Library · Physiology
Where the heart sounds come from
Make it clearer
What you hear when you put a stethoscope on the chest is blood passing through the chambers of the heart while the valves open and close. That flow sets the structures of the heart vibrating, and that vibration is the sound.
The first sound, called S1 in medicine, is produced by two valves closing at the same time: the mitral and the tricuspid, the ones that separate each atrium from its ventricle. They close in systole, the moment when the heart contracts to push blood out. Of the two, the mitral is the one that sounds louder.
The second sound, S2, comes from the other two: the aortic and the pulmonary, the outflow valves. They close in diastole, which is when the heart relaxes and fills again. The aortic closes before the pulmonary and sounds louder, and the reason is pressure: it is higher in the aorta than in the pulmonary artery.
In brief
Heart sounds come from blood moving through the heart's chambers as the valves open and close: what you hear is those structures vibrating.
The first, S1, is produced by closure of the mitral and tricuspid valves in systole; the mitral is its louder component.
The second, S2, is produced by closure of the aortic and pulmonary valves in diastole; the aortic closes first and sounds louder because pressure in the aorta is higher.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Heart Sounds, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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