The US in now ranked 46th on the RWB list, in between Romania and Haiti. It was ranked 32nd in the 2013 index. The press freedom group was blunt in its explanation. It cited increased efforts to track down whistleblowers and the sources of leaks, mentioning Chelsea Manning and Edward Snowden in particular.
The heart has four valves-one for each chamber of the heart. The valves keep blood moving through the heart in the right direction. The mitral valve and tricuspid valve are located between the between the atria (upper heart chambers) and the ventricles (lower heart chambers).
Your heart has four chambers. Blood pumps through these four chambers to the rest of your body. The blood in your heart flows from chamber to chamber through four different heart valves. The valves open and close to ensure that blood flows in the proper direction. Each heart valve is made up of thin but strong flaps of tissue (also called leaflets or cusps) that open and close about 100,000 times each day.