ANTONIA REEVE / SCIENCE PHOTO LIBRARY ANTONIA REEVE / SCIENCE PHOTO LIBRARY
Heart surgery. Artificial heart valve held above its site of attachment. The valve has been sewn onto the heart by its soft fabric valve ring and its thread is ready to be pulled tight. The four heart valves prevent blood from re-entering each of the heart chambers once it has been pumped out. If one of these valves becomes narrowed or leaky, due to damage or disease for example, it must be replaced with a prosthetic valve.
Model release not required. Property release not required.