Petrous part of temporal bone

The petrous part of temporal bone has a triangular or pyramid-like shape, with its apex directed forward and inward, and its base facing outward and to the side. Positioned between the sphenoid bone's greater wing and the basilar portion of the occipital bone, this pyramidal portion of the temporal bone features three surfaces—anterior, posterior, and inferior—and three edges. The anterior and posterior surfaces are part of the middle and posterior cranial fossae, respectively, while the inferior surface is visible from the skull’s base view, known as the norma basalis. Inside, the petrous part of temporal bone encases the structures of the middle and inner ears.