An obturator assembly (100) for penetrating tissue and being at least partially positionable within a cannula assembly (100) includes an obturator housing (102), a penetrating member (e.g. blade) and an obturator shield (106). The obturator shield is movable between an extended position where the penetration member is substantially enclosed and a retracted position where the penetrating member is at least partially exposed. An activator member (116) is adapted for movement between an initial position where the shield is secured in the extended position, permitting the shield to move to expose the penetrating member. The obturator assembly may further include a latch member (180) to secure the shield in the extended position. The latch member can release the shield when the housing is mated with the cannula assembly provided the activator member is in the release position. The obturator assembly further includes a release member (182) which engages the cannula assembly to thereby displace the release member and cause actuation of the latch member.
