Fossa cranii posterior
The occipital bone is mainly involved in the formation of the posterior fossa, the temporal bone and the sphenoid bone have smaller parts of the bony structure. The posterior fossa contains the occipital lobe of the cerebrum in its upper part and the cerebellum in its lower part. In the bones of the posterior fossa there are imprints of the sinuses, the venous blood conductors of the brain.
In addition, the largest point of passage of the skull base, the foramen magnum, is also found here. The foramen magnum accommodates the medulla oblongata and blood vessels, it connects the posterior fossa of the skull with the spinal canal. With the porus acusticus internus (internal auditory canal), the posterior fossa also contains the passageway for the eighth cranial nerve, which is responsible for the sense of hearing and the sense of balance.
Base cranii externa
The outside of the skull-base forms the Choanen with its front-part, the rear openings of the nose-caves. Also the upper jaw and the bony palate belong to the outside of the skull base. In the rear part of the outer skull base are the condyli occipitales (occipital condyles), which are connected to the first vertebral body.
Injuries
A basilar skull fracture is a potentially life-threatening injury that often occurs in the course of traffic accidents. Depending on the direction of the applied force, the base of the skull fractures along certain fracture lines. These fracture lines are particularly thin sections of the bony structure.
In the area of the anterior fossa of the skull, the bone plate of the os ethmoidale (ethmoid bone) is very thin, which is why fractures occur particularly frequently here in accidents. A consequence of a bone fracture in this area can be a tear in the dura, the hard meninges, since the dura has grown together with the bone in this area. Another consequence can be the loss of the sense of smell due to a break in the olfactory filaments, as these pass through the ethmoid bone at this point and can be injured in the event of a fracture.In this so-called frontobasal fracture, cerebrospinal fluid (liquor) often leaks out of the nose because the tear in the hard meninges means that the liquor can no longer be retained and now runs out of the nose.
In addition, blood vessels can be damaged and blood can run out of the nose. In the case of a lateral skull base fracture, the meninges and vessels in the middle fossa of the skull can be injured and blood and cerebrospinal fluid can run out of the ear on the affected side. Other symptoms of a basal skull fracture are severe headaches, vomiting or loss of consciousness.
