Description: Segment 1 An experiment is carried out to show the workings of the mitral valve in the heart. The intertitles describe the equipment needed to perform the experiment. An animation is used to show what happens in the experiment. A funnel is connected to a tube, which is connected to a heart ventricle. Liquid is poured into the funnel and it passes into the tube and then into the ventricle. The mitral valve is open at this time. When water fills the ventricle, the mitral valve closes due to internal pressure. A second tube acts as a siphon, suctioning liquid out of the ventricle. The mitral valve opens due to outer, atmospheric pressure. This equalises the pressure and the valve closes. The intertitles note that this process repeats indefinitely. The same experiment is carried out on a sheep's heart. A doctor indicates the flow of the liquid into the heart. The valve is shown in action. A segment of the valve is removed, and this prevents it from keeping the liquid in the ventricle. Liquid is shown coming through the damaged valve. Time start: 00:00:00:00 Time end: 00:05:48:24 Length: 00:05:48:24