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School Learning Zone - The Circulatory System

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Learn about the circulatory system with this Year 6 Bitesize Science guide.

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It's a muscle, about the size of your fist, in the middle of your chest tilted slightly to the left.

What is the function of the human heart?

Each day, your heart beats around 100,000 times. This continuously pumps about five litres (eight pints) of blood around your body through a network of blood vessels called your circulatory system. This blood delivers oxygen and nutrients to all parts of your body to help your organs and muscles work properly. Your blood also carries away unwanted carbon dioxide and waste products.

What is the structure of the human heart?

Your heart has a left side and a right side, they are separated by a thin muscular wall called the Septum. Both sides of your heart have an upper chamber and a lower chamber.

the upper chambers are called the left atrium and the right atrium (or the atria)

the lower chambers are called the left ventricle and the right ventricle.

The right side of your heart receives the de-oxygenated blood that has just travelled round your body. It pumps the blood to your lungs to collect a fresh supply of oxygen. The left side of your heart pumps the re-oxygenated blood round your body again.

Your heart muscle is made up of three layers of tissue:

Pericardium - a thin, outer lining that protects and surrounds your heart.

Myocardium - a thick, muscular middle layer that contracts and relaxes to pump blood around of your heart.

Endocardium - a thin, inner layer that makes up the lining of the four chambers and the valves in your heart.

What does the heart's electrical system do?

Your heart's electrical system tells your heart when to contract and when to relax to keep your blood pumping regularly. The instructions to contract and relax are carried by electrical signals.

The electrical signals are sent from the sinus node which is known as your heart's natural pacemaker. Usually, the sinus node will send the electrical signals at a steady pace, but the pace can change depending on your emotions and if you are active or resting - this is your heart rate.

How does blood flow around the heart and the body?

Your heart is linked to the rest of the circulatory system with blood vessels called arteries and veins.

your arteries deliver oxygen-rich blood from the heart to other areas of your body

your veins return the de-oxygenated blood from your organs back to your heart

your arteries and veins are connected by even smaller blood vessels called capillaries.

Your blood flows around your heart and the rest of your body in one direction, like a one-way traffic system. Your heart valves control the direction of your blood flow, they act like doors that open and close with every heartbeat. There are four valves in your heart, they are:

the tricuspid valve and the pulmonary valve on the right side of the heart

the mitral valve and the aortic valve on the left side of your heart.

Like the rest of your body, your heart needs to be supplied with oxygen-rich blood to work properly too. The coronary arteries are the arteries responsible for supplying the heart with oxygenated blood. The coronary arteries are spread across the outside of the heart to deliver the blood.

How do your heart and lungs add oxygen to your blood?

Your blood flows through your heart and your lungs to become re-oxygenated before being pumped to the rest of your body. Oxygen is added to your blood in four main steps, they are:

The right atrium receives the low-oxygen blood that has just travelled round the body. The right atrium pumps the blood to the right ventricle.

The right ventricle pumps the low-oxygen blood to the lungs to pick up a fresh supply of oxygen.

The left atrium receives to high-oxygen blood from the lungs and pumps it to the left ventricle.

The left ventricle pumps the high-oxygen blood to the rest of the body.

What are heart and circulatory diseases?

Sometimes the heart and circulatory system don't work like they should, this can cause heart and circulatory diseases (also called cardiovascular diseases). We fund research into these conditions and their risk factors, including:

What causes your heart and circulatory system to go wrong?

Problems with your heart and circulatory system, including heart attack or a stroke, are usually caused by a gradual build-up of fatty material (called atheroma) in the arteries around the heart and in the arteries that supply blood to your brain.

The fatty material lines the walls of heart's coronary arteries making the space for blood to flow narrower. When the arteries become narrowed and the blood flow is restricted, the arteries can't deliver enough blood to the heart and the brain, which can cause heart and circulatory diseases.

What puts me at risk of heart and circulatory disease?

Many heart and circulatory diseases share the same risk factors including:

Heart and circulatory diseases can be worrying but the good news is that there are lots of things you can do to reduce your risk of developing heart and circulatory diseases now.

Check your heart age

You can trust our health information

We've followed an eight-step process to make sure this content is reliable, accurate and trustworthy. Learn how we make our health information reliable and easy to understand.
Page last reviewed: August 2021
Next review due: August 2024
Support our life saving research

We're funding vital research to help prevent and treat people living with heart and circulatory diseases. But more needs to be done.
DONATE
Your support funds crucial research so that we can beat these conditions and save lives.

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Find out how a healthy heart works and its role pumping blood around your body. Watch our short animated guide to your heart.

# data[].attributes.attachment_link.readable_text
It's a muscle, about the size of your fist, in the middle of your chest tilted slightly to the left.

What is the function of the human heart?

Each day, your heart beats around 100,000 times. This continuously pumps about five litres (eight pints) of blood around your body through a network of blood vessels called your circulatory system. This blood delivers oxygen and nutrients to all parts of your body to help your organs and muscles work properly. Your blood also carries away unwanted carbon dioxide and waste products.

What is the structure of the human heart?

Your heart has a left side and a right side, they are separated by a thin muscular wall called the Septum. Both sides of your heart have an upper chamber and a lower chamber.

the upper chambers are called the left atrium and the right atrium (or the atria)

the lower chambers are called the left ventricle and the right ventricle.

The right side of your heart receives the de-oxygenated blood that has just travelled round your body. It pumps the blood to your lungs to collect a fresh supply of oxygen. The left side of your heart pumps the re-oxygenated blood round your body again.

Your heart muscle is made up of three layers of tissue:

Pericardium - a thin, outer lining that protects and surrounds your heart.

Myocardium - a thick, muscular middle layer that contracts and relaxes to pump blood around of your heart.

Endocardium - a thin, inner layer that makes up the lining of the four chambers and the valves in your heart.

What does the heart's electrical system do?

Your heart's electrical system tells your heart when to contract and when to relax to keep your blood pumping regularly. The instructions to contract and relax are carried by electrical signals.

The electrical signals are sent from the sinus node which is known as your heart's natural pacemaker. Usually, the sinus node will send the electrical signals at a steady pace, but the pace can change depending on your emotions and if you are active or resting - this is your heart rate.

How does blood flow around the heart and the body?

Your heart is linked to the rest of the circulatory system with blood vessels called arteries and veins.

your arteries deliver oxygen-rich blood from the heart to other areas of your body

your veins return the de-oxygenated blood from your organs back to your heart

your arteries and veins are connected by even smaller blood vessels called capillaries.

Your blood flows around your heart and the rest of your body in one direction, like a one-way traffic system. Your heart valves control the direction of your blood flow, they act like doors that open and close with every heartbeat. There are four valves in your heart, they are:

the tricuspid valve and the pulmonary valve on the right side of the heart

the mitral valve and the aortic valve on the left side of your heart.

Like the rest of your body, your heart needs to be supplied with oxygen-rich blood to work properly too. The coronary arteries are the arteries responsible for supplying the heart with oxygenated blood. The coronary arteries are spread across the outside of the heart to deliver the blood.

How do your heart and lungs add oxygen to your blood?

Your blood flows through your heart and your lungs to become re-oxygenated before being pumped to the rest of your body. Oxygen is added to your blood in four main steps, they are:

The right atrium receives the low-oxygen blood that has just travelled round the body. The right atrium pumps the blood to the right ventricle.

The right ventricle pumps the low-oxygen blood to the lungs to pick up a fresh supply of oxygen.

The left atrium receives to high-oxygen blood from the lungs and pumps it to the left ventricle.

The left ventricle pumps the high-oxygen blood to the rest of the body.

What are heart and circulatory diseases?

Sometimes the heart and circulatory system don't work like they should, this can cause heart and circulatory diseases (also called cardiovascular diseases). We fund research into these conditions and their risk factors, including:

What causes your heart and circulatory system to go wrong?

Problems with your heart and circulatory system, including heart attack or a stroke, are usually caused by a gradual build-up of fatty material (called atheroma) in the arteries around the heart and in the arteries that supply blood to your brain.

The fatty material lines the walls of heart's coronary arteries making the space for blood to flow narrower. When the arteries become narrowed and the blood flow is restricted, the arteries can't deliver enough blood to the heart and the brain, which can cause heart and circulatory diseases.

What puts me at risk of heart and circulatory disease?

Many heart and circulatory diseases share the same risk factors including:

Heart and circulatory diseases can be worrying but the good news is that there are lots of things you can do to reduce your risk of developing heart and circulatory diseases now.

Check your heart age

You can trust our health information

We've followed an eight-step process to make sure this content is reliable, accurate and trustworthy. Learn how we make our health information reliable and easy to understand.
Page last reviewed: August 2021
Next review due: August 2024
Support our life saving research

We're funding vital research to help prevent and treat people living with heart and circulatory diseases. But more needs to be done.
DONATE
Your support funds crucial research so that we can beat these conditions and save lives.

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Find out how a healthy heart works and its role pumping blood around your body. Watch our short animated guide to your heart.

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Circulatory System for Kids | Learn all about how blood travels through the body

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Your heart is a very strong muscle which contracts (gets smaller) and relaxes to pump blood around your body. A heart beat varies from person to person - for an average person it beats 60-100 times a minute. You feel this when you feel your

This is the journey that blood takes:

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Learn about the circulatory system with this Year 6 Bitesize Science guide.