<P> The pulsatile nature of blood flow creates a pulse wave that is propagated down the arterial tree, and at bifurcations reflected waves rebound to return to semilunar valves and the origin of the aorta . These return waves create the dicrotic notch displayed in the aortic pressure curve during the cardiac cycle as these reflected waves push on the aortic semilunar valve . With age, the aorta stiffens such that the pulse wave is propagated faster and reflected waves return to the heart faster before the semilunar valve closes, which raises the blood pressure . The stiffness of the aorta is associated with a number of diseases and pathologies, and noninvasive measures of the pulse wave velocity are an independent indicator of hypertension . Measuring the pulse wave velocity (invasively and non-invasively) is a means of determining arterial stiffness . Maximum aortic velocity may be noted as V or less commonly as AoV . </P> <P> Mean arterial pressure (MAP) is highest in the aorta and the MAP decreases across the circulation from aorta to arteries to arterioles to capillaries to veins back to atrium . The difference between aortic and right atrial pressure accounts for blood flow in the circulation . When the left ventricle contracts to force blood into the aorta, the aorta expands . This stretching gives the potential energy that will help maintain blood pressure during diastole, as during this time the aorta contracts passively . This Windkessel effect of the great elastic arteries has important biomechanical implications . The elastic recoil helps conserve the energy from the pumping heart and smooth out the pulsatile nature created by the heart . Aortic pressure is highest at the aorta and becomes less pulsatile and lower pressure as blood vessels divide into arteries, arterioles, and capillaries such that flow is slow and smooth for gases and nutrient exchange . </P> <Ul> <Li> Aortic aneurysm--mycotic, bacterial (e.g. syphilis), senile, genetic, associated with valvular heart disease </Li> <Li> Aortic coarctation--pre-ductal, post-ductal </Li> <Li> Aortic dissection </Li> <Li> Aortic stenosis </Li> <Li> Aortitis, inflammation of the aorta that can be seen in trauma, infections, and autoimmune disease </Li> <Li> Atherosclerosis </Li> <Li> Ehlers--Danlos syndrome </Li> <Li> Marfan syndrome </Li> <Li> Trauma, such as traumatic aortic rupture, most often thoracic and distal to the left subclavian artery and often quickly fatal </Li> <Li> Transposition of the great vessels, see also dextro - Transposition of the great arteries and levo - Transposition of the great arteries </Li> </Ul> <Li> Aortic aneurysm--mycotic, bacterial (e.g. syphilis), senile, genetic, associated with valvular heart disease </Li>

Which of the following is not one of the three branches the arising from the descending aorta