The two atria are separated from the ventricles by membranous valves. The valve separating the right auricle from the right ventricle is known as the right atrioventricular valve or tricuspid valve (as it is made of three flaps or cusps). The valve separating the left atrium and the left ventricle is called left atrioventricular valve or the bicuspid valve or the mitral valve (since it is made of two flaps).