question_answer 52)

    What prevents backflow of blood inside the heart during contraction? (a) Valves in heart                  (b) Thick muscular walls of ventricles (c) Thin walls of atria       (d) All of these

Answer:

                  (a) Valves ensure that blood does not flow backwards when the atria or ventricles contract. Since ventricles have to pump blood into various organs with high pressure, they have thicker walls than atria. The separation of the right side and left side of heart by value also helps to keep oxygenated and deoxygenated blood from mixing so as to supply high amount of oxygen to the body.