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KS2 Science Guide · Year 5–6 · Free lesson

The Circulatory System

The heart beats around 100,000 times a day, pushing blood to collect oxygen from the lungs and deliver it everywhere. This lesson explains the heart, blood and vessels — and why exercise speeds it all up.

SC6The Circulatory System
The heart, blood and a double loop.
The circulatory system carries oxygen and nutrients around the body — pumped by the heart.
The heart's double pump.
❤️ Heart
A muscle that pumps blood non-stop. It sends blood to the LUNGS to collect oxygen, then around the whole BODY.
🩸 Blood
Carries oxygen, nutrients and waste. Travels in tubes: arteries carry blood away from the heart, veins bring it back.
Blood picks up oxygen in the lungs, drops it off around the body, returns for more.
1

Learn the System

1The heart pumps.

It’s a muscular pump that never stops. Two sides: one sends blood to the lungs, one to the rest of the body.

❤️ the pump

2Blood collects oxygen in the lungs.

When you breathe in, oxygen crosses into the blood in the lungs. The blood carries it to every cell.

lungs → oxygen in blood

3Vessels carry blood everywhere.

Arteries carry blood AWAY from the heart; veins bring it BACK; tiny capillaries reach every cell.

arteries · veins · capillaries
💡 Key IdeaWe breathe to get oxygen into the blood, and the heart pumps that oxygen-rich blood to every cell — the two systems work as a team.
2

Worked Example

Why does your heart beat faster when you run?

Exercise
muscles work hard → need more oxygen & energy
→
Response
heart pumps faster to deliver oxygen quicker; you breathe faster too
→
✓ Result
more oxygen reaches the working muscles
3

Watch Out! Common Mistakes

✕
‘The heart makes oxygen.’

The lungs collect it! Oxygen comes from the air we breathe into our lungs. The heart pumps the oxygen-carrying blood — it doesn’t make oxygen.

✕
‘Blood is just red liquid.’

It’s a delivery service! Blood carries oxygen, nutrients, and takes away waste like carbon dioxide.

✕
Arteries and veins mixed up.

A for Away! Arteries carry blood Away from the heart; veins return it.

⬇ Cheat Sheet

THE CIRCULATORY SYSTEM
  1. The heart is a muscle that pumps blood non-stop.
  2. Blood collects oxygen in the lungs, delivers it around the body.
  3. Arteries carry blood away; veins bring it back.
  4. Exercise → heart and breathing speed up to deliver more oxygen.
Example: running → muscles need oxygen → heart beats faster.

📖 Continue Your Journey

✓ SC1 Classifying Living Things✓ SC2 Habitats and Adaptation✓ SC3 Food Chains and Webs✓ SC4 The Skeleton and Muscles✓ SC5 Digestion and TeethSC6 The Circulatory SystemSC7 Plants and PhotosynthesisSC8 Life Cycles and ReproductionSC9 States of Matter and the Water CycleSC10 Materials and Their PropertiesSC11 Reversible and Irreversible ChangesSC12 Forces and MagnetsSC13 Light and ShadowsSC14 SoundSC15 Electricity and CircuitsSC16 Earth and Space
→
Next Lesson: SC7 Plants and PhotosynthesisPlants make their own food.
📄 Free printable: Download the The Circulatory System cheat sheet (PDF) — keep it by your child's desk.

Quick summary

Frequently asked questions

What does the circulatory system do?

It transports oxygen, nutrients and waste around the body. The heart pumps blood to the lungs for oxygen, then out to every cell.

Does the heart make oxygen?

No — the lungs collect oxygen from the air we breathe, and it passes into the blood. The heart pumps that oxygen-rich blood around the body.

Why does the heart beat faster during exercise?

Working muscles need more oxygen, so the heart pumps faster (and breathing quickens) to deliver it more quickly.

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