has part has part has_part subdivision of skeletal system bony pelvis skeletal system of pelvis A ring of bone formed by the sacrum and the first few coccygeal vertebrae as the roof, the pubis and ischia as the floor and the ilia and the acetabular part of the ischia as the walls. pelvis ossea UBERON:0001270 SCTID:46633002 FMA:16580 ischium pubis pelvic region of trunk fused sacrum