Aortic valve

Valva aortae

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What it is

Three half-moon (semilunar) cusps — right, left and posterior (non-coronary) — at the outlet of the left ventricle. Behind each cusp the aortic wall bulges into a sinus of Valsalva; the coronary arteries arise from the right and left sinuses.

Function

Opens during systole to let blood into the aorta and snaps shut in diastole to stop it flowing back into the left ventricle.

Size

Annulus ~20–25 mm diameter; opening area 3–4 cm².

Clinical note

Its closure makes the second heart sound (S2); age-related calcific aortic stenosis and a congenitally bicuspid valve (1–2% of people) are the commonest reasons for valve replacement.