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first heart sound

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n.

The heart sound that occurs with ventricular systole and is produced mainly by closure of the atrioventricular valves.

QUIZZES

QUIZ YOURSELF ON “THEIR,” “THERE,” AND “THEY’RE”

Are you aware how often people swap around “their,” “there,” and “they’re”? Prove you have more than a fair grasp over these commonly confused words.
Question 1 of 7
Which one of these commonly confused words can act as an adverb or a pronoun?
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

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