  We can't "decide" to stop using these muscles.

If we don't use our muscles, they grow weaker.  It's important to move around and get some exercise every day to keep our muscles strong and healthy.  When we use our muscles they get warm, so if you're ever cold in the winter move around and it will warm you up! 

My favourite muscles are the ones in my face.  They let me smile and wink and make funny faces!  Did you know it takes 43 muscles to frown but only 17 muscles to smile?


Heart and Blood

Our heart is the strongest muscle in our body.  It pumps our blood all over our body through thousands of little tubes called veins and arteries.  It take about a minute for one drop of our blood to get to all parts of our body and then back to our heart again.  If you put your hand on your chest, you can feel your heart pumping!  If you want to feel how fast your heart is beating, you can feel it in your chest, your wrist or your neck.  Feeling the heart beat is called the pulse.  Can you find your pulse?

Our heart is about the same size ar our closed fist.  The right side of the heart receives blood from the rest of our body and pumps it into our lungs where oxygen is added to the blood.  The left side of the heart receives blood full of oxygen from the lungs and pumps it through the body, delivering the oxygen to all of the cells.

The blood leaving your heart is carried in arteries.  It is clean and travels to the different parts of our body carrying oxygen from my lungs to the cells of my body.  As it travels, my blood picks up waste -- carbon dioxide -- which it delivers to be cleaned.  The blood carrying waste travels through veins.

It is the red blood cells that carry oxygen to feed cells and carbon dioxide to be cleaned.  My blood also contains white blood cells.  I think these are the super heroes of my body.  White blood cells fight off germs and diseases like the flu and help keep me healthy.

Our bodies have between 2 and 4 litres of blood.  If we cut ourselves and lose some of our blood our bodies will produce more.  It is the marrow in our large bones that make new blood cells.  In the time it takes for me to count to 20, my bones can make 10 million new blood cells!



When we breathe, we take air in through our nose.  The moistness and tiny hairs in our nose catch dust and germs from the air and help keep our insides clean.  Once past our nose, the air travels down a tube in our throat called the trachea down into my lungs.

Underneath of our lungs is a strong muscle called the diaphram.  This muscle moves our chest in and out.  When our chest moves out, we breathe fresh air in -- this fresh air contains oxygen which my body needs.  When our chest moves in, we breathe used up air out -- this used air contains carbon dioxide which is waste our body produces.  This muscle is mostly involuntary (it moves without us thinking), but we are able to control it a little.  We can decide to take a deep breathe in or we can decide to hold our breathe for a little while.

There is a special group of bones in my body to protect my lungs and my heart.  These bones are called my ribs and they are arranged like a cage to protect my lungs and heart.


Brain and Nervous System

Our brains are in charge of giving orders to the rest of our bodies.  Our brain is inside our skull in our heads.  It makes our bodies move, it lets us think, feel and remember and it keeps our involuntary muscles like our hearts working.

Inside our bodies are thousands of nerves that carry messages from our brain to the other parts of our bodies.  Nerves from our eyes, ears, nose, tongue and skin carry the information our five senses collect for us to our brain -- what do we see, hear, smell, taste and feel.  With this information, our brain tells us about the messages and we make decisions and have feelings and thoughts.

The most important path for messages between the brain and the rest of our bodies is through the spinal cord.  The spinal cord is a bundle of nerves protected by the spine.  These messages travel very quickly so that we can react to the world around us.

My brain is where I think and feel.  I figure out puzzles in my brain.  I feel happy or sad inside my brain.  My brain is where I get scared or come up with a new idea or play make believe.

My brain is one of my favourite parts of what makes me, ME!


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