Uptick

During the expansion (uptick) or flexion phase of cranio-sacral motion, the anterior portion of the maxillae rises superiorly coming up to meet the frontal bone that is arching forward and down, as the second illustration suggests. This uptick of the facial complex slightly spreads the posterior part of the intermaxillary suture as the back teeth move slightly apart.

The maxillary-palatine-vomer complex also pushes slightly anterior with each expansion phase, as it also arcs upward to meet the frontal bone, during sphenoid counterrotation on the occipital, or during the narrowing of the angle between the posterior palatine and the anterior mastoid process.

From the inside view of the skull, on the side where cranio-sacral flexion commonly is found, the left sphenoid arcs forward and downward, during the expansion phase, moving the ethmoid forward and up, hinging around the sphenoid. This illustration is in contrast to the upper illustration where cranial-sacral compression (downtick) of the anterior occiput on the posterior sphenoid is depicted.