A, The temporal bone has a squamosal part, which forms some of the floor and lateral wall of the middle cranial fossa. It is also the site of the mandibular fossa in which the mandibular condyle sits. The tympanic part forms the anterior, lower, and part of the posterior wall of the external canal, part of the wall of the tympanic cavity, the osseous portion of the eustachian tube, and the posterior wall of the mandibular fossa. The mastoid portion contains the mastoid air cells and mastoid antrum. The petrous part is the site of the auditory and vestibular labyrinth, the carotid canal, the internal acoustic meatus, and the facial canal. The petrous part also forms the anterior wall and the dome of the jugular fossa. The styloid part projects downward and serves as the site of attachment of three muscles. B, Inferior view of the temporal and surrounding bones. The squamosal and petrous parts articulate anteriorly with the greater wing of the sphenoid. The petrous apex faces the foramen lacerum and is separated from the clival part of the occipital bone by the petroclival fissure. The occipital bone joins with the petrous part of the temporal bone to form the jugular foramen. The mandibular fossa is located between the anterior and posterior roots of the zygomatic process. C, The medial part of the upper surface is the site of the trigeminal impression in which Meckel’s cave sits. Farther laterally is the prominence of the arcuate eminence overlying the superior semicircular canal. Anterolateral to the arcuate eminences is the tegmen, a thin plate of bone overlying the mastoid antrum and epitympanic area. The temporal bone articulates anteriorly with the sphenoid bone, above with the parietal bone, and posteriorly with the occipital bone. The zygomatic process of the squamosal part has an anterior and a posterior root between which, on the lower surface, is located the mandibular canal. D, Temporal and surrounding bones. The squamosal part of the temporal bone joins anteriorly with the sphenoid bone to form the floor of the middle cranial fossa. Posteriorly, it articulates with the occipital bone to form a portion of the anterior wall of the posterior fossa. Medially, it articulates with the clival portion of the occipital bone at the petroclival fissure. The sigmoid sulcus descends along the posterior surface of the mastoid portion and turns forward to enter the jugular foramen. The foramen lacerum is located at the junction of the temporal, sphenoid, and occipital bones. The porus of the internal acoustic meatus is located in the central part of the posterior surface. (Images courtesy of AL Rhoton, Jr.)