An S3 heart sound occurs early in diastole as the mitral and tricuspid valves open and blood rushes into the ventricles. To distinguish an S3 from a physiologic S2 split, a split S2 occurs during inspiration and S3 remains constant during the respiratory cycle. Its pitch is softer and best heard with the bell at the apex and it is one of the first clinical findings in left ventricular failure. An S4 is heard in late diastole when atrial contraction pumps volume into a stiff, noncompliant ventricle. An S4 is not heard in a client with atrial fibrillation because there is no atrial contraction. Murmurs are sounds created by turbulent blood flow through an incompetent or stenotic valve. CN: Physiological adaptation;
Our drinking water comes from lakes, rivers and groundwater. For most Americans, the water then flows from intake points to a treatment plant, a storage tank, and then to our houses through various pipe systems.
