Final answer:
The right atrioventricular valve, also known as the tricuspid valve, prevents the backflow of blood from the right ventricle into the right atrium.
Step-by-step explanation:
The valve that prevents the backflow of blood from the right ventricle into the right atrium is the right atrioventricular valve (tricuspid valve). This valve operates as a one-way gateway, allowing blood to flow from the right atrium to the right ventricle and preventing it from flowing back into the atrium. When the right ventricle contracts, the tricuspid valve closes, ensuring that blood is pushed forward into the pulmonary arteries through the pulmonary valve, rather than back into the right atrium.