Which structure has thicker walls: atria or ventricles?

The ventricles have thicker walls compared to the atria, primarily due to their roles in the circulatory system. The ventricles are responsible for pumping blood out of the heart: the left ventricle pumps oxygenated blood to the entire body, while the right ventricle sends deoxygenated blood to the lungs. This requires a significant amount of force to overcome the pressure in the systemic circulation (for the left ventricle) and the pulmonary circulation (for the right ventricle).

The thicker muscular walls of the ventricles are essential for this robust pumping action, enabling them to generate enough pressure to move blood efficiently. In contrast, the atria have thinner walls since their primary function is to receive blood returning to the heart and to push it gently into the ventricles. They do not need to exert the same level of force, which is why their walls are comparatively thinner.

This anatomical difference highlights the functional adaptations of the heart's chambers according to their specific roles in circulation.