Sacral cornua result from the failure of laminae of which vertebra to form and fuse?

Sacral cornua result from the failure of laminae of which vertebra to form and fuse?

• A. S4
• B. S3
• C. S5
• D. L5

Answer: (C)

Sacral cornua are the small horns on either side of the lower sacrum that come from the inferior articular processes of the last sacral vertebra. During development, the laminae of the final sacral segment (S5) normally fuse with the sacrum to form its posterior wall. If those laminae fail to form or fuse, the inferior articular processes remain as separate projections—the sacral cornua. That’s why the vertebra involved is the last sacral segment, S5. The other options lie above or outside the sacrum and wouldn’t give rise to these horn-like structures.

Sacral cornua are the small horns on either side of the lower sacrum that come from the inferior articular processes of the last sacral vertebra. During development, the laminae of the final sacral segment (S5) normally fuse with the sacrum to form its posterior wall. If those laminae fail to form or fuse, the inferior articular processes remain as separate projections—the sacral cornua. That’s why the vertebra involved is the last sacral segment, S5. The other options lie above or outside the sacrum and wouldn’t give rise to these horn-like structures.