What valve lies between the right atrium and right ventricle?

The valve between the right atrium and right ventricle is the tricuspid valve.

It is also called the right atrioventricular valve. During diastole, when the heart relaxes, the valve opens so blood can move from the right atrium into the right ventricle. During systole, when the ventricle contracts, it closes to prevent blood from flowing backward into the atrium.

The valve usually has three leaflets, or cusps: anterior, posterior, and septal. Thin tendinous cords called chordae tendineae connect the leaflets to papillary muscles inside the right ventricle. These structures help keep the valve from inverting when pressure rises during contraction. Despite its name, the tricuspid valve can occasionally have two or four leaflets.

A frequent confusion involves the mitral valve, which occupies the corresponding position on the left side of the heart, between the left atrium and left ventricle. The pulmonary valve is farther along the route from the right ventricle to the pulmonary artery, while the aortic valve controls blood leaving the left ventricle. Tricuspid regurgitation occurs when the valve allows backward leakage during contraction.