What is the definition or description of: aortic valve?

Exit door of heart: The aortic valve is one of 4 valves in the heart, each of which separates 2 cardiac chambers. It opens when blood is actively ejected from the left ventricle into the aorta artery, to be carried to the rest of the body. It then closes firmly to prevent blood from flowing backwards, while it passively continues to flow forward to body's vital organs. When next heartbeat comes, it opens again.

See below: The aortic valve is a 3 leaflet valve which lies on the top of the main pumping chamber of the heart (left ventricle) and at the beginning of the aorta. The blood exiting the heart under high pressure passes thru the aortic valve into the main artery (aorta). It is about 1-1.5 inches in diameter.