Facial Skull

The facial skull is formed by the following bones: The bones of the facial skull form the basis of our face, and thus determine to a large extent how we look. While the ratio of brain to facial skull is still about 8:1 in newborns, it is only about 2:1 in adults.

The parts of the frontal bone that have an involvement in the eye socket,
The paired zygomatic bone (Os zygomaticum),
The originally in pairs put on upper jaw (Maxilla),
The paired intermaxillary bone (Os incisivum),
The unpaired lower jaw (Mandibula),
The paired nasal bone (Os nasale),
The paired nasal concha leg (Os conchale),
The paired lacrimal bone (Os lacrimale),
The paired palatine bone (Os palatinum),
The unpaired ploughshare leg (Vomer) and
The unpaired ethmoid bone (Os ethmoidale).

Base of the skull

The base of the skull describes a part of the brain skull (Neurocranium). In contrast to the facial skull (Viscerocranium), the cerebral skull directly surrounds the brain and thus fulfils a certain protective function. The base of the skull is now the lower part of this brain skull, it is formed by several bony parts.

The sphenoid bone (Os sphenoidale), the temporal bone (Os temporale), the frontal bone (Os frontale), the ethmoid bone (Os ethmoidale) and the occipital bone (Os occipitale) participate in the structure. However, the base of the skull should not be imagined as a flat structure, because due to the walnut-like shape of the brain it can be divided into three pits. The anterior cranial fossa (Fossa cranii anterior) is furthest from the face, the posterior cranial fossa (Fossa cranii posterior) is located in the occipital region, and a medial cranial fossa (Fossa cranii media) is located exactly between the anterior and posterior cranial fossa.

Each of these pits has characteristic holes (foramina). These holes serve as passage points for various nerves, arteries and veins. In addition, each fossa can be assigned a brain section.

The anterior cranial fossa (Fossa cranii anterior) contains mainly the anterior part of the brain (frontal lobe) and the olfactory nerve, which is important for olfactory perception. It is formed by the frontal bone (Os frontale), parts of the ethmoid bone (Os ethmoidale) and sections of the sphenoid bone (Os sphenoidale).The middle cranial fossa (Fossa cranii media) is mainly bounded by the sphenoid bone and the temporal bone, it contains mainly the lateral part of the brain (temporal lobe) and the pituitary gland. It contains most of the points of passage and thus the medial fossa also has the most connections to other cavities of the bony skull.

The most important connections are: The posterior part of the cranial base, formed by the posterior fossa (Fossa cranii posterior), is limited by parts of the temporal bone and the occipital bone. In this section of the skull base further small depressions can be seen. In these depressions the cerebellum and the venous outflow channels (sinus) are located.

Within the posterior fossa of the skull there are mainly connections to the ear (via the porus acusticus internus) and to the spinal canal (via the foramen magnum). Both the auditory and vestibular nerves reach the inner ear via the porus acusticus internus. The foramen magnum is located entirely in the occipital bone and represents the most important connection between the brain and the spinal canal, because both the extended brain stem together with the meninges and the pathways supplying the spinal cord pass through this opening in the skull base.

Based on the anatomical conditions just explained, it is possible to understand why a fracture of the skull base can be classified as life-threatening. Violence, mostly in the course of traffic accidents, causes fractures of the anterior, middle and in rare cases also of the posterior fossa of the skull. Frequent symptoms are severe headaches, vomiting, the discharge of blood and cerebrospinal fluid (liquor) from the nose or ears and disturbances of consciousness.

Canalis opticus (between the base of the skull and the eye socket), this is where the optic nerve (nervus opticus) and the artery that supplies the eye socket and the eye itself (arteria ophthalmica) run.
Superior orbital fissure (between the base of the skull and the eye socket), through which mainly the eye muscle nerves (occulomotor nerve, trochlear nerve and abducens nerve) and the sensitive nerve of the upper half of the face (ophthalmic nerve) pass.
Foramen rotundum (between the base of the skull and the dorsal fossa), through which the maxillary nerve passes.
Foramen ovale (conducts pathways from the skull base out of the skull) with the mandibular nerve (nervus mandibularis).