Expert: John Locke - 1/14/2007

Question
We saw a sign at the Bodies exhibit that said that each drop of blood in an adult human goes through the heart every minute. Is this true? How long does it take for the entire volume of blood in an average adult human to be pumped through the heart?

Answer
Thanks for using AllExperts, John. The answer to your question is yes; at rest, the heart pumps at such a rate that the blood completes one circuit around the body in one minute (for a person weighing between 130-170 pounds, roughly). That's not the end of it, however: how much blood you have depends on body weight, and how much blood you have (in part) determines how often the blood circulates in the body. Let me lay this out specifically:

The rate at which a person's blood circulates through their body is measured by the cardiac output, which is the product of the heart rate (how many times the heart beats in one minute) and the stroke volume (how much blood the heart pumps in one beat). When you take the average values for an adult at rest, the cardiac output comes out to about 5 liters/min; given that a person who weighs 160 pounds has about 5 liters of blood in their body, we can see that all the blood completes one circuit in one minute. People who weigh much less will have their blood complete more than one circuit in a minute, and people who weigh much more will take more time (but not a lot more time: people who weigh more will tend to have a higher stroke volume and/or heart rate, as well). Exercise can raise the cardiac output dramatically, up to 30 liters/minute for very heavy exercise.

To put it simply, yes, the exhibit you saw got it right--for an average person, at rest.