THE HEART SOUNDS

Lub-dub, lub-dub   type   of   sound   heard   with   a stethoscope placed over chest in heart's postion is called heart sound.Lub = First heart sound Dub = Second heart sound.

Production of Heart Sounds

Heart sounds are produced by closure of valves(not by opening of valves).Closure of valves sets up vibrations in valves, in adjacent blood, in walls of  heart and in major vessels around heart.These vibrations are heard as heart sounds.

Kinds of Heart Sounds:

    First Heart Sound (Lub)

     Occurs at beginning of systole. Produced due to closure of AV valves. (0.14 sec).

    Second Heart Sound (Dub)

    Occurs at end of systole. Produced due to closure of semilunar (aortic and pulmonary) valves.(O.11 sec)

   Third Heart Sound

  Occurs at begining of middle third-of diastole.Produced by oscillation of blood back and forth b/w walls of ventricles initiated by inrushing blood from atria.

 Fourth Heart Sound or Atrial Sound

 Occurs when atria contract. Produced by inrush of blood into ventricles.Valves on the night side of heart open first but close last. A delayed closing of the pulmonary valves, as occurs during inspiration, can cause splitting of the second heart sound.

  • Congetial Heart defects (ASD,VSD,PDA and TOF).
  • Valvular Heart diseases(MS,MR,AS,AR).

After the end of the lesson students will be able to learn about​:

  • The Heart sounds.
  • The Heart Murmers.
  • The Abnormal Circulatory dynamics associated with congetial cardiac defects.
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