Question

ventricle have thicker walls than Atria​

Answer 1

The lower chambers are the right and left ventricles, which receive blood from the atria above. Their muscular walls are thicker than the atria because they have to pump blood out of the heart.

Answer 2

ventricles recive blood from artria , so it deals with huge pressure as well as it have to pump blood out of the heart to other organs which requires huge force for contraction thus it have thicker walls than artria