Port closure systems and ways of using such systems are provided that include a port, a valve, and a keyway. The port establishes communication between an exterior environment and an interior volume that can receive a fluent substance. A first conduit leading to the exterior environment and a second conduit leading to the interior volume are defined by the port, where the first conduit and the second conduit follow an axis. The valve includes a flexible, resilient head extending across the port between the first conduit and the second conduit. The keyway is formed in the first conduit and defines a channel extending along the axis. The system can include a valve connector having a stem configured to be received within the port, where the stem can extend through the first conduit, the valve, and into the second conduit. The stem includes a key receivable by the keyway.
