the cusps of the valves of the heart are covered by
Heart valve The heart valves and the chambers are lined with endocardium. Heart valves separate the atria from the ventricles, or the ventricles from a blood vessel. Heart valves are situated around the fibrous rings of the cardiac skeleton. The valves incorporate leaflets or cusps, which are pushed open to allow blood flow and which then close together to seal and prevent backflow. The mitral valve has two cusps, whereas the others have three. There are nodules at the tips of the cusps that make the seal tighter.
Heart In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles.[4][5] Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart.[6] Fish, in contrast, have two chambers, an atrium and a ventricle, while reptiles have three chambers.[5] In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow.[3] The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.[7]