Which structure forms the boundary of the superior opening of the true pelvis?

Which structure forms the boundary of the superior opening of the true pelvis?

• A. Acetabular Roof
• B. Iliac Crest
• C. Pelvic Inlet
• D. Pubic Symphysis

Answer: (C)

Understanding where the true pelvis begins is key. The superior opening of the true pelvis is the pelvic inlet (pelvic brim). It forms a ring of bone—the sacral promontory at the back, the ilium’s ala and arcuate line laterally, and the pubic arch/crest anteriorly up to the pubic symphysis. This boundary separates the true pelvis from the false pelvis. The other structures don’t define the entire boundary: the acetabular roof is part of the hip socket, the iliac crest is simply the top edge of the ilium, and while the pubic symphysis lies at the front, it does not by itself form the whole boundary of the pelvic inlet.

Understanding where the true pelvis begins is key. The superior opening of the true pelvis is the pelvic inlet (pelvic brim). It forms a ring of bone—the sacral promontory at the back, the ilium’s ala and arcuate line laterally, and the pubic arch/crest anteriorly up to the pubic symphysis. This boundary separates the true pelvis from the false pelvis. The other structures don’t define the entire boundary: the acetabular roof is part of the hip socket, the iliac crest is simply the top edge of the ilium, and while the pubic symphysis lies at the front, it does not by itself form the whole boundary of the pelvic inlet.