Which heart sound is associated with the closure of the mitral and tricuspid valves?

The heart sound associated with the closure of the mitral and tricuspid valves is the first heart sound, known as S1. This sound marks the beginning of ventricular systole and occurs immediately after the ventricles fill with blood during diastole. When the ventricles contract, the pressure in them rises, causing the mitral and tricuspid valves to close to prevent backflow of blood into the atria. The sudden closure of these valves produces the distinctive sound heard during a cardiac examination.

In contrast, S2 is associated with the closure of the aortic and pulmonic valves and occurs at the end of ventricular systole. S3 is often related to rapid ventricular filling, usually occurring during early diastole, and is sometimes a sign of heart failure. S4, on the other hand, occurs just before S1 and is associated with atrial contraction, often indicating stiffness of the ventricle or increased resistance to filling. Thus, S1 is specifically linked to the closure of the mitral and tricuspid valves, clearly defining it as the correct answer.