What do human heart valves look like?

Human heart valves are muscular structures, as seen in the cross section provided by YourHeartValve.com. The mitral and tricuspid valves are wider and open with a rounder shape, while the aortic and pulmonary valves are thinner and open with a triangle-like shape.

The valves, made of strong muscle fiber, act as doors to the four chambers of the heart, allowing or preventing the flow of blood into and throughout the heart, as described by the American Heart Association. Certain infections cause the muscles of the valves to become inflamed and swollen, which can affect their ability to function properly, as WebMD describes.