The prefix sacro- refers to which bone?

• A. Vertebra
• B. Pelvis
• C. Sacrum
• D. Femur

Answer: (C)

In medical terminology, prefixes point to the specific bone or structure involved. sacro- designates the sacrum, the triangular bone at the base of the spine that forms the back part of the pelvic ring. The sacrum is created by fused sacral vertebrae and connects the spine to the pelvis at the sacroiliac joints. So terms that use sacro- refer to the sacrum itself. This is different from vertebra, which would use vertebr- or spondyl- to name the individual spinal bones, or pelvis-related terms that use pelv-. The femur is the thigh bone and is named with femor- or femoral. That focus on the sacrum is why sacro- is the best choice here.