A bioreactor system includes a sample chamber capable of receiving a specimen and a cover which can be placed on the chamber to enclose the specimen within the chamber. A first member is movable between (i) a closed position in which the member restricts the cover from being moved away from the chamber in a first direction, and (ii) an open position in which the member does not restrict the cover from being moved away from the chamber. When the first member is in the closed position there is a substantially liquid proof seal between the cover and the chamber.