 Pulmonary valve

The pulmonary valve is the heart valve between the right ventricle and pulmonary trunk. During forward ventricular ejection it allows blood to enter the pulmonary circulation; closure limits return from the pulmonary trunk into the relaxing right ventricle.^[ref]

Its pocket-like cusps respond to the changing pressure difference. Unlike the tricuspid valve, the pulmonary valve has no attached chordae tendineae or papillary muscles.^[ref] Thus the same direction-control task is achieved by different supporting structures at the chamber inlet and outlet.

A deliberately idealized valve model sets forward blood flow to zero when the downstream pressure exceeds the upstream pressure, and permits positive flow when ventricular pressure exceeds trunk pressure. This model captures direction but omits the inertia and deformation of real cusps. It is useful for checking the sign of a flow term, not for predicting an exact opening time.

For example, if a constructed cycle sends 80 mL forward and 10 mL backward across the pulmonary valve, net transport is 70 mL. Counting only the positive part of blood flow overestimates net delivery. This is why stroke volume inferred from changing chamber volume and net forward flow in the pulmonary trunk require compatible assumptions about valve function.