The four valves of the heart allow blood to flow through the heart in the right direction. The valves open or close each time the heart beats. Problems with the heart valves can lead to palpitations, ...

In a healthy heart, blood flows in only one direction. The four valves of the heart prevent blood from flowing backward. But a leaky heart valve, or heart valve regurgitation, causes a backflow of ...

This schematic illustrates the organization of blood vessels and the regulation of blood flow (arrows) in the palm of the hands. Arteriole-venule shunts are small muscular valves that connect directly ...