Medical professionals call this a murmur. Rheumatic fever is a disease that can damage the heart valves. Accumulated fat deposits in the heart can also affect the function of the valves. If the valves become too small or leaky due to either of these conditions, they can be surgically replaced with artificial valves. The heart contains valves which direct the flow of blood in one direction.
Blood is forced through the flexible membranes which form the valves.
Once the blood passes through the membranes, the valves collapse into a barrier, preventing the blood from flowing backwards. Likewise, the balloon pump and the bike pump force air into a chamber. After explaining open and closed systems, ask for examples of open and closed systems. An example of an open system is household plumbing. Examples of closed systems include the refrigeration units of refrigerators and hot water heating systems in houses.