During cranial motion, the paired bones move with which rotations?

• A. Internal rotation only
• B. External rotation only
• C. Internal and external rotation
• D. No rotation

Answer: (C)

The key concept is that cranial motion is bidirectional and involves subtle rotations of the cranial bones, not a single direction. In the primary respiratory mechanism, the paired bones rotate in both directions during the cycle: they engage in internal rotation during one phase and external rotation during the opposite phase as the system flexes and then extends. This reciprocal rotation is possible because the cranial sutures and membranes allow slight twisting while maintaining overall integrity of the skull. So, the paired bones do not rotate only one way or not rotate at all; they undergo internal and external rotations as part of the cranial rhythmic movement.