Can you imagine your body without bones?! In fact, the average adult has 206 of them!
Your bones form a skeleton that protects your organs, helps you move, and gives your body the support it needs. When you think of these bones, do you picture them as hard and lifeless? You may be surprised to learn that your bones are very much alive, and they're made of both hard AND soft tissue!
Let's start with two crucial substances found in the tissue of your bones: a mineral called calcium phosphate and a protein called collagen, which work together to make your bones strong and flexible.
Did you know that your bones have layers?! The thin outer layer of bone is called the periosteum, and it includes your nerves and blood vessels. Next there's the compact bone, which is smooth, hard, and white; just the way we picture our bones to be! There is also a layer of spongy, or cancellous, bone, which has a sponge-like appearance, is softer than the compact bone, but is still sturdy! Finally, most bones have a soft, inner core. This is your bone marrow, and it's responsible for making your blood cells, which carry oxygen throughout the body and fight infection, among other important jobs.
(by Mya Kagan)
As you've just learned, your bones have different layers! Because your bones aren't packed solid with hard material all the way through, they are fairly lightweight. Can you imagine if your bones were heavy and compact like a bowling ball?! Heavy bones would put stress on your muscles. It's a good thing your bones are the perfect size and weight for your body!