Science 4th grade | UNIT 1: Humans and animals 1.3 Why do we need a skeleton?
Skeletons grow
We grow and get bigger because our skeleton grows. An adult's skeleton is much bigger than a child's skeleton. An adult's skeleton has stopped growing.
Activity 1.3 (Comparing bone sizes)
You will need: a tape measure
Using a tape measure, measure the length of your:
• upper arm bone • thigh bone • shin bone.
Measure the length of the cut-outs of the same bones on your teacher.
Record your measurements in a table like this one.
| Length in cm | Bone | |
| Teacher | Me | |
| upper arm bone | ||
| thigh bone | ||
| shin bone | ||
Whose bones are longer?
Predict what you think the length of a teenager's bones would be and say why.
Sometimes we fall or have accidents and break our bones. A broken bone is called a fracture. Doctors take a special photo called an X-ray to see if a bone is broken or not. X-rays are photos that let us see inside our bodies.
Sometimes we fall or have accidents and break our bones. A broken bone is called a fracture. Doctors take a special photo called an X-ray to see if a bone is broken or not. X-rays are photos that let us see inside our bodies.
Skeletons support and protect
Our skeleton supports our body. It makes a strong frame inside the body. We cannot squash our body easily because of our skeleton. It gives our body shape and makes it firm. Our skeleton also protects our organs.
Do all animals have skeletons?
Not all animals have a skeleton. Worms and jellyfish do not have a skeleton. An animal with no skeleton is called an invertebrate.
Questions
1) What would happen to a baby if its skeleton did not grow?
2) Why do broken bones mend?