The sacrum is formed by fused vertebrae and serves as which structure?

• A. Tailbone
• B. Nerve bundle inside vertebral canal
• C. Fused vertebrae forming pelvis base
• D. Distributive shock from spinal cord injury causing vasodilation

Answer: (C)

The sacrum serves as the fused block that forms the base of the spine and the posterior part of the pelvic girdle. It’s made of five fused sacral vertebrae and anchors to the ilia at the sacroiliac joints, creating a strong pelvic ring that transmits body weight from the spine to the pelvis and legs. That’s why the correct description is fused vertebrae forming the pelvis base.

Tailbone refers to the coccyx, which is below the sacrum, not the sacrum itself. The sacrum does house openings for sacral nerves, but it isn’t a single nerve bundle inside the vertebral canal. Distributive shock is a physiologic consequence, not a structural role of the bone.