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).
The heart has four valves â the aortic, mitral, tricuspid and pulmonary valves. Like valves used in house plumbing, the heart valves open to allow fluid (blood) to be pumped forward, and they close to prevent fluid from flowing backward. Human heart valves are flaps of tissue called leaflets or cusps. Heart valve problems fall into two major categories: Stenosis â The opening of the valve is too narrow, and this interferes with the forward flow of blood. Regurgitation â The valve doesn't close properly.