Definition
The base of the skull is called base cranii in anatomical terminology and is a part of the neurocranium. The skull (lat. Cranium) is divided into the viscerocranium (facial skull) and the neurocranium (cerebral skull). The base of the skull is divided into the base cranii interna, the side facing the brain, and the base cranii externa, the outside. In the rear part of the external base of the skull, it also molds the contours of the brain, while in the front part, the external base of the skull is involved in the formation of the nasal cavities and the hard palate.
Base cranii interna
The inside of the base of the skull can be divided into three skull pits, which are separated from each other in steps. A distinction is made between the anterior, media and posterior cranial fossa, i.e. the anterior, middle and posterior cranial fossa.
Fossa cranii anterior
The frontal fossa is mainly formed by the Os frontale (frontal bone) and the Os sphenoidale (sphenoid bone). The Os ethmoidale (ethmoid bone) has only a small part of the frontal fossa. The Fossa cranii anterior supports the frontal lobe of the cerebrum and forms the roof of the orbit, in addition it is involved in the formation of the nasal cavity. Through the os ethmoidale, the olfactory filaments run from the olfactory bulb, which lies in the fossa cranii anterior, to the nasal mucosa. The anterior fossa has a passage for the optic nerve and the ophthalmic artery, which supplies the eyeball with blood, at the transition to the medial fossa with the optic canalis.
Fossa cranii media
The middle cranial fossa consists of a right and a left part, both of which are constructed in exactly the same way, and houses the two temporal lobes of the cerebrum. The bony structure consists mainly of the Os temporale (temporal bone) and additionally of the Os sphenoidale (sphenoid bone). In the sella turcica (Turkish saddle) of the sphenoid bone is the pituitary gland, the hormone-producing pituitary gland.
Through a gap in the sphenoid bone, the superior orbital fissure, the cranial nerves III, IV, V1 and VI move towards the eye muscles to innervate them motorically. In addition, a nerve to supply the upper jaw (maxillary nerve) runs through the rotundum foramen and a nerve to supply the lower jaw (mandibular nerve) through the oval foramen. In the medial fossa of the skull, the carotid canal is also found as a passageway for the internal carotid artery, which supplies the brain with blood.