direction toward diaphragm element 250 thereby opening inlet channel 410 to permit fluid to enter into pump chamber 240 since the fluid transport gradient during the under pressure stroke is anti parallel to the fluid flow acceptance conformation of check valve 300 the outlet slit 310 of check valve 300 constricts so as to at least partially reduce the occurrence of fluid disposed in outlet channel 420 re entering via backflow into pump chamber 240 in the alternate next phase of the stroke cycle the movement of the diaphragm element 250 in a direction which tends to reduce the pump chamber volume causes an over pressure to be generated in pump chamber 240 thereby causing fluid to flow through the outlet 310 of check valve 300 as a result of fluid flowing out of pump chamber 240 into valve inlet 340 of check valve 300 in a flow direction which causes the valve 39 s outlet slit 310 to dilate thereby permitting fluid to enter into outlet channel 420 since the fluid transport gradient during the over pressure stroke tends to press the peripheral u201c umbrella u201d flap 320 down against the pump chamber wall in the vicinity of inlet channel 410 the effect is to at least partially reduce the occurrence of fluid disposed in the pump chamber 240 from back flowing into the inlet channel 410 those skilled in the art will appreciate various other geometries and or arrangements of multiple valve components may be otherwise employed to achieve substantially the same result as the exemplary embodiments disclosed herein the same shall be regarded as within the scope and ambit of the present invention in the foregoing specification the invention has.