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