Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

During cranial/sacral extension, which direction do the midline bones move?

1. Extend and rise

2. Lower and exhale

3. Flex and rotate externally

4. Nutate and inhale

The correct answer is: Lower and exhale

In the context of cranial/sacral rhythm, when discussing the movement of the midline bones during cranial extension, it is essential to understand the mechanics of cranial motion. During cranial/sacral extension, the midline bones, which include the frontal, parietal, occipital, and the sphenoid, move in a coordinated manner. Typically, in cranial extension, the primary action involves these midline bones moving into a more superior position, or ‘rising’. This movement is part of the physiological design of the cranial motion cycle, where the body engages in a rhythmic pattern of inhalation and exhalation. As the midline bones rise, various osteopathic principles describe this phase as an "exhale" where the body is promoting homeostasis and balance. Thus, the assertion that during cranial/sacral extension, the midline bones lower and exhale reflects a correct understanding of the functional dynamics of cranial motion, although it appears contradictory at first glance. This concept ties into how the cranial base interacts with the sacrum, illustrating how extension involves coordinated movements that promote a specific biomechanical response. Therefore, this understanding aligns well with the principles of osteopathic manipulative treatment and