Coronal section - Cranial Nerves exiting the cranial cavity
The coronal section of the head and neck region shows the twelve cranial nerves exiting the cranial cavity. Below is a brief description of the same:
Olfactory nerve :
The olfactory nerve is the first cranial nerve. It contains sensory nerve fibers relating to the sense of smell.
Cribriform plate of the ethmoid bone :
The cribriform plate is a sieve-like porous plate of the palatine bone that form the roof of the nasal cavity. The rootlets of the olfactory nerve pass through it.
Optic nerve :
The optic nerve is the second cranial nerve that connects the eye to the brain. The nerve transmits the visual impulses formed by the retina.
Optic canal :
The optic canal is a cylindrical canal running obliquely through the lesser wing of sphenoid bone near the base where it joins the body of sphenoid. It transmits the optic nerve and ophthalmic artery to the orbit.
The oculomotor nerve is the third cranial nerve. It enters the orbit via the superior orbital fissure and innervates the extrinsic muscles of the eye (except superior oblique and lateral rectus) that enable most movements of the eye and that raise the eyelid (levator palpebrae superioris).
The trochlear nerve is the fourth cranial nerve. It supplies the superior oblique muscle of the eyeball.
Ophthalmic, maxillary and mandibular divisions of trigeminal nerve :
The opthalmic, maxillary and mandibular are the three divisions of the trigeminal nerve (CN V). They are concerned mainly with the sensory innervation of the face. The ophthalmic and maxillary nerves are purely sensory in nature. The mandibular nerve is a mixed nerve and its motor component supplies the muscles of mastication.
Abducent nerve :
The abducent nerve is the sixth cranial nerve. It supplies the lateral rectus muscle of the eyeball.
Superior orbital fissure:
The superior orbital fissure is a cleft in the skull, lying between the lesser and greater wings of the sphenoid bone. It allows the passage of the following structures: - Oculomotor, trochlear and abducent nerves - Lacrimal, frontal and nasociliary branches of the ophthalmic nerve - Superior and inferior divisions of the ophthalmic vein
Foramen rotundum :
The foramen rotundum is a circular hole in the sphenoid bone that connects the middle cranial fossa and the pterygopalatine fossa. The maxillary nerve passes through it.
Foramen ovale :
The foramen ovale is situated in the posterior part of the sphenoid bone, posterolateral to the foramen rotundum. The mandibular nerve, accessory meningeal artery, lesser petrosal nerve and emissary veins pass through it.
The facial nerve is the seventh cranial nerve. It emerges from the pons. It controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue (via the chorda tympani nerve).
Vestibulocochlear nerve :
The vestibulocochlear nerve (also known as the auditory vestibular nerve) is the eighth cranial nerve. It transmits sound and the information of equilibrium (balance) from the inner ear to the brain
Internal acoutis meatus:
The internal auditory meatus is a canal within the petrous part of the temporal bone of the skull between the posterior cranial fossa and the inner ear. It transmits the facial and vestibulocochlear nerves and the labyrinthine artery.
The glossopharyngeal nerve is the ninth cranial nerve. It is a mixed nerve that exits the brainstem from the sides of the upper medulla, just anterior to the vagus nerve.
The vagus nerve is the tenth cranial nerve. It is concerned with the parasympathetic control of the heart, lungs, and digestive tract.
The Accessory nerve is the eleventh cranial nerve. It has two components: Cranial and spinal.
The cranial root of the accessory nerve emerges from the medulla, posterior to the olive as 4-6 rootlets. They fuse to form a single nerve and passes out of the posterior cranial fossa through the jugular foramen. It accompanies the vagus nerve and takes part in the formation of pharyngeal plexus.
The spinal root of the accessory nerve arises from the upper five segments of the spinal cord. It then ascends through the foramen magnum to enter the cranial cavity and unites with the cranial accessory nerve. It soon leaves the cranial cavity by passing through the jugular foramen and supplies two muscles in the neck: sternocleiodomastoid and trapezius.
Jugular foramen :
The jugular foramen is a large foramen in the base of the skull. It is located behind the carotid canal. It is bounded in front by the petrous portion of the temporal bone, and behind by the occipital bone. It is divided into three compartments and the structures passing through it are: - Inferior petrosal sinus in the anterior compartment - Ninth, tenth and eleventh cranial nerves in the intermediate compartment - Sigmoid sinus that continues as the internal jugular vein in the posterior compartment
Hypoglossal nerve :
The hypoglossal nerve is the twelfth cranial nerve. It is purely a motor nerve that innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve.
Hypoglossal canal :
The hypoglossal canal or the anterior condylar canal is a foramen in the occipital bone of the skull. The hypoglossal nerve passes through the canal.