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This animation will show how the heart works.
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Your heart is a muscular organ which lies in the centre of your chest.
It pumps blood containing oxygen
from the lungs to the body,
and passes blood without oxygen back to the lungs to absorb more oxygen.
To do this effectively, your heart is divided into four compartments
(chambers).
There are two chambers on the right side of the heart and two on the left.
A valve lies at the exit of each chamber.
The valves ensure that blood flows in one direction only.
The left atrium lies above the left ventricle.
The two are separated by a valve called the mitral valve.
The right atrium is above the right ventricle.
These two chambers are separated by the tricuspid valve.
The left atrium receives blood that contains oxygen from the lungs via the
pulmonary veins.
This blood then passes into the left ventricle,
which pumps it into the aorta.
From the aorta the blood is passed to the different parts
of the body.
The right atrium receives blood with little oxygen from the body via
the vena cava.
This blood passes into the right ventricle,
which pumps it into the pulmonary artery and back to the lungs to have oxygen
added to it.
The valve at the exit of the left ventricle (the aortic valve) stops blood passing back
into the ventricle.
The pulmonary valve at the exit of the right ventricle also stops blood
flowing backwards.
This flow of blood doesn't happen automatically.
It's driven by contractions of the heart muscle which are triggered by electrical
impulses.
A pacemaker in the upper part of the right atrium called the sinoatrial node
sends electrical impulses across the atria that cause them to contract.
The impulses reach the atrioventricular node, which is between the right atrium
and ventricle,
and pass on to the atrioventricular bundle, causing
the ventricles to contract and send blood to the lungs and around
the body.
These electrical impulses spread across the heart muscle to ensure it contracts
in the correct sequence.
Nerves supplying the heart change the rate at which impulses are sent across
the heart muscle to meet the needs of the body.
Together the chambers, valves, vessels and
electrical impulses enable blood to be pumped around the body effectively
so you get the oxygen you need.
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