Final answer:
The heart's structures responsible for regulating blood movement between chambers are valves.
Step-by-step explanation:
The heart has four chambers: two atria and two ventricles. The atria receive blood, while the ventricles pump blood out of the heart. The movement of blood from one chamber to the next is regulated by valves. These valves open and close to ensure that blood flows in one direction, preventing backflow and ensuring proper circulation. For example, the atrioventricular (AV) valves, located between the atria and ventricles, prevent blood from flowing back into the atria when the ventricles contract.