What causes the opening of heart valves?

The opening of heart valves is primarily caused by the difference in pressure between the chambers of the heart and the corresponding blood vessels. Here's a more detailed explanation:

1. Atrioventricular (AV) valves: The AV valves, which include the mitral valve (left side of the heart) and the tricuspid valve (right side), separate the atria (upper chambers) from the ventricles (lower chambers) of the heart. These valves open when the pressure in the atria exceeds the pressure in the ventricles.

- During atrial systole (contraction), the pressure in the atria increases. As a result, the AV valves are forced open, allowing blood to flow into the ventricles.

2. Semilunar valves: The semilunar valves, which include the aortic valve and the pulmonary valve, control blood flow from the ventricles to the arteries (aorta and pulmonary artery, respectively). These valves open when the pressure in the ventricles exceeds the pressure in the arteries.

- During ventricular systole (contraction), the pressure in the ventricles increases significantly. This pressure difference causes the semilunar valves to open, allowing blood to be pumped out of the heart and into the circulation.

The opening and closing of heart valves are crucial for maintaining proper blood circulation. They ensure that blood flows in the correct direction and prevents backflow. This coordinated valvular action is regulated by the electrical conduction system of the heart and the interplay of cardiac muscle contractions and pressure changes within the heart chambers.