Can you explain the different valves of the heart and why they are important?

The heart consists of 4 chamber; left and right atria, plus left and right ventricles. The right atria recieves deoxygenated blood from the superior and inferior vena cava, delivering blood from the head and neck and rest of the body respectively. After the right atria fills it contracts and pumps blood to the right ventricle. The right ventricle then contracts to force blood through the pulmonary artery, to the lungs, where the blood is oxygenated and returned to the left atria of the heart via the pulmonary vein. As the left atria fills it contracts to force blood into the left ventricle. The left ventricle thn itself contracts to pump blood through the aorta in order to deliver blood to the whole body. 

The chambers of the heart are separated by valves. The right atria and right ventricle is sepearted by a TRIcuspid valve, consisting of 3 flaps. A good way to remember this is that TRI has an R, as in Right. Whereas the left atria and ventricle are separated by the Bicuspid (or Mitral) valve, consisting of 2 flaps. These valves allow blood to flow downards from atria to ventricles relax, but close to prevent blood flowing back up to the atria when the ventricles are contracting. The ventricles are separated from the aorta and pulmonary artery via the aortic and pulmonary valves respectively, also known as the semilunar valves. These prevent blood from flowing in the wrong direction back into the heart.