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Lesson 12 – When a Bone Breaks

Read About When a Bone Breaks


Read the vocabulary terms to understand the reading better.


Bones are hard, rigid structures that make up the skeletons of vertebrates.


A cast is a hard, solid device made of plaster and fabric or of fibreglass that keeps a broken bone in the correct place and doesn’t allow it to move while it heals.


Plaster is sand, water, and a mineral called gypsum, that are mixed to form a paste to be spread over fabric and allowed to harden to support and protect a broken bone while it heals.


An x-ray is a quick, painless procedure that produces images of the structures inside the body, especially of the bones.

Bones Are Strong

Bones can stand up to quite a bit of force. Think about the last time you tripped and fell. Your body hit the ground with a lot of force. You probably did not break a bone because your bones were strong enough to stand up to the force.

Did you know that bones can bend? Bones can bend a little when a strong force acts on them. If the bone bends too much, it will break. Think about breaking a pencil. When you first start to put force on a pencil, it will bend a little. If you increase the force you put on the pencil, it will break.

Setting Broken Bones

A doctor will take an X-ray to find out if a bone is broken. The X-ray also tells the doctor how to set a broken bone. The doctor has to move the pieces of the broken bone back to their normal position. Setting a broken bone is a way to make sure the bone heals properly.

To learn more about X-rays, watch the video by TED-Ed on Youtube.

Putting a Cast Around a Broken Bone

Once the broken bone has been set, it is important to keep the two broken pieces in the proper position until the bone is completely healed. Doctors often use a cast to make sure that the broken pieces of bone do not move while they heal.

A cast is a hard structure that goes on the outside of the body, over the broken bone. Some casts are made of bandages soaked in plaster. When the plaster dries, the cast is hard and stiff. Some casts are made of hard plastic.

A Broken Bone Heals Itself

It can take from one to two months for a broken bone to heal. The bone makes many new cells to heal the break. These cells act like glue—they hold the broken pieces together and slowly make the bone as good as new.

Now Show What You Know!

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