View of the right pterion. For perspective, the right side of the image is anterior. The pterion is the H-shaped region where four cranial bones meet: the squamosal portion of the temporal bone, the greater wing of the sphenoid bone, and the frontal and parietal bones. The MacCarty keyhole is a surgical landmark designed to simultaneously expose the floor of the anterior cranial fossa and the orbit, and is classically described near the junction of the frontal, sphenoid and zygomatic bones. Anterior to this, the frontal and zygomatic bones meet at the frontozygomatic suture. A combination of seven bones make up the orbit: the frontal bone (superior), the zygomatic bone (lateral), the maxilla (inferior), the ethmoid and lacrimal bones (medial), and the sphenoid and palatine bones (deep, posterior). The optic canal, superior and inferior orbital fissures are foramina in the posterior orbit bordering the sphenoid bone. (Image courtesy of AL Rhoton, Jr.)