The aortic valve is semilunar (half-moon shaped) with three cusps. It separates the heart from the aorta. Each cusp is attached to the aortic wall creating a sinus; a Valsalva sinus. The origins of the two coronary arteries are sited in two Valsalva sinuses, each named after the coronary artery they supply. Leaflets are separated by commissures. The posterior leaflet is in continuation with the anterior leaflet of the mitral valve (the tissue is called the aorto-mitral curtain). The aortic valve is opened during systole, the driving force for it to open is the difference in pressure between the contracting left ventricle of the heart and the aorta. During cardiac diastole (when the heart chamber gets bigger) the aortic valve closes.
