Heart valve called the "semilunar valves". These two arteries receive blood from the ventricles and their semilunar valves permit blood to be forced into the arteries, and prevent backflow from the arteries into the ventricles. These valves do not have chordae tendineae, and are more similar to the valves in veins than they are to the atrioventricular valves. The closure of the semilunar valves causes the second heart sound. The aortic valve, which has three cusps, lies between the left ventricle and the aorta. During ventricular systole, pressure rises in the left ventricle and when it is greater than the pressure in
Crisscross heart and right ventricle are working together to supply blood to the pulmonary artery, similarly to how the left atrium and the left ventricle work simultaneously to supply blood to the aorta. During the process of the heart contracting and releasing the right atrium and left atrium contract at the same time, while the left ventricle and right ventricle relax. In opposition, when the left atrium and right atrium are relaxed the left ventricle and right ventricle contract pushing blood to either the aorta or pulmonary artery. In an anatomically correct heart the atria are smaller than the ventricles. The ventricles