The opening between the right atrium and the right ventricle is guarded by __________.

Step-by-step solution

The opening between the right atrium and the right ventricle is guarded by a valve formed of three muscular flaps or cusps, known as the tricuspid valve. The bicuspid or mitral valve guards the opening between the left atrium and the left ventricle. The semilunar valves guard the openings of the right and left ventricles into the pulmonary artery and the aorta, respectively. The sino-atrial node is a specialized cardiac musculature present in the right upper corner of the right atrium.