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
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
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
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
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 (all in lateral wall)and VI which runs through the sinus with the ICA
The annular ring is the common origin of which 4 extraocular muscles? Which structures pass through the annular ring?
Common origin of the superior, middle, inferior and lateral rectus muscles
- Passing through the annular ring is the optic nerve & ophthalmic artery
- Superior division of the oculomotor nerve
- Nasociliary branch CN V1
- Inferior division of the oculomotor nerve
- Abducent nerve
What are the extracranial divisions of the facial nerve? WHat muscles does the facial nerve innervate?
Extracranial -
- Posterior auricular innervating occipitalis, posterior belly of digastric and stylohyoid
- Muscles of facial expresssion innervated by temporal, zygomatic, buccal, marginal mandibular and cervical branches
Intracranial - Stapedius innervated by the stapedial nerve
Facial nerve gives parasympathetic secretomotor fibres on the greater petrosal nerve to the lacrimal gland and on the chorda tympani nerve to the submandibular/sublingual salviary glands (as well as special sensory on this nerve)
- Describe how the facial nerve provides parasympathetic secretomotor innervation to the lacrimal gland?
- Facial nerve gives the greater petrosal nerve
- It joins with the deep petrosal nerve (sympathetic) to form the nerve of the pterygoid canal which synapses in pterygopalatine ganglion
- Postganglionic fibres then travel on the zygomatic branch of CN V2 to reach the lacrimal nerve which carries these fibres to the lacrimal gland
Describe how the facial nerve provides parasympathetic secretomotor innervation to the submandibular and sublingual glands?
- Chorda tympani exits the skull via the petrotympanic fissure to enter the infratemporal fossa
- The fibres hitch a ride on the lingual nerve (CN V3) to synapse in submandibular ganglion
- Postganglionic fibres supply the submandibular/subingual glands and special sensory taste fibres to the anterior 2/3rds of the tongue
The cochlear part of CN VIII is involved in hearing Where do fibres go once reaching the cochlear nuclei?
Once fibres reach the cochlear nuclei, they travel through the pons to the inferior colliculi in the mdibrain where they synapse before travelling to the medial geniculate nucleus of the thalamus
Fibres will then travel to the primary auditory cortex in the temporal lobe
What does the glossophryngeal nerve supply? (discuss motor on this card)
CN IX supplies motor innervation to: Pharyngeal plexus and stylopharyngeus (longitduinal muscle of the pharynx)
Describe how CN IX supplies parasympathetic secretomotor to the parotid gland?
- CN IX exits the skull via the jugular foramen.
- It will give a tympanic branch which will travel to tympanic cavity to form the tympanic plexus.
- From here, the lesser petrosal nerve, will emerge and will travel through the foramen ovale to synapse in the otic ganglion.
- Postganglionic fibres will then hitch a ride on the auriculotemporal nerve to reach the parotid gland.
What does the vagus nerve supply parasympathetic innervation to? What does it supply sensory to?
Vagus nerve supplies parasympathetic innervation to thoracic and abdominal viscera
- Sensory to dura (carries C2,3 fibres to posterior cranial fossa), ear, external auditory canal, lower pharynx, laryngeal mucosa, thoracic and abdominal viscera
Where are the pressure receptor and chemorecptor centres of the vagus nerve found?
- Pressure receptors found in the aortic arch
- Chemoreceptors found in the para-aortic body
Where does the spinal accessory nerve originate? How does it enter and exit the skull? What does the cranial root innervate?
The spinal accoessry nerve originates in the spinal cord and enters the foramen magnum to join the cranial root and both then exit the skull via the jugular foramen The cranial root then joins the vagus nerve to innervate the soft palate
What does the spinal accessory nerve innervate?
CN XI innervates the trapezius and sternocleidomastoid
Where does the hypoglossal nerve enter the root of the tongue? What does it innervate?
The hypoglossal nerve enters the root of the tongue above the hyoid bone It innervates all the intrinsic muscles of the tongue and all the extrinsic muscles (except palatogolossus which is innervated by the vagus nerve)
