Q.

Atria are thin-walled as they deliver blood just to the ventricles. Ventricles have thicker walls than atria as they need to pump blood under higher pressure over greater distances. The wall of the left ventricle is considerably thicker and highly muscular than the wall of the right ventricle because the left ventricle must force the blood to the distance parts of the body against a much greater resistance to flow. The right ventricle pumps blood a short distance to the lungs at lower pressure, and the resistance to blood flow is small.