Physiology The first heart sound is produced by the: A Closure of the aortic and pulmonary valves B Opening of the aortic and pulmonary valves C Closure of the mitral and tricuspid valves D Opening of the mitral and tricuspid valves 💡 Explanation The first heart sound is produced by the: ✓ Correct Answer: C. Closure of the mitral and tricuspid valves