The true pelvis, or pelvis minor, contains a basin-like cavity inferior to the superior aperture, while the false pelvis, or pelvis major, is a wider, heart-shaped cavity found superior to the plane that goes through the linea terminalis, according to The Free Dictionary by Farlex. Both are encased within the pelvic girdle.
The superior aperture, also known as the superior circumference, is what shapes the brim of the much wider portion of the pelvis and also forms the heart-shaped anatomy that makes up the false pelvis, notes Gray's Anatomy. This area supports the intestines and is considered part of the abdominal cavity.
The true pelvis is found below the pelvic brim of the superior aperture, and it makes up the space between the pelvic floor and the pelvic inlet, according to Gray's Anatomy. The lesser pelvis, unlike the abdominal cavity, contains the sex organs, colon, bladder and rectum. This is all found below the linea terminalis, which is at the edge of the pelvic inlet that separates the abdominal and pelvic cavities. The opening of the pelvis rounds out the bottom portion of the cavity formed by the lesser pelvis. Both the true pelvis and the false pelvis make up the pelvic girdle, which is shaped by the hip bones, sacrum, coccyx and pubic arch.