Description: Segment 1 A dog has been prepared for surgery and is anaesthetised. An incision is made and the dog's heart is exposed. The narrator points out parts of the heart. An animated illustration shows the circulation of blood in the heart, and its anatomy. The dog's heart is attached to a mechanical heart. This is also described with an animated illustration. A tourniquet is used to prevent the blood of blood to the right lung and the effects observed. The tourniquet is released and another tourniquet is tightened around the right pulmonary artery and the effects observed. Time start: 00:00:00:00 Time end: 00:05:59:04 Length: 00:05:59:04 Segment 2 The dog's left lung is shown. The mitral valve is shown. The camera changes position a number of times to show different views of the mitral valve. A post-mortem heart is used to show the anatomy of the heart more easily. Due to the lack of fluid in the heart (made possible by the mechanical heart), the movements of the mitral valve are easily observed. Various views of the mitral and aortic valves are shown. Time start: 00:05:59:04 Time end: 00:12:34:23 Length: 00:06:35:19