A<unk>  is a one-way<unk>  that allows blood to flow in one direction through the chambers of the heart. Four<unk> s are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A<unk>  opens or closes according to differential blood pressure on each side. The four<unk> s in the mammalian heart are two atrioventricular<unk> s separating the upper atria from the lower ventricles – the mitral<unk>  in the left heart, and the tricuspid<unk>  in the right heart. The other two<unk> s are at the entrance to the arteries leaving the heart these are the semilunar<unk> s – the aortic<unk>  at the aorta, and the pulmonary<unk>  at the pulmonary artery. The heart also has a coronary sinus<unk> , and an inferior vena cava<unk> , not discussed here.
Heart valve
Coronary circulation
Endobronchial valve
Pericardial heart valves
Electrical conduction system of the heart
Cranial nerves
Soft tissue
Cardiac cycle