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Structural characteristics and foramina of important nerves and blood vessels

Most foramina in which relevant nerves and blood vessels pass through are located at the base of the skull. In the following the most important structures are discussed ordered by their location in the three cranial fossae. For details on the courses of the cranial nerves, please click on The 12 cranial nerves.

The anterior cranial fossa comprises a holey plate at the center, the so called cribriform plate (lamina cribrosa). The approximately 20 cribriform foramina serve as a passageway for the olfactory nerves to the olfactory mucosa in the nasal cavity. Both the optic nerve and the ophthalmic artery pass through the optic canal which is centrally located on the sphenoid bone. The lesser wing of the sphenoid bone (ala minor) forms the dorsal boundary of the anterior cranial fossa.

The middle cranial fossa lies slightly deeper than the anterior cranial fossa. The superior orbital fissure which is bounded by the greater and lesser wings of the sphenoid bone contains the trochlear nerve, abducencs nerve, oculomotor nerve and ophthalmic nerve. The sella turcica is a depression in the sphenoid bone. In the center of the middle cranial fossa it forms the pituitary fossa in which the pituitary gland sits. Further important foramina are the foramen rotundum (maxillary nerve), foramen ovale (mandibular nerve) and the carotid canal (internal carotid artery).

The largest opening in the skull is the foramen magnum. Here the brain stem leaves the skull and becomes the spinal cord. The foramen magnum is situated in the center of the posterior cranial fossa. It is separated from the middle cranial fossa by the dorsum sellae and the upper edge of the petrous bone. Further important structures are the internal acoustic meatus (facial nerve, vestibulocochlear nerve), jugular foramen (internal jugular vein, glossopharyngeal nerve, vagus nerve, accessory nerve) and the hypoglossal canal (hypoglossal nerve).

The structure of the bone of cerebrall skull. The sphenoid bone: structure, openings and their importance. The topography of the skull: external base of the skull; temporal infratemporal. The craniometry. The determination of cranial and facial index.

The sphenoid bone is an unpaired cranial bone situated at the front middle of theskull in front of the temporal bone and basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly or bat with its wings extended.

It is divided into the following parts:

· a median portion, known as the body of sphenoid bone, containing the sella turcica which houses the pituitary gland as well as the paired paranasal sinuses, the sphenoidal sinuses^[3]

· two greater wings and two lesser wings

· Pterygoid processes of the sphenoides which project from it posteriorly (below)

Two sphenoidal conchae are situated at the anterior and posterior part of the body.

The sphenoid articulates with the frontal, parietal, ethmoid, temporal, zygomatic, maxillae, palatine, vomer, and occipital bones and helps to connect the cranial skeleton to the facial skeleton.

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