Cranial Fossae and Cranial Nerves Flashcards
1
Q
What bony projections form the anterior cranial fossa
A
- Frontal bone anteriorly
- Ethmoid bone in the middle
- Body and lesser wings of the sphenoid bone posteriorly
2
Q
Name the 3 large depressions of the cranial base
A
- Anterior cranial fossa
- Middle cranial fossa
- Posterior cranial fossa
3
Q
What section of the brain is found in the anterior cranial fossa
A
The frontal lobes
4
Q
What does the anterior cranial fossa form
A
- Roof of the orbit
- Contributes to the nasal cavities
- Foramina related to the special senses of vision and smell (olfaction)
5
Q
What is the crista galli
A
A bony ridge formed by the frontal bone that provides attachment for the dura mater
6
Q
What structure related to the orbit does the sphenoid bone house
A
The optic canals
7
Q
What does the sphenoid bone form in the middle cranial fossa
A
- The floor of the middle cranial fossa
2. Orbital fissures
8
Q
Name the orbital fissures
A
- Foramen rotundum
- Foramen ovale
- Foramen spinosum
9
Q
What does the trigeminal nerve form in the middle cranial fossa
A
A large ganglion that sits on the floor and divides into its 3 divisions:
- Ophthalmic
- Maxillary
- Mandibular
10
Q
Where does CNV1 exit the cranial fossa, and what travels with it
A
Through the superior orbital fissure along with:
- CN III (oculomotor)
- CN IV (trochlear)
- CN VI (abducent)
11
Q
What foramen does the CNV2 division pass through
A
Foramen rotundum to pass towards the maxilla
12
Q
What foramen does the CNV3 division pass through
A
Foramen ovale to the infratemporal fossa, along with:
- Otic ganglion
- Accessory meningeal artery
- Lesser petrosal nerve
- Emissary veins
13
Q
What does the foramen spinosum carry
A
Middle meningeal artery, a branch of the maxillary artery that supplies the dura
14
Q
What is the foramen lacerum
A
A ragged hole that lies posterolateral to the hypophysial fossa; it is an artifact of a dried cranium
15
Q
What passes through the foramen lacerum
A
It allows the internal carotid artery to enter the middle cranial fossa
16
Q
What lobes of the brain sit in the middle cranial fossa
A
The temporal lobes
17
Q
What parts of the brain does the posterior cranial fossa house
A
- Cerebellum
- Pons
- Medulla oblongata
18
Q
What bone forms the majority of the floor of the posterior cranial fossa
A
The temporal bone
19
Q
What important passageways does the posterior cranial fossa border
A
- Foramen magnum
- Jugular foramina
- Hypoglossal canals
20
Q
What structures exit through the jugular foramina
A
- Internal jugular vein
- Glossopharyngeal nerve
- Vagus nerve
- Accessory nerve
21
Q
What structures enter the skull through the foramen magnum
A
- Vertebral arteries
2. Spinal part of the accessory nerves
22
Q
What structures exit the skull through the foramen magnum
A
- Start of the spinal cord
2. Meninges
23
Q
Where is the internal acoustic meatus located
A
Sitting in the petrous part of the temporal bone
24
Q
What structures exit the cranial cavity through the internal acoustic meatus
A
The structures enter the temporal bone:
- Facial nerve
- Vestibulocochlear nerve
25
Name the 12 cranial nerves (in order)
1. Olfactory
2. Optic
3. Oculomotor
4. Trochlear
5. Trigeminal
6. Abducent
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. Spinal accessory
12. Hypoglossal
26
What does the trigeminal nerve form before it divides into its divisions
A ganglion before it branches into its 3 divisions:
1. Ophthalmic
2. Maxillary
3. Mandibular
27
Describe what the olfactory nerve is, and what its pathway is
An outgrowth of the telencephalon (forebrain), and passes from the olfactory mucosa through the cribriform plate to synapse in the olfactory bulb
28
What is special about the olfactory nerve
It is the only sensory system not relayed through the thalamus
29
What is the optic nerve, and what does it provide
An extension of the diencephalon (forebrain) and it provides the special sense of vision
30
Describe the pathway of the optic nerve
From the retina through the optic canal, form chiasm then optic tracts (pass information to other areas of the brain, e.g. thalamus)
31
What is the oculomotor nerve, and what does it provide
Arises from the midbrain and plays an important role in the:
1. Innervation of the extraocular muscles
2. Changes in the shape of the lens and pupil
32
Describe the pathway of the nerve fibres of the oculomotor nerve
Along the lateral wall of the cavernous dural sinus, through the annular ring, and exit via the superior orbital fissure
33
Name the muscles that receive motor innervation from the oculomotor nerve
1. Superior levator palpebrae
2. Superior rectus
3. Inferior rectus
4. Medial rectus
5. Inferior oblique
34
Name the muscles that receive parasympathetic innervation from the oculomotor nerve
1. Sphincter pupillae
| 2. Ciliary muscles
35
Where does the trochlear nerve originate from, and what does it provide
From the midbrain, and provides motor fibres to one extraocular muscle: superior oblique
36
Describe the pathway of the trochlear nerve
Runs in the lateral wall of the cavernous dural sinus, outside the annular ring, and passes through the superior orbital fissure
37
What is special about the trochlear nerve
It is the only CN from the posterior surface of the midbrain - longest dural route
38
Where does the trigeminal nerve originate from, and what does it divide into
From the pons, forms a ganglion, and divides into 3 divisions:
1. Ophthalmic (enters the orbit through the superior orbital fissure)
2. Maxillary (enters pterygopalatine fossa through the foramen retundum)
3. Mandibular (enters the inferior surface of the skull through the foramen ovale)
39
What nerves (of the trigeminal nerve) allow passage of parasympathetic fibres
1. Lacrimal (CNV1)
2. Zygomatic (CNV2)
3. Auriculotemporal (CNV3)
40
Describe the distribution of innervation of CNV1
General sensation for the:
1. Eye
2. Lacrimal gland
3. Eyebrow
4. Skin of forehead
5. Nose
41
Describe the distribution of innervation of CNV2
General sensation for the:
1. Skin of the cheek
2. Lower lid
3. Upper jaw (and teeth)
4. Side of nose
5. Mucosa of mouth
42
Describe the distribution of innervation of CNV3
General sensation for the:
1. Ear canal
2. Parotid gland
3. Lower jaw (and teeth)
4. Anterior 2/3rd of the tongue
Motor to:
1. Muscles of mastication
2. Anterior belly of the digastric
3. Mylohyoid
4. Tensor tympani
5. Veli tensor palatini
43
Where does the abducent nerve originate from, and what does it provide
From the pons, and provides motor innervation to one extraocular muscle: the lateral rectus
44
Describe the pathway of the abducent nerve
Runs in the middle of the cavernous dural venous sinus (with the internal carotid), through the annular ring, and through the superior orbital fissure
45
Where does the facial nerve originate from, and describe its original pathway
From the pons, it exits through the internal acoustic meatus into the temporal bone
46
Describe the distribution of motor innervation of the facial nerve
1. Stapedius (in the temporal bone)
2. Muscles of facial expression (through 5 branches)
3. Stylohyoid
4. Posterior belly of the digastric
47
Name the 5 branches of the facial nerve that supply the muscles of the facial expression
1. Temporal
2. Zygomatic
3. Buccal
4. Mandibular
5. Cervical posterior auricular
48
Describe the distribution of sensory innervation of the facial nerve
Special sensation:
1. From the anterior 2/3rds of the tongue and palate
General sensation:
1. Skin of both aspects of the auricle
49
What glands receive parasympathetic innervation from the facial nerve
1. Submandibular salivary
2. Sublingual salivary
3. Lacrimal
4. Glands of the nose and palate
50
Describe the pathway of the vestibulocochlear nerve
From the vestibular and acoustic apparatus through the internal auditory meatus to the pons and medulla oblongata
51
Where does the vestibular sensation of the vestibulocochlear nerve arise from
The semicircular ducts, the utricle, and saccule; related to movement and balance
52
Describe the pathway of the cochlear nerve
From the inferior colliculi and medial geniculate nucleus of the thalamus to the auditory cortex; related to hearing
53
Where does the glossopharyngeal nerve originate from, and pass through
From the medulla oblongata and passes through the jugular foramen
54
Describe the distribution of the parasympathetic innervation of the glossopharyngeal nerve
The following glands:
1. Parotid
2. Labial
3. Buccal
55
Describe the distribution of the sensory innervation of the glossopharyngeal nerve
Special sensory:
1. Posterior 1/3rd of the tongue
General sensory:
1. Posterior 1/3rd of the tongue
2. Soft palate (gag reflex)
3. Pharynx
4. Tympanic cavity and membrane
5. Auditory tube
6. External ear and auditory canal
56
Describe the distribution of the motor innervation of the glossopharyngeal nerve
1. Pharyngeal plexus
| 2. Stylopharangeus muscle
57
Where does the vagus nerve originate from, and pass through
From the medulla (myelencephalon) and passes through the jugular foramen
58
Describe the distribution of the motor innervation of the vagus nerve
1. Pharyngeal plexus
2. Soft palate
3. Larynx (through the recurrent laryngeal)
59
Describe the distribution of the sensory innervation of the vagus nerve
1. Dura (postcranial fossa)
2. Ear
3. External auditory canal
4. Lower pharynx
5. Laryngeal mucosa
6. Thoracic and abdominal viscera
60
Describe the distribution of the parasympathetic innervation of the vagus nerve
The entirety of the gut tube until 2/3rds of the way along the transverse colon (when the sacral plexus takes over)
61
What plexi do the parasympathetic fibres of the vagus nerve join
1. Oesophageal
2. Cardiac
3. Bronchi
62
Where does the accessory nerve originate from, and pass through
The spinal cord then enters the foramen magnum and joins the 'cranial root' to pass through the jugular foramen
63
Describe the distribution of the motor innervation of the accessory nerve
1. Trapezius
| 2. Sternocleidomastoid
64
Where does the hypoglossal nerve originate from, and pass through
From the medulla oblongata (myelencephalon; anterior to the olives) and passes through the hypoglossal canal
65
Where does the hypoglossal nerve enter the route of the tongue
Above the hyoid bone
66
Describe the distribution of the motor innervation of the hypoglossal nerve
1. All intrinsic muscles of the tongue
| 2. All extrinsic muscles of the tongue, except palatoglossus (vagus nerve in the pharyngeal plexus)
