Editing Heart (section)

====Heart sounds====
[[File:Apikal4D.gif|thumb|[[Echocardiography#Three-dimensional echocardiography|3D echocardiogram]] showing the mitral valve (right), tricuspid and mitral valves (top left) and aortic valve (top right).<br /> The closure of the heart valves causes the [[heart sounds]].]]
{{listen|filename=HROgg.ogg|title=Normal heart sounds|description=Normal heart sounds as heard with a [[stethoscope]]|format=[[Ogg]]}}
Typically, healthy hearts have only two audible [[heart sounds]], called S1 and S2. The [[first heart sound]] S1, is the sound created by the closing of the atrioventricular valves during ventricular contraction and is normally described as "lub". The [[second heart sound]], S2, is the sound of the semilunar valves closing during ventricular diastole and is described as "dub".<ref name="CNX2014"/> Each sound consists of two components, reflecting the slight difference in time as the two valves close.<ref name="TC2014">{{cite book|title=Clinical Examination|last1=Talley|first1=Nicholas J.|last2=O'Connor|first2=Simon|publisher=Churchill Livingstone|isbn=978-0-7295-4198-5|pages=76–82|year=2013}}</ref> S2 may [[split S2|split]] into two distinct sounds, either as a result of inspiration or different valvular or cardiac problems.<ref name=TC2014/> Additional heart sounds may also be present and these give rise to [[gallop rhythm]]s. A [[third heart sound]], S3 usually indicates an increase in ventricular blood volume. A [[fourth heart sound]] S4 is referred to as an atrial gallop and is produced by the sound of blood being forced into a stiff ventricle. The combined presence of S3 and S4 give a quadruple gallop.<ref name="CNX2014"/>
[[Heart murmur]]s are abnormal heart sounds which can be either related to disease or benign, and there are several kinds.{{sfn|Davidson's|2010|pp=556–559}} There are normally two heart sounds, and abnormal heart sounds can either be extra sounds, or "murmurs" related to the flow of blood between the sounds. Murmurs are graded by volume, from 1 (the quietest), to 6 (the loudest), and evaluated by their relationship to the heart sounds, position in the cardiac cycle, and additional features such as their radiation to other sites, changes with a person's position, the frequency of the sound as determined by the side of the [[stethoscope]] by which they are heard, and site at which they are heard loudest.{{sfn|Davidson's|2010|pp=556–559}} Murmurs may be caused by [[Valvular heart disease|damaged heart valves]] or congenital heart disease such as [[ventricular septal defect]]s, or may be heard in normal hearts. A different type of sound, a [[pericardial friction rub]] can be heard in cases of pericarditis where the inflamed membranes can rub together.