What is atrial septal defect? Why is this condition damaging? Why are ventricular walls thicker than atrial walls? Compare and contrast the human heart versus the sheep heart

                                                                                                                                                                                                        What is atrial septal defect? Why is this condition damaging?

1. Why are ventricular walls thicker than atrial walls?
2. Compare and contrast the human heart versus the sheep heart.
3. What is the purpose of auscultating at all four heart areas?
4. What cardiac event causes the first heart sound (S1; "lubb")? What cardiac event causes the second heart sound (S2;"dupp")?