NCBTMB Exam 2025 – 400 Free Practice Questions to Pass the Exam

The posterior wall of the pelvis is formed by the sacrum. The sacrum is a triangular bone located at the base of the spine, consisting of fused vertebrae. Its position and structure provide a crucial support role for the pelvis, acting as an anchor for the pelvic girdle and facilitating weight transfer from the upper body to the lower limbs. The sacrum also contributes to the formation of the sacroiliac joints, where it articulates with the ilia, further emphasizing its role in pelvic stability and mobility.

In the context of the other options, the ilia are part of the lateral wall of the pelvis, and while they are significant in forming the pelvic structure overall, they do not make up the posterior wall. The coccyx, often referred to as the tailbone, sits at the very bottom of the spine but is considered part of the pelvic floor rather than the wall. The pubis is situated anteriorly in the pelvic structure, making it part of the front wall rather than the back. This anatomical understanding clarifies why the sacrum is the definitive answer for the structure that forms the posterior wall of the pelvis.