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

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

• A. Left around its vertical axis
• B. Right around its vertical axis
• C. Up around its horizontal axis
• D. Down around its vertical axis

Answer: (A)

Movement of the occipital squama’s lateral angles around a vertical axis creates a torsional rotation of the occiput. When the left lateral angle moves to the left around that vertical axis, the occipital base (basi-occiput) is carried to the right. This opposite-direction shift comes from how the occipital bone twists about the foramen magnum and how the squama and basilar part relate at the cranial base. So the leftward motion of the left lateral angle around the vertical axis results in the basi-occiput moving to the right. (Movements around a horizontal axis would affect flexion/extension, and moving the right lateral angle would produce the opposite effect.)

Movement of the occipital squama’s lateral angles around a vertical axis creates a torsional rotation of the occiput. When the left lateral angle moves to the left around that vertical axis, the occipital base (basi-occiput) is carried to the right. This opposite-direction shift comes from how the occipital bone twists about the foramen magnum and how the squama and basilar part relate at the cranial base. So the leftward motion of the left lateral angle around the vertical axis results in the basi-occiput moving to the right. (Movements around a horizontal axis would affect flexion/extension, and moving the right lateral angle would produce the opposite effect.)