The aortic valve has three cusps. These cusps are half moon shaped hence also called aortic semilunar valve. Each cusp has a small swelling in the center called the nodule. Dilatation of the wall of the aorta behind these cusps is called aortic sinus. When the aortic valve is open, the normal size of the orifice is 3-4 cm² in adults.
During ventricular systole, pressure rises in the left ventricle. When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to close. The closure of the aortic valve contributes the A component of the second heart sound.