Pulmonary valve annulus (anatomy)

The pulmonary valve annulus is part of the fibrous skeleton of the heart. It is a subendocardial connective tissue thickening which has a similar structure to the aortic valve annulus:

• three arches which surround the pulmonary valve orifice
• the luminal surface of the arches merges with the lamina fibrosa of the valve leaflets
• the apices of the arches merge along the line of the valve commissures
• the region inferior to each arch forms a continuum of fibrous tissue that blends with the pulmonary infundibulum

However, the valves' annuli differ in that:

• they are not in the same plane, unlike the atrioventricular valve annuli; the pulmonary valve annulus is roughly perpendicular to the aortic valve annulus
• the proximal, most inferior part of each arch of the pulmonary valve is not thickened, unlike the aortic valve

The region intermediate to the arches of the pulmonary annulus which support the right and left leaflets of the valve is continuous with the tendon of the infundibulum. This provides a fibrous connection between the pulmonary and aortic valves.