Ascending aorta

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Anatomy and branches of the thoracic (descending) aorta.

The ascending aorta is the first segment of the aorta as it emerges from the base of the left ventricle. At its origin at the aortic orifice is the aortic semilunar valve, which separates the ascending aorta from the left ventricle. From its origin, it ascends anteriorly and to the right, passing posterior to the left half of the sternum where it transitions into becoming the aortic arch, roughly at the level of the sternal angle (manubriosternal joint). It is roughly 5cm in length and is the widest segment of the aorta, typically between 3-4cm in diameter.

The ascending aorta is found in within the fibrous pericardium together the pulmonary trunk which sits anterior to its lower half, whilst the left atrium, right pulmonary artery and the right primary bronchus are located posterior to it. On its right is the superior vena cava and right atrium, and to its left is the left atrium and pulmonary trunk (apart from the lower section). 

Only two arteries originate from the ascending aorta: the left and right coronary arteries. The coronary arteries arise just superior to the aortic semilunar valve and are responsible for providing nutrient-rich, oxygenated blood to the myocardium.