Question

why are the walls of ventricle more muscular than the walls of atria

Answer 1

Hello @tannurawat !
Welcome to OS

Answer 2

Ventricles have thicker walls than atria and generate higher blood pressures. The physiologic load on the ventricles requiring pumping of blood throughout the body and lungs is much greater than the pressure generated by the atria to fill the ventricles. Further, the left ventricle has thicker walls than the right because it needs to pump blood to most of the body while the right ventricle fills only the lungs.