Superior view of the bony skull base. The cranial compartment is separated into three fossae: anterior, middle and posterior. The anterior fossa floor is mostly made up on the frontal bone; in the midline, the ethmoid sinuses are present. The crista galli is the intracranial part of the perpendicular plate of the ethmoid bone. The sphenoid bone separates the anterior and middle cranial fossae, and contains a depression called the sella turcica for the pituitary gland. The sella turcica is bordered anteriorly by the tuberculum sella and posteriorly by the dorsum sella. The sphenoid bone also contains numerous foramina for nerves and vessels to enter & exit the skull base: the optic canal, superior orbital fissure, foramen rotundum, foramen ovale, and foramen spinosum are all within the sphenoid bone. The temporal bone comprises the majority of the floor of the middle cranial fossa, and the posterior fossa is primarily surrounded by the occipital bone and petrous portion of the temporal bone. The occipital bone contains the midline foramen magnum and paired hypoglossal canals; the jugular foramen is formed by the junction of the sphenoid and occipital bones. (Image courtesy of AL Rhoton, Jr.)