This dissected heart shows the left ventricle and the muscular wall of the septum. The left side of the heart is much more muscular than the right side of the heart, which is why we seem to feel our heartbeat more on the left side of the chest. The valve that separates the left atrium and the left ventricle is the bicuspid, also known as the atrioventricular valve. It is shown on the photo as the white flap attached by strings, the chordae tendinae (heart strings). The papillary muscles then anchor the valve in place.