Cranial nerves: origination + foramen
What cranial nerves are associated with the forebrain?
CN 0 (terminal) CN I (olfactory) CN II (optic) remember: forebrain = tel- and di-encephalon forebrain<cerebrum<lateral ventricles and 3rd ventricle
What cranial nerves are associated with the midbrain?
CN III (oculomotor) CN IV (trochlear) remember: midbrain = mesencephalon mesencephalon<mesencephalic aqueduct
What cranial nerves are associated with the hindbrain?
CN V (trigeminal) CN VI (abducent) CN VII (facial) CN VIII (vestibulocochlear) CN IX (glossopharyngeal) CN X (vagus) CN XI (accessory) CN XII (hypoglossal) remember: hindbrain = met- + myel-encephalon hindbrain<4th ventricle
which part(s) of the sphenoid complex does CN V go through?
CN V is the trigeminal nerve: opthalamic branch of CN V goes through the orbital fissure maxillary branch goes through rostral alar foramen/round foramen mandibular branch goes through the oval foramen all the foramen above are approx in the middle of the left side of the image
Incisive duct
Duct through which the vomeronasal organ connects to the roof of the mouth
What are the 5 main parts of the sphenoid bone complex?
From rostral to caudal: 1. Optic canal 2. Orbital fissure 3. Rostral alar foramen (hidden round foramen has an entry to it) 4. Caudal alar foramen 5. Oval foramen Note: the oval foramen can be separate from, or in association with, the caudal alar foramen
Which of the cranial nerves associated with the hindbrain are specifically associated with the medulla trapezoid body? Which to the base of the medulla/the cervical spinal cord?
Medulla Trapezoid Body (shown in green in the pic, the yellow area is the 4th ventricle cavity): CN VII (facial) CN VIII (vestibulocochlear) Medulla base/cervical spinal cord: CN XI (accessory)
Which of the cranial nerves associated with the forebrain are specifically associated with the olfactory bulbs? Which to the diencephalon?
Olfactory bulbs: CN 0 (terminal) CN I (olfactory) Diencephalon: CN II (optic)
Hypoglossal canal
caudal and ventral to tympano-occipital fissure
Tympano-occipital fissure
caudal to the tympanic bulla
Metencephalon
cerebellum and pons
Telencephalon
cerebrum (including olfactory bulbs)
Sphenoid complex
foramen (opening in bone) through which CN II through CN VI go through
5 major divisions arising from the 3 germ layers
going clockwise from the largest structure: 1. Telencephalon (forebrain) 2. Metencephalon (hindbrain) 3. Myelencephalon (hindbrain) 4. Mesencephalon (midbrain) 5. Diencephalon (forebrain)
CN XII foramen
hypoglossal canal of occipital bone
Foramen for CN VIII
internal acoustic meatus note: it is *internal* - does not exit the skull
How does the maxillary branch of CN V goes make it to the rostral alar foramen (through which it exits)?
it enters the caudal alar foramen alongside the maxillary vein and artery then it transverses the alar canal (rostrally) finally, it exits through the rostral alar foramen (alongside the maxillary vein and artery)
Functionally speaking, is the maxillary vein "seen" as a vein?
it is considered to be more for drainage of the eye
Stylomastoid foramen
located in the temporal bone just caudal to the external acoustic meatus of the dorsal tympanic bulla
Myelencephalon
medulla oblongata aka brain stem
Mesencephalon
midbrain - tectum and tegmentum
What is the location of the rostral + caudal alar foramen and the oval foramen?
near the caudal most end of the zygomatic arch note: the arch includes what is denoted as "ramus" as well as "zygomatic"
Which part of the sphenoid complex does CN II go through?
optic canal
Which part of the sphenoid complex does the CN VI go through?
orbital fissure
which part of the sphenoid complex does CN III go through?
orbital fissure
which part of the sphenoid complex does CN IV go through?
orbital fissure
Given that the cranial nerve number increases as you move from the forebrain to the hindbrain, they are numbered _____ to _____.
rostral to caudal (0 = most rostral) this also indicates that the cranial nerves exit the brain in order from rostral to caudal
Foramen for CN VII
stylomastoid foramen
Cribiform plate
superior surface of the ethmoid; perforated by a foramina which allows passage of CN 0 (terminal) and CN I (olfactory) which then enter the olfactory bulbs, providing a sense of smell
What definitive brain cavitie(s) are in the hindbrain?
the fourth ventricle remember, the hindbrain is composed of the: metencephalon (derived structures include the pons and cerebellum) and myelencephalon (derived structure includes the medulla oblongata) *the fourth ventricle is present in both the met and myelencephalon
What definitive brain cavitie(s) are in the forebrain?
the lateral ventricles and the third ventricle remember: forebrain is made of the telencephalon and diencephalon and the derived structures include the cerebrum, thalamus, hypothalamus, ...
What definitive brain cavitie(s) exist in the midbrain?
the mesencephalic aqueduct remember: the midbrain is composed of the mesencephalon and the derived brain structures include the tectum and tegmentum
Due to their location, CN 0 (terminal) nerves are also called the _______ nerves.
vomeronasal nerves (they extend from the vomeronasal organ)
Jugular foramen
where CN IX, X, and XI enter the skull
Occipital fissure
where CN IX, X, and XI exit the skull
