A system for manipulating tissue, the system comprising: an access cannula having a distal end and a lumen; a cannula adapter fixed or releasably attached to said access cannula; and a deformable conduit assembly comprising a deformable conduit with a length allowing the deformable conduit to extend through and be operable beyond the distal end of the access cannula, the lumen of the access cannula dimensioned to allow said deformable conduit to be disposed within said access cannula, a hub defining a central passage with said deformable conduit slidably disposed within said central passage, and an axial controller fixed to a proximal end of said deformable conduit; wherein said cannula adapter is configured to cooperate with said hub to releasably fix said access cannula to said deformable conduit in an axial direction, wherein the deformable conduit is adapted to be connected with a steerable instrument or with other devices via the hub, said steerable instrument actuatable to adjust curvature of said deformable conduit between a substantially straight configuration and a curved configuration, and wherein said deformable conduit is adapted to be deformed from a normally straight configuration into a deformed configuration by the steerable instrument, characterized in that: when the access cannula is releasably fixed to the hub, said hub is prevented from moving in the axial direction relative to said access cannula, and said axial controller is configured to urge the deformable conduit in the axial direction relative to the hub and said access cannula without moving said access cannula or said hub in the axial direction. an access cannula having a distal end and a lumen; a cannula adapter fixed or releasably attached to said access cannula; and a deformable conduit assembly comprising a deformable conduit with a length allowing the deformable conduit to extend through and be operable beyond the distal end of the access cannula, the lumen of the access cannula dimensioned to allow said deformable conduit to be disposed within said access cannula, a hub defining a central passage with said deformable conduit slidably disposed within said central passage, and an axial controller fixed to a proximal end of said deformable conduit; wherein said cannula adapter is configured to cooperate with said hub to releasably fix said access cannula to said deformable conduit in an axial direction, wherein the deformable conduit is adapted to be connected with a steerable instrument or with other devices via the hub, said steerable instrument actuatable to adjust curvature of said deformable conduit between a substantially straight configuration and a curved configuration, and wherein said deformable conduit is adapted to be deformed from a normally straight configuration into a deformed configuration by the steerable instrument, characterized in that: when the access cannula is releasably fixed to the hub, said hub is prevented from moving in the axial direction relative to said access cannula, and said axial controller is configured to urge the deformable conduit in the axial direction relative to the hub and said access cannula without moving said access cannula or said hub in the axial direction.