It is that part of the trunk below the pelvic inlet. Its funnel-shaped cavity extends backward and downward from the abdominal cavity proper. The part of the abdominal cavity that lies between the iliac fossae is known as the greater (or false) pelvis. The thorax, abdomen, and pelvis are (together with the back) parts of the trunk. The thoracic and abdominal cavities are separated from each other by the diaphragm. The abdominal cavity proper and the true pelvic cavity are continuous across the plane of the pelvic inlet, or brim (see fig. 31-3).