Question

Why is the wall of the atrium thin? Why is the left ventricle wall thicker and more muscular than the right ventricle wall?

Answer 1

left ventricle need to has a powerful contraction forcfe to force the blood flow thorught most part of our body, hence it need to has thick mucsle. Right ventricle only pump the blood to the lung, shorter distance, hence don have powerful muscle like left ventricle.

Answer 2

With regards to the right atrium, the distance is less of an issue than the fact that the lung can't handle high pressures in its capillaries.