In which part of the heart would you find thinner walls?

The atria of the heart have thinner walls compared to the ventricles. This anatomical difference is primarily due to the varying roles that these chambers play in the cardiac cycle. The atria are responsible for receiving blood from the body (the right atrium) and the lungs (the left atrium) and pushing it down into the ventricles. This function does not require as much muscular strength, allowing the walls to be thinner.

In contrast, the ventricles must generate significantly higher pressure to pump blood out of the heart and into the lungs (the right ventricle) and the rest of the body (the left ventricle). Consequently, their walls are much thicker, particularly the left ventricle, which needs to exert a substantial amount of force to overcome systemic vascular resistance.

The other options, such as arteries and veins, refer to blood vessels rather than heart chambers. Arteries typically have thick, muscular walls to withstand and maintain high-pressure blood flow from the heart, while veins have thinner walls than arteries but are still designed to sustain lower pressure and have a different structural composition to accommodate the volume of blood returning to the heart. Therefore, the atria are identified as having thinner walls when examining the heart's structure.