Anterior surface of petrous part

The anterior surface of petrous part of temporal bone constitutes the rear section of the middle cranial fossa's floor within the cranial cavity. It adjoins the squamous part of the temporal bone at the front, meeting it at the petrosquamous suture. This surface is distinguished by several key anatomical structures.

Medially, you will find the trigeminal impression, a subtle depression that shows where the trigeminal ganglion resides. Further out, there are openings and channels (a.k.a. hiatuses and grooves) that allow passage for the greater and lesser petrosal nerves. The greater petrosal nerve, branching off the facial nerve, travels down to the foramen lacerum to form the nerve of the pterygoid canal. The lesser petrosal nerve originates from the tympanic plexus and heads down into the foramen ovale, proceeding to the infratemporal fossa.

As you move outward, the rounded elevation known as the arcuate eminence, becomes visible. This prominence is caused by the anterior (a.k.a. superior) semicircular canal underneath it in the petrous bone. Adjacent to the arcuate eminence, there’s a recessed area on the anterior surface of petrous part called the tegmen tympani. This thin layer of bone serves as the roof of both the tympanic cavity and the mastoid antrum.