The heart has four valves that control the flow of blood. Two of the valves (the AV valves) normally prevent blood fromflowing upwards. The other two valves (semilunar valves) normally prevent blood from flowing downwards. The AV valvesand semilunar valves have different shapes. Which principle of anatomy and physiology does this example represent?
1. Organ systems are interconnected.
2. Organ systems contribute to homeostasis.
3. There is a hierarchy of anatomical organization in an organism.
4. Structure is linked to function.