Year 6 science · Key Stage 2 · Animals, including humans

Year 6 circulatory system: the heart, blood and a healthy lifestyle

In Year 6, children learn the main parts of the human circulatory system: the heart, the blood vessels and the blood. They find out how blood carries oxygen, nutrients and water around the body, and they look at how diet, exercise, drugs and lifestyle affect the way the body works. It builds on Year 3 and 4 work on the skeleton, muscles and digestive system.

The circulatory system and healthy living, explained

The circulatory system is the body’s transport network. It has three parts. The heart is a strong muscle that works as a pump, squeezing and relaxing about once a second at rest to push blood round the body. Blood vessels are the tubes that carry blood. Blood is the liquid that does the carrying. The heart sits in the middle of the chest, tilted slightly to the left, and is roughly the size of its owner’s fist.

There are three main kinds of blood vessel. Arteries carry blood away from the heart, with thick, strong walls to cope with the pressure. Veins carry blood back to the heart. Capillaries are the tiniest vessels, with very thin walls, and they reach almost every part of the body. It is in the capillaries that oxygen, water and nutrients pass out of the blood to the body’s cells, and waste such as carbon dioxide passes in. Blood goes round in a loop, and is not used up. The right side of the heart pumps blood to the lungs to pick up oxygen, and the left side pumps it to the rest of the body. Children don’t need to name the heart’s chambers.

Blood is made of several parts. Red blood cells carry oxygen from the lungs. White blood cells help to fight germs. Platelets help blood to clot when we are cut. All of these float in a pale yellow liquid called plasma, which carries water, nutrients and waste. After food is digested, the nutrients pass through the wall of the gut into the blood, which carries them to every part of the body. Water is taken in through the gut in a similar way. Oxygen comes in through the lungs. Other animals with a heart and blood, such as dogs, birds and fish, move nutrients and water around their bodies in the same basic way.

The second half of the topic is about looking after the body. Regular exercise strengthens the heart and muscles, and a balanced diet gives the body the nutrients it needs. Children are taught that drugs, including some medicines when misused, alcohol and tobacco, can harm the body, and that sleep, rest and avoiding smoking are part of a healthy lifestyle. Schools approach this calmly and factually. Some schools look at real research linking diet, exercise and health, and pupils often measure their pulse before and after exercise to see the effect.

Words your child will hear

Heart: The muscle that pumps blood around the body.
Artery: A blood vessel that carries blood away from the heart.
Vein: A blood vessel that carries blood back to the heart.
Capillary: A tiny blood vessel where oxygen and nutrients pass into the body’s cells and waste passes out.
Pulse: The beat you can feel in your wrist or neck as the heart pumps blood along the arteries.
Nutrients: Useful substances in food, such as carbohydrates, proteins, fats, vitamins and minerals, that the body needs to grow and work.
Oxygen: A gas in the air that our bodies need. It is carried round in the blood by red blood cells.

What the National Curriculum says

In Year 6, pupils should be taught to:

Identify and name the main parts of the human circulatory system, and describe the functions of the heart, blood vessels and blood
Recognise the impact of diet, exercise, drugs and lifestyle on the way their bodies function
Describe the ways in which nutrients and water are transported within animals, including humans

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: how does exercise change your pulse?

How does exercise affect the number of times the heart beats in a minute?

Predict and explain. “I think my pulse will go up after exercise, because my muscles will need more oxygen and the heart has to pump faster to deliver it.”
Learn to find a pulse. Rest two fingers (not the thumb, which has its own pulse) lightly on the inside of the wrist, below the thumb, until you can feel a steady beat.
Take a resting reading. Sit still for a few minutes, then count the beats for 30 seconds and double it. Example: 42 beats in 30 seconds is 84 beats per minute.
Exercise for one minute, such as star jumps or running on the spot, then count again straight away. Example: 66 beats in 30 seconds is 132 beats per minute. Then measure again after two and four minutes of rest to see how long the pulse takes to recover.
Explain the result using the circulatory system. During exercise the muscles use more oxygen and energy, so the heart pumps harder and faster to send more blood to them. A fitter heart recovers more quickly.

In this example the pulse rose from 84 to 132 beats per minute after exercise. The heart beats faster because working muscles need more oxygen and nutrients, which the blood carries. Different children get different numbers, and a fair test uses the same exercise for the same time.

Common mistakes and how to help

Thinking blood in veins is blue

Veins look blue through the skin, and diagrams colour them blue to show that blood is carrying less oxygen.

What helps: Explain that blood is always red. It is a brighter red when it carries oxygen and a darker red when it carries less. A cut vein bleeds dark red, never blue.

Believing the blood gets used up, or that it goes only one way

Children think of blood as something that leaks out or is burned like fuel.

What helps: Draw the loop: heart, lungs, heart, body, heart. Blood goes round and round, dropping off and picking up useful and waste materials as it goes.

Mixing up arteries and veins

The two words sound alike and the direction of flow is easy to forget.

What helps: Remember “arteries away”: arteries carry blood away from the heart, veins carry it back. You feel a pulse in an artery because each heartbeat sends a surge of blood along it that stretches its wall.

Thinking being healthy only means eating less or being thin

Health messages in the media often focus on weight rather than on how the body works.

What helps: Talk about what the body needs: a varied diet, regular exercise, enough sleep and drinking water. Ask how each one helps the heart, muscles or blood to do their jobs.

How to help at home

Pulse before and after. Take pulse readings at rest, after one minute of star jumps in the living room, and after resting again. Draw a simple bar chart and talk about why it changes.
Pump model. Fill a rinsed-out squeezy bottle with water and squeeze it over the sink. Each squeeze is like one heartbeat pushing blood out into the arteries, and letting go is the heart relaxing and refilling. Try squeezing about once a second for a minute to feel how hard the heart muscle works without ever stopping.
Follow the meal. Over a snack, ask your child to tell the story of how a sandwich ends up giving energy to a leg muscle, from digestion through the gut wall, blood and heart to the muscle. This covers how nutrients are carried.
Plan a healthy week. Make a simple weekly plan with active time, a mix of foods and enough sleep. Let your child decide what goes in and explain the reason for each part in terms of the body.
Safe use of medicines. Take the chance to repeat the household rule: only an adult gives out medicines, and we never take someone else’s. Ask what your child has learned at school about harmful substances.

Builds on

Year 5: Human growth and puberty

Everything in Year 6 science

Updated 20 October 2026.