Valve assembly including diameter reduction structure for trocar

A surgical system, which comprises:

• a cannula assembly including a cannula housing and a cannula sleeve extending from the cannula housing, the cannula sleeve defining a longitudinal axis and having a longitudinal passageway to permit passage of a surgical instrument;
• a second seal subassembly including a second housing adapted for mounting to the cannula housing, a lock member secured to the second housing and adapted for rotational movement relative to the longitudinal axis to cause corresponding rotational movement of the second housing between a first position and a second position, the second housing having an annular member defining a central aperture for passage of the surgical instrument and a plurality of internal mounting recesses communicating with the central aperture, and a manual grip member connected to the lock member and depending radially outwardly relative to the longitudinal axis to extend external of the second housing, the manual grip member being directly movable by the surgeon to move the lock member and to cause the corresponding rotational movement of the second housing between the first and second positions thereof;
• and
• a first seal subassembly for releasably mounting to the second seal subassembly, the first seal subassembly including a seal member adapted to permit passage of a surgical object in substantial sealed relation therewith and a first housing having a plurality of internal mounting tabs configured to be received or released by the mounting recesses of the second housing when the second housing is in the first position and to be secured to the second housing when the second housing is in the second position.