Final answer:
The S1 sound ('lub') is due to the closure of atrioventricular valves, whereas the S2 sound ('dub') is due to the closure of the semilunar valves. A heart murmur is an abnormal sound indicating turbulent blood flow within the heart, which can be graded according to its severity.
Step-by-step explanation:
What Valves Cause the S1 and S2 Heart Sounds?
The S1 heart sound is produced by the closing of the atrioventricular (AV) valves, which include the mitral and tricuspid valves. This occurs during ventricular contraction and is characterized by the "lub" sound. The S2 heart sound, described as a "dub," follows the closure of the semilunar valves, which are the aortic and pulmonary valves, during ventricular diastole.
What is a Heart Murmur?
A heart murmur is described as an unusual heart sound caused by turbulent blood flow, often detected by a stethoscope. Murmurs vary in severity, graded on a scale of 1 to 6, with a grade 1 murmur being the least serious and a grade 6 being the most severe. Conditions such as valve abnormalities can result in heart murmurs, and they may be a sign of underlying heart issues.