Describe7 marksChallenge
During a dissection of a mammalian heart, a student observes that the walls of the atria are much thinner than those of the ventricles, and the wall of the left ventricle is noticeably thicker than that of the right ventricle. The student also hears the characteristic 'lub-dub' sounds produced by the closing of heart valves.
Describe how the structure of the mammalian heart is adapted to its function in pumping blood. In your answer:
- explain why the walls of the atria and ventricles differ in thickness, and why the left ventricle wall is thicker than the right ventricle wall;
- describe the sequence of pressure changes in the atria, ventricles and aorta during one cardiac cycle, and explain how these pressure changes cause the opening and closing of the atrioventricular and semilunar valves;
- describe the roles of the sinoatrial node, atrioventricular node and Purkyne tissue in coordinating the heartbeat.