Question

The diagram given below represents a section of the human heart.
What causes the heart sounds 'LUBB' and 'DUP'?

Answer 1

The “ lub” is the first heart sound which is caused due to the closure of mitral and tricuspid valves at the start of systole. The ”dub” is the second heart sound caused due to the closure of aortic and pulmonic valves at the end of systole.