A pressure activated valve comprises a housing having a lumen extendingtherethrough . A flow control membrane extending across the lumen includes amounting portion at which the flow control membrane is coupled to the housingand a lumen occluding portion having a slit extending therethrough . When thelumen-occluding portion is subjected to a pressure of at least a predeterminedlevel, the lumen-occluding portion moves from a closed configurationpreventing flow through the lumen to an open configuration permitting flow. Athickness of the mounting portion is greater than a thickness of the lumen-occluding portion.
