Sem 2 - V - Cranial fossae & cranial nerves - Anterior/middle/posterior cranial fossa, cavernous sinus, annular ring, cranial nerves Flashcards
What is the anterior attachment of the falx cerebri?
Anteriorly, the falx cerebri attaches to the crista galli (superior projection of the perpendicular plate of the ethmoid bone)

In the anterior cranial fossa, we have the cribriform plate of the ethmoid bone What cranial nerve travels through this foramen?
The olfactory nerve fibres travels through the cribriform plate of the ethmoid bone to enter the olfactory bulb in the anterior cranial fossa

The optic canal, superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum, carotid canal are all found in the middle cranial fossa
- What passes through each of these?
- Label the foramina, start with black box, end with blue

- Optic canal - CN II and ophthalmic artery
- Superior orbital fissure - CN III, CN IV, CN V1, CN VI
- Foramen rotundum - CN V2 (black)
- Foramen ovale - CN V3 (red)
- Foramen spinosum -middle meningeal artery (green)
- Foramen lcaerum - ICA through superior part (blue)
- Carotid canal - ICA

Describe the route of the ICA as it enters the skull to the circle of willis?

The ICA will pass in the carotid canal (in the petrous temporal bone) to enter the skull It will emerge next to the foramen lacerum where it will run in the upper parts of the foramen lacerum as it heads towards the cavernous venous sinuses lateral to the sella turcicia It turns back on itself to enter the circle of willis

There is a groove between the temporal and occipital bones
- What is this groove for?
Foramina in posterior cranial fossa
- * Internal acoustic meatus
- * Jugular foramen
- * Hypoglossal canal
- * Foramen magnum
What passes through these?
This groove is for the sigmoid dural venous isinus on its way to the jugular foramen
- Internal acoustic meatus - CN VII and CN VIII
- Jugular foramen - CN IX, X, XI (descending)
- Hypoglossal canal - CN XII
- Foramen magnum - Medulla, meninges, vertebral arteries, CN XI (ascending) etc

What are the 12 cranial nerves?
Which are sensory, which are motor, which carry parasympathetic fibres?
- * Oh Oh Oh To Touch And Feel Virgin Girls Vaginas So Hot
- * Some Say Money Matters But My Brother Says Big Boobs Matter Most
- * 1973
- Olfactory - S
- Optic - S
- Oculomotor -M (carries parasympathetics)
- Trochlear - M
- Trigeminal - B
- Abuducent - M
- Facial - B (carries parasympathetics)
- Vestibulocochlear - S
- Glossopharyngeal - B (carries parasympathetics)
- Vagus - B (carries parasympathetics)
- Spinal accessory - M
- Hypoglossal - M

Where is the cavernous sinus located? What passes through the cavernous sinus?
Cavernous sinus is located on the greater wing of the sphenoid bone
Contains CN III, IV, V1, V2 and VI which runs through the sinus with the ICA

What is the only sensory system that does not synapse in thalamus before reaching the cortex?
Olfaction - smell
How do the olfactory nerves enter the skull? and how does it travel to the primary olfactory cortex? Where is the primary olfactory cortex?
The olfactory nerves originate in the olfactory mucosa and pass through the cribriform plate of the ethmoid bone to synapse in the olfactory bulbs
The olfactory tracts then travel back from the bulbs to reach the primary olfactory cortex located in the prepirifirom area of amygdala

The olfactory nerves are described as being an extension of the telencephalon (secondary vesicle) What are the optic nerves described as?
The optic nerves are described as being an extension of the diencephalon (secondary vesicle)

Where does the optic nerve begin? What % of fibres travel through the thalamus?
The optic nerves begin at the retina of the eye and travel back through the optic canal and meet at the optic chiasm
The chiasm continues as the optic tracts where 90% of fibres head towards the lateral geniculate nucleus of the thalamus 10% of the fibres travel along the medial root (non-geniculate) for unconscious regulation
Once the fibres reach the lateral geniculate nucleus, what are the optic fibres known as that head towards the primary visual cortex? Where is the primary visual cortex?
The optic tracts continue after the lateral geniculate nucleus as the optic radiation which heads towards the primary visual cortex located in the striate area of the occipital lobe

What is the ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit? It is the common origin of which 4 extraocular muscles?
The annular ring is a ring of fibrous tissue surrounding the optic nerve at its entrance at the opex of the orbit
Common origin of the superior, medial, inferior and lateral rectus muscles
- Levator palpebrae superioris, superior oblique and inferior oblqiue do not arise fromt he annular ring
Which structures pass through the annular ring?
- Optic nerve and ophthalmic artery together
- Superior division of oculomotor nerve
- Nasociliary branch of the ophthalmic nerve (CN V1)
- Inferior division of oculomotor nerve
- Abducent nerve

Where does the oculomotor nerve arise? What aspect of the cavernous sinus does it travel through? and how does it enter the orbit?
The oculomotor nerve arises from the midbrain and travels through the lateral wall of the cavernous sinus before passing through the superior orbital fissure to enter the orbit
The oculomotor nerve carries somatic motor and parasympathetic (viscercal efferent) fibres Which divisions of the nerve supply what?
- The superior division supplies motor innervation to the levator palpebrae superioris and superior rectus
- The inferior division carries parasympathetic fibres to the sphincter pupillae and the ciliary muscles as well as motor inenrvation to the medial rectus, inferior rectus and inferior oblique muscles

Where does the trochlear nerve arise and how does it reach the orbit? Does it pass through the annular ring?
The trochlear nerve arises from the posterior aspect of the midbrain and runs in the lateral wall of the cavernous sinus through the superior orbital fissure to enter the orbit
It travels superiorly to the annular ring
What is special about the trochlear nerve? What does the trochlear nerve innervate?
- The trochlear nerve is the only cranial nerve in which all the fibres cross to the opposite side of the nucleus (in brainstem)
- It is the only cranial nerve which arises from the posterior surface of the midbrain and it has the longest intracranial route of the cranial nerves
- Provides motor innervation to superior oblique muscle

Where does the trigeminal nerve originate from? What foramen do its 3 divisions pass through and to enter where?
Trigeminal nerve originates from the pons, forms a ganglion and divides into 3 divisions
- Ophthalmic division (CN V1) - passes through the superior orbital fissure to reach the orbit
- Maxillary division (CN V2) - passes through the foramen rotundum to reach the pterygopalatine fossa
- Mandibular division (CN V3) - passes through the foramen ovale to reach the infratemporal fossa
What branches from the 3 divisions of the trigeminal nerve allow for the passage of parasympathetic fibres?
Which divisions of the trigeminal nerve run in the lateral wall of the cavernous dural venous sinus?
Carries parasympathetic fibres from facial nerve
- Lacrimal (CN V1),
- Zygomatic (CN V2)
- Lingual (CN V3)
Carries parasympathetic fibres from glossopharyngeal nerve
- Auriculotemporal (CN V3)
CN V1 and CN V2 run in the lateral wall of cavernous dural venous sinus

Which division of CN V provides motor innervation to muscles? State the muscles
The mandibular division of CN V CN V3) proides motor innervation to the muscles of mastication
- * Medial pterygoid (nerve gives branches to tensor tympani and tensor veli palatini)
- * Lateral pterygoid
- * Masseter
- * Temporalis
- * Mylohyoid (nerve gives branches to the anterior belly of digastric)
State the sensory innervation supplied by each trigeminal nerve division
- CN V1 - general sensory to lacrimal gland, eyebrow, forehead, bridge of nose
- CN V2 - general sensory to skin of cheek, lower eyelid, ala of nose, upper jaw, lip and teeth, mucosa of mouth
- CN V3 - general sensory to lower lip and teeth, ear canal, partoid gland, mandible

Where does the abducent nerve originate and what foramina does it pass through? What does it travel through on its way to the orbit?
Abudcent nerve originates from the pons and passes in the middle of the cavernous sinus with the ICA and through the superior orbital fissure to enter the orbit
Does the abducent nerve pass through the annular ring and what muscle does it innervate?
Abducent nerve passes through the annular ring and innervates motor to the lateral rectus muscle













