by The Open University
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The heart pumps blood around the body. That might seem obvious, and you might think that there must be more to it than that, but there isn't. That is all that it does. However, this is a crucially important job.
Interactive content appears here. Please visit the website to use it.Here is a simple diagram of a heart and you can see from it that the heart pumps two different blood circuits. These together make up one whole cycle or pulse.
One of the circuits comes from the body to the heart and goes to the lungs. This blood doesn't have much oxygen in it and is shown as blue in colour on the diagram. The other circuit comes from the lungs where it has picked up oxygen, this is shown as red on the diagram. It goes to the heart and then around the rest of the body. You can think of this circuit as refuelling the blood. A key point to remember is that blood picks up oxygen from the lungs and carries it to all the organs, muscles and the brain.
Figure 8 Expanded view of the heart, with two pumping systemsLong descriptionWe can think of the blood going through one big cycle, through both circuits. It picks up oxygen on one half cycle, and then carries this fuel around the body, gradually distributing its supply of oxygen in the other half cycle.
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