How does blood enter the ventricles from the atria?

Blood enters the ventricles from the atria through the atrioventricular (AV) valves. When the atria contract, they push blood through the open AV valves into the ventricles. The right atrium sends deoxygenated blood to the right ventricle via the tricuspid valve, while the left atrium sends oxygenated blood to the left ventricle through the mitral valve. The valves close after the ventricles fill to prevent backflow during ventricular contraction.