Surgical instruments and end effectors therefor are disclosed. In various implementations, the surgical instrument includes a surgical end effector (4120) that comprises a lower jaw (4104) and an upper jaw (4020) that are supported for movable travel toward and away from each other. The instrument may further include a firing member (4610) that is operably supported for selective operable travel within the surgical end effector. The instrument may also include a first jaw closure system (200) that operably interfaces with the lower jaw and is configured to selectively move the lower jaw relative to the upper jaw. A second jaw closure system (4110) operably interfaces with the upper jaw and is configured to selectively move the upper jaw relative to the lower jaw. A firing system operably interfaces with the firing member and is configured to apply firing motions to the firing member to move the firing member within the end effector.
