A surgical system for penetrating tissue, which comprises: a cannula assembly including: a cannula housing; a cannula sleeve depending from the cannula housing and defining a longitudinal axis; an object seal disposed relative to the cannula housing and being adapted to establish a substantial seal about an object inserted therethrough; and a cover mounted to the cannula housing and having a cover aperture therethrough, the cover having a trailing end face, at least a portion of the trailing end face being obliquely arranged relative to the longitudinal axis and terminating in, and leading toward, the cover aperture to facilitate guiding of the surgical object through the cover aperture; and an obturator assembly at least partially positionable within the cannula assembly, the obturator assembly including: an obturator housing having a housing base defining a leading end face, and an obturator member extending from the obturator housing and having a leading penetrating member adapted to penetrate tissue; characterized in that: the trailing end face of the cover defines a predetermined geometric configuration, the predetermined geometric configuration being a substantial recessed portion having a generally diamond shaped configuration, key shaped configuration or the particular configuration depicted in Figure 11; and the leading end face of the obturator housing defines a predetermined geometric configuration corresponding to the predetermined geometric configuration of the trailing end face of the cover to mate therewith upon assembly of the obturator assembly with the cannula assembly. a cannula assembly including: a cannula housing; a cannula sleeve depending from the cannula housing and defining a longitudinal axis; an object seal disposed relative to the cannula housing and being adapted to establish a substantial seal about an object inserted therethrough; and a cover mounted to the cannula housing and having a cover aperture therethrough, the cover having a trailing end face, at least a portion of the trailing end face being obliquely arranged relative to the longitudinal axis and terminating in, and leading toward, the cover aperture to facilitate guiding of the surgical object through the cover aperture; and a cannula housing; a cannula sleeve depending from the cannula housing and defining a longitudinal axis; an object seal disposed relative to the cannula housing and being adapted to establish a substantial seal about an object inserted therethrough; and a cover mounted to the cannula housing and having a cover aperture therethrough, the cover having a trailing end face, at least a portion of the trailing end face being obliquely arranged relative to the longitudinal axis and terminating in, and leading toward, the cover aperture to facilitate guiding of the surgical object through the cover aperture; and an obturator assembly at least partially positionable within the cannula assembly, the obturator assembly including: an obturator housing having a housing base defining a leading end face, and an obturator member extending from the obturator housing and having a leading penetrating member adapted to penetrate tissue; an obturator housing having a housing base defining a leading end face, and an obturator member extending from the obturator housing and having a leading penetrating member adapted to penetrate tissue; characterized in that: the trailing end face of the cover defines a predetermined geometric configuration, the predetermined geometric configuration being a substantial recessed portion having a generally diamond shaped configuration, key shaped configuration or the particular configuration depicted in Figure 11; and the leading end face of the obturator housing defines a predetermined geometric configuration corresponding to the predetermined geometric configuration of the trailing end face of the cover to mate therewith upon assembly of the obturator assembly with the cannula assembly. the trailing end face of the cover defines a predetermined geometric configuration, the predetermined geometric configuration being a substantial recessed portion having a generally diamond shaped configuration, key shaped configuration or the particular configuration depicted in Figure 11; and the leading end face of the obturator housing defines a predetermined geometric configuration corresponding to the predetermined geometric configuration of the trailing end face of the cover to mate therewith upon assembly of the obturator assembly with the cannula assembly.