This cross-sectional segment is bounded superiorly by a virtual horizontal plane at the level of the plane traversing the superior boundary of the iliac crest; and inferiorly it extends to the perineum and includes part but not necessarily the entire external genitalia. The segment includes the volume of the true and false pelvic cavities (and also part of the lower abdominal volume below the level of the virtual superior boundary). The volume includes the entire transverse thickness of the body over the longitudinal extent between the superior (upper) and inferior (lower) boundaries including the skin and subcutaneous tissue. The segment relates to the cross-sectional or projectional volume as perceived by transmissive or emissive imaging.