Heart Sounds – Cardiac Cycle

by Thad Wilson, PhD

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    So far, we’ve really only talked about blood pressure and volume. Now, we’re going to introduce another concept that’s really important for you clinically. You know this inherently in the inherent lub-dub sound of the heart. You can put a stethoscope on someone's chest and listen to heart sounds. This is one of your clinical items that you can try to make sure that you’re understanding how the heart is functioning. So, let's go through what are the heart sounds that you can hear. The first one is known as S1. This involves when the mitral, which is the bicuspid, and the tricuspid valves close. They close about at the same time. This is around the same time as the QRS complex and it's during isovolumic contraction. There's a little bit of a split sound, in that the bicuspid valve, which is also known as the mitral, precedes the tricuspid valve closing just by a very short timeframe. The next sound that you hear is when the aortic and the pulmonary valves close. This occurs along the ECG just after the T wave and is about at the same time as isovolumic relaxation. This gives you two insights. You can think of isovolumic contraction and isovolumic relaxation as being times when you hear S1 and S2. This happens when those valves close. The aortic valve precedes the pulmonary valve closing by just a split second. This allows for there to sometimes be a split sound in the stethoscope listening of those sounds. So, you might hear two different S2 sounds. Now, why are these sounds important? Well, if you think about having the mitral valve and tricuspid valves close, if a person has a murmur in these two valves, you can hear it around S1. If there is a murmur...

    About the Lecture

    The lecture Heart Sounds – Cardiac Cycle by Thad Wilson, PhD is from the course Cardiac Physiology.

    Included Quiz Questions

    1. S3
    2. S1
    3. S2
    4. S4
    1. Closure of aortic and the pulmonary valves
    2. Flow of blood from atria
    3. Contraction of atria
    4. Closure of AV valves
    5. Contraction of ventricles
    1. Closure of AV valves
    2. Closure of semilunar valves
    3. Contraction of ventricles
    4. Flow of blood from atria
    5. Contraction of atria

    Author of lecture Heart Sounds – Cardiac Cycle

     Thad Wilson, PhD

    Thad Wilson, PhD

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