In which direction must the lateral angles (occipital squamae) move to cause the basi-occiput to shift toward the left?

In which direction must the lateral angles (occipital squamae) move to cause the basi-occiput to shift toward the left?

• A. Left around its vertical axis
• B. Right around its vertical axis
• C. Front around its sagittal axis
• D. Back around its sagittal axis

Answer: (B)

Movement of the occipital squamae around the vertical axis translates the base of the occiput (basi-occiput) in the opposite horizontal direction. When the lateral angles rotate to the right around the vertical axis, they pull the occipital base so that the basi-occiput shifts toward the left. This happens because the occiput behaves like a rotating block on a vertical axis: a rightward rotation of the lateral angles generates a leftward displacement of the basilar portion. In contrast, rotating around a sagittal axis would tilt or flex/extend rather than produce a pure left-right shift, and rotating to the left would move the basi-occiput to the right.

Movement of the occipital squamae around the vertical axis translates the base of the occiput (basi-occiput) in the opposite horizontal direction. When the lateral angles rotate to the right around the vertical axis, they pull the occipital base so that the basi-occiput shifts toward the left. This happens because the occiput behaves like a rotating block on a vertical axis: a rightward rotation of the lateral angles generates a leftward displacement of the basilar portion. In contrast, rotating around a sagittal axis would tilt or flex/extend rather than produce a pure left-right shift, and rotating to the left would move the basi-occiput to the right.