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Primary Science · Year 3Chapter 6 · Skeletons and muscles
Year 3 Science · Skeletons and muscles · Lesson 6.4

Year 3 Science: Muscles pull on bones

Part of the Year 3 Science skeletons and muscles chapter. Chapter overview · whole chapter on one page

6.4

Muscles pull on bones

Year 3
A2: muscles for movement; muscles are joined to bones by tendons, and a muscle can only pull
Story. Oliver makes a fist and says, “I can feel my arm working.” His grandad says, “That is your muscles pulling on your bones.” Oliver asks, “Can muscles push as well?” Grandad says, “Let’s find out.”

A muscle is a part of the body that can get shorter and pull. When a muscle gets shorter, it contracts. When it gets longer again, it relaxes.

Muscles are joined to bones by strong cords called tendons. When a muscle contracts, it pulls on the bone through its tendon, and the bone moves.

A muscle can only pull. It cannot push. So one muscle can move a bone one way, and a different muscle must move it back the other way. Section 6.5 shows how this works in the arm.

The muscle contracts,gets shorter and pullsthe bone up.A muscle cannot push.It can only pull, sothe bone does not go down.
Left: a muscle contracts, gets shorter and pulls the bone up. Right: a muscle cannot push the bone down.

Key ideas

  • A muscle is a part of the body that contracts (gets shorter) to pull on a bone.
  • A tendon is a strong cord that joins a muscle to a bone.
  • A muscle relaxes when it gets longer again.
  • A muscle can only pull. It cannot push.
Worked example 6.4.1
What is the strong cord that joins a muscle to a bone called? Write the word.

Method. Think about the cord that joins a muscle to a bone.

  1. Read the chapter. A strong cord that joins a muscle to a bone is called a tendon.
    tendon
  2. Name it. So the word is tendon.
    tendon
  3. Write the answer.
    tendon

Check. The tendon pulls the bone when the muscle contracts. ✓

Watch out. A tendon is not a bone. It is the cord between the muscle and the bone.

Worked example 6.4.2
When a muscle contracts, does it get shorter or longer? Write the word.

Method. Think about what contract means.

  1. Read the word. Contract means to get shorter.
    contract = shorter
  2. Write the answer. So a contracting muscle gets shorter.
    shorter
  3. Write the answer.
    shorter

Check. A muscle that contracts pulls the bone. ✓

Worked example 6.4.3
Can a muscle push a bone? Write yes or no.

Method. Think about what a muscle can do.

  1. Read the chapter. A muscle can only pull. It cannot push.
    only pull
  2. Write the answer. So a muscle cannot push a bone.
    no
  3. Write the answer.
    no

Check. A different muscle pulls the bone back. ✓

Watch out

Watch out: a muscle does not push a bone back into place. A different muscle pulls the bone back the other way.

Try it at home or school (with a grown-up). With a grown-up, hold one arm out in front of you and make a loose fist. Slowly make a tight fist, then open it again. Feel the muscles in your forearm get harder and softer. Do not squeeze hard.

Exam tip

Grown-up tip. Ask: “Which part of your arm got harder when you made a fist? What is the muscle joined to?” Let your child use the words contract and relax.

Exercise 6D  Muscles pull on bones

1
FWhen a muscle contracts, does it get shorter or longer? Write the word.
2
FWhich cord joins a muscle to a bone? Write the word.
3
FWhat word means a muscle getting longer again? Write the word.
4
FCan a muscle pull a bone? Write yes or no.
5
FCan a muscle push a bone? Write yes or no.
6
FFill in the gaps.
(a)A muscle is joined to a bone by a ___.
(b)When a muscle relaxes, it gets ___ again.
7
FFill in the gap: when a muscle contracts, it ___ on the bone through its tendon.
8
FTrue or false: when a muscle contracts, the bone it is joined to moves. Write true or false.
9
FTrue or false: a muscle can push a bone back to where it was. Write true or false.
10
PSOliver says his arm moved because the bone pushed the muscle. Is Oliver right? Write no or yes, and say why.
11
PSLook at the picture. When the muscle contracts, which way does the bone move: up or down? Write the word.
The muscle contracts,gets shorter and pullsthe bone up.A muscle cannot push.It can only pull, sothe bone does not go down.
12
PSWorking scientifically. Ruby wants to find out what a muscle does when it contracts. Describe one way she could find out, using her own arm. Write one sentence.
13
RExplain why a muscle needs a tendon to move a bone. Write one sentence.

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