This apical view offers a symmetric display of the two large atrio-ventricular valves appearing to lie horizontally on the screen along the plane of the atrio-ventricular groove. By convention the left ventricle is displayed to the viewer's right. The interventricular septum and interatrial septum form what is seen as the verticle column of tissue in the middle of the image. The interventricular septum tends to contract toward the left ventricular cavity during systole because of the higher pressure requirements of that chamber. A "five" chamber view involves tilting the image plane superiorly to show the base of the aortic valve and the left ventricular outflow tract.