Question

the sound lub is produced in the heart when

Answer 1

ahoy.

when both the ventricles contract the two auriculo-ventricular valves ( right tricupid and mitral valve ) close producing lub sound.

peace.

Answer 2

The lub is the sound of the tricuspid and mitral values closing. The dub is the sound of the aortic and pulmonary valves closing.The sound of the heart lub-dub comes from the closer of two pairs of heart valves.