The ventricle has thicker, more muscular walls than the atria. relate this difference in wall structure to the 2 types of heart chamber.

The atria are the heart chambers which receive blood from other organs into the heart. The structure of the atria is determined by the type of function which they performed. Atria are thin walled with no inlet valve and their contraction is gentle and incomplete. Thus, the walls of the atria are thin because they are not involve in blood pumping. The ventricle on the other hand has thick, muscular wall because it has to pump blood out of the heart through strong contractions and it thus generate higher blood pressure. The left ventricle is even thicker than the right ventricle because it has to pump blood out to the greater parts of the body while the right ventricle only pump out blood to the lungs.

All of them are man made