Osteology of the Base of the Skull, Orbit and Ear (Neuro)

Question 1

What are the small holes called in the Cranial fossae? What do they allow to pass through?

Answer 1

1. Cranial Foramina
2. Nerves, arteries and veins

Question 2

What are the three parts make up the base of the skull collectively and individually? What joins the bones of the skull together?

Answer 2

1. Cranial fossae
2. Anterior, Middle and Posterior cranial fossa
3. Joined together via fibrous joints known as sutures

Question 3

What rests in the Anterior cranial fossa? Parts of which three bones make up the Anterior cranial fossa

Answer 3

1. Frontal lobe
2. Parts of the Frontal lobe, Ethmoid bone and Sphenoid bone

Question 4

Which part of the frontal bone is found in the anterior cranial fossa? Which two parts of the Ethmoid bone are found in the Anterior cranial fossa?

Answer 4

1. Orbital part
2. Crista Galli and Cribriform plate

Question 5

What is the structure and function of the Cribriform plate? What is the Crista galli structure? What bone are they a part of?

Answer 5

Cribriform plate- multiple small holes allowing passing of olfactory nerves
Crista Galli- Vertical protrusion of cribriform plate
Ethmoid bone

Question 6

Which part of the Sphenoid bone makes up the anterior cranial fossa?

Answer 6

Lesser wings of the Sphenoid bone.

Question 7

What are the three structures of the Sphenoid bone?

Answer 7

1. lesser superior wings
2. Central body
3. Larger Inferior wings

Question 8

Which Parts of which two bones form the Middle Cranial Fossa?

Answer 8

1. Petrous and squamous parts of the Temporal bone
2. Greater wing and body of Sphenoid bone

Question 9

What is the structure of the petrous and squamous parts of the temporal bone respectively? What is located in the Petrous part?

Answer 9

1. Petrous- Very hard and bulbous inferior and medial part
2. Squamous- Flat lateral part of temporal bone
   Middle and inner ear located in petrous part

Question 10

What Important cavity does the body of the sphenoid bone contain? What does the cavity contain?

Answer 10

Pituitary fossa/ Sella turcica

Question 11

Which Foramen is this? What passes through it?

Answer 11

Optic canal
Optic nerve (to bony orbit)

Question 12

What structure is this? What passes through it?

Answer 12

1. Superior orbital fissure
2. Nerves that provide motor innervation (oculomotor, trochlear and abducens) and sensation (ophthalmic branch of trigeminal nerve) to orbital region

Question 13

What Foramen is this? What passes through it?

Answer 13

Foramen Ovale
Mandibular branch of Trigeminal nerve

Question 14

Which Foramen is this? What passes through it?

Answer 14

Foramen Spinosum
Middle meningeal artery

Question 15

What foramen is this? What passes through it?

Answer 15

Foramen Lacerum
Internal carotid artery

Question 16

What foramen is this? What passes through it?

Answer 16

Foramen Rotundum
Maxillary branch of trigeminal nerve

Question 17

Name the foramen a-d

Answer 17

a- Foramen Spinosum
b- Foramen Ovale
c- Foramen Rotundum
d- Superior Orbital Fissure

Question 18

Name the Foramen e-h

Answer 18

e-Optic canal
f- Cribriform plate
g- Foramen Lacerum
h- Internal auditory meatus

Question 19

Name the foramen i-k

Answer 19

i- Jugular foramen
j-Hypoglossal canal
k- Foramen Magnum

Question 20

What three structures rest in the posterior cranial fossa? What bone primarily makes up this fossa? Which part makes up a small part of the fossa??

Answer 20

1. Occipital lobe, Cerebellum and Brainstem
2. Occipital bone
3. Small part of the petrous part of temporal bone

Question 21

Which four foramen are in the posterior cranial fossa?

Answer 21

1. Internal auditory meatus
2. Jugular foramen
3. Hypoglossal canal
4. Foramen Magnum

Question 22

Which foramen is the largest? What passes through it?

Answer 22

Foramen magnum
allows the CNS to become the spinal cord

Question 23

Which small foramen is found next to the foramen magnum? What passes through it?

Answer 23

Hypoglossal canal
Hypoglossal nerve

Question 24

Which foramen is found in between the hypoglossal canal and internal auditory meatus? What passes through it (4)?

Answer 24

Jugular foramen
Glossopharyngeal, Vagus and accessory nerves and internal jugular vein

Question 25

What passes through the Internal auditory meatus? Into where?

Answer 25

Vestibulochlear and facial nerves into the inner ear cavity

Question 26

What are four consequences of skull fractures?

Answer 26

1. Brain itself directly damaged 2. Damage structures passing through foramina 3. Dura and arachnoid meninges damaged 3. Significant bleeding

Question 27

What is the temple also known as? Why is it weak? What structure lies deep to it?

Answer 27

Pterion 4 bones converge at it Middle meningeal artery

Question 28

What is it called when the sutures of the skull completely fuse before a child is two?

Answer 28

Craniosynostosis

Question 29

Which is the shape of the bony orbits? What 6 bones make up the bony orbit?

Answer 29

1. cone shaped 2. Frontal, Sphenoid, Zygomatic, Maxillary, Ethmoid and Lacrimal

Question 30

What are 5 structures found in the orbits?

Answer 30

1. Eye 2. Extraocular muscles 3. Nerves 4. Fat 5. Lacrimal gland

Question 31

What are the 7 Extraocular muscles of the bony orbit?

Answer 31

1. Levator palpebrae superioris 2. Superior rectus 3. Inferior rectus 4. Medial rectus 5. Lateral rectus 6. Superior oblique 7. Inferior oblique

Question 32

What are the functions of the Superior rectus, Inferior rectus, Medial rectus and Lateral rectus respectively?

Answer 32

1. elevate and adduct eye 2. Depress and adduct eye 3. Adduct eye (look medially) 4. Abduct eye

Question 33

What nerves supply the Lateral rectus muscle, Superior oblique and other 5 extraocular muscles respectively? Acronym to remember?

Answer 33

1. CN 6- Abducens nerve 2. CN 4- Trochlear nerve 3. CN 3- Oculomotor nerve LR6SO4 (Lateral rectus 6 Superior oblique 4)

Question 34

What is the function of the Levator palpebrae superioris, Inferior oblique and superior oblique nerves respectively?

Answer 34

1. elevate superior eyelid 2. Extort, depress and abduct eye 3. Intort, Elevate and Abduct eye

Question 35

What do Extorsion and Intorsion mean?

Answer 35

Extorsion- rotate top of eye laterally Intorsion- rotate top of eye medially

Question 36

Where do the four recti extraocular muscles originate from?

Answer 36

Back of the orbit on a fibrous ring known as common tendinous ring

Question 37

Why do the superior and inferior rectus muscles cause the eye to also intort, extort or adduct?

Answer 37

They are not parallel to one another and at an angle

Question 38

Where does the superior oblique muscle originate from? Where in the orbit is this located? Where does it insert in the eye? What does the contraction cause?

Answer 38

Originates at a fibrous sling called the trochlea Located in the superior and mediall corner of the orbit Muscle inserts onto top of eye Intorsion

Question 39

Where does the Inferior oblique muscle originate from? What direction does it pull the bottom and top of eye? What is this called?

Answer 39

1. Originates from medial orbital wall (inserting on bottom of eye) 2. Pulls bottoms of eye medially and top laterally 3. Extorsion

Question 40

Why does the eye need oblique muscles?

Answer 40

To counteract the secondary effects of intorsion and extorsion caused by the inferior and superior recti muscles

Question 41

What does accommodation mean in the eye? What type of lens' are more useful for long and short distance sight and why?

Answer 41

Focusing varying amounts of light depending on how far away the object is. Long distance- thinner lens as less refraction of light Short distance- thicker lens as more retraction of light

Question 42

What muscles are responsible for adjusting thickness of the lens? What fibres are they made up of from which nerve?

Answer 42

Ciliary muscles Parasympathetic fibres from the oculomotor nerve (CN 3)

Question 43

What is the function of the pupil? What muscle and nerve cause it to constrict?

Answer 43

Protect retina from over-exposure to light Constrictor pupillae (in iris) controlled by oculomotor nerve (CN 3)

Question 44

What muscle and nerve fibres cause the pupils to dilate?

Answer 44

Dilator pupillae and sympathetic fibres from the sympathetic chain

Question 45

What is the Pupillary light reflex? What Afferent nerve is involved and where does it carry information to and from?

Answer 45

Automatic adjustment of the amount of light entering the eye. Optic nerve carries information from the retina to the midbrain

Question 46

What is the name of the synapse where the afferent nerve meets the efferent nerve? What is the name of the efferent nerve? Where does it travel to? (In the pupillary light reflex pathway)

Answer 46

1. Edinger-Westphal nucleus 2. Oculomotor nerve 3. Constrictor pupillae muscle

Question 47

When a light is shone in the eye of a healthy patient why do both of the pupils constrict?

Answer 47

There is Connection between the right and left Edinger-Westphal nuclei meaning when one side is activated both sides are activated

Question 48

Which structure is responsible for producing tears and where is it located? What nerve innervates this structure?

Answer 48

Lacrimal gland Located in the superior and lateral corner of the orbit Innervated by parasympathetic fibers from the facial nerve (CN 7 )

Question 49

What direction do tears flow across the eye and where do they drain into?

Answer 49

Tears flow medially and inferiorly and drain into lacrimal ducts which enter the nasal cavity via the nasolacrimal duct.

Question 50

Name a, b and c

Answer 50

a- Pinna b- Ear canal c- Tympanic membrane

Question 51

Where do sound waves travel from the Pinna? Why is the Pinna shaped the way it is?

Answer 51

Down the Ear canal and to the tympanic membrane (eardrum) which vibrates like a drum transmitting the soundwaves to the cochlea.

Question 52

What cavity is behind the Tympanic membrane? What are the three bones that are present called? What is their function?

Answer 52

Middle ear cavity 3 Ossicles carry sound waves to the oval window which conveys it into the cochlea

Question 53

What are the three ossicles called?

Answer 53

1.Malleus 2.Incus 3.Stapes

Question 54

Where does the handle of the malleus rest against and where does the head connect to?

Answer 54

Handle rests on Tympanic membrane head connects to the Incus

Question 55

Where does the Stapes bone transmit sound waves to and from? What does the structure sound travels to do?

Answer 55

From the Incus to the oval window Oval window- marks the boundary of the middle and inner ear cavities.

Question 56

Where is the superior opening of the auditory tube? Where is the inferior opening of the auditory tube? What is the function of the Auditory tube?

Answer 56

Superior- middle ear cavity Inferior- posterior and inferior part of nasal cavity Connection is to maintain equal air pressure.

Question 57

Why is the auditory tube important when the outside pressure changes?

Answer 57

Pressure increases on Tympanic membrane. Air passes through the auditory tube to increase air pressure on the inside of the tympanic membrane.

Question 58

What muscle increases tension in the tympanic membrane? What bone does it insert on? What does this do? Which nerve supplies this muscle?

Answer 58

Tensor tympani Malleus Reduces how much tympanic membrane can vibrate Mandibular branch of Trigeminal nerve (CN 5)

Question 59

Which muscle dampens the vibrations of the stapes? What nerve supplies it?

Answer 59

Stapedius muscle Facial nerve (CN 7)

Question 60

What is the network of small bony passages within the petrous part of the temporal bone called?

Answer 60

Bony labyrinth

Question 61

Two main organs within the Inner ear cavity?

Answer 61

Cochlea and Vestibular system

Question 62

What is the structure and function of the cochlea?

Answer 62

Fluid filled cavity in inner ear Sound waves travel through the flyid=w

Question 63

Which part of the cochlear do sound waves first enter? What is in contact with this?

Answer 63

Oval window Stapes

Question 64

What is the other opening from the middle ear to the inner ear called? What does it do?

Answer 64

Round window Bulges in and out to allow fluid within the cochlea to move

Question 65

What three structures does the Vestibular system contain?

Answer 65

Semicircular canals Utricle Saccule

Question 66

What are the functions of the three structures in the Vestibular system?

Answer 66

SCC- allow us to perceive movement Utricle and Saccule- Perceive linear acceleration

Question 67

What in the Vestibular system allows us to perceive movement? How does it do this?

Answer 67

Fluid Movement of fluid is detected by specialised cells

Question 68

When Movement is perceived by specialist nerves where are impulses sent to (three structures)?

Answer 68

Cerebellum, Thalamus and certain cranial nuclei

Question 69

What nerve carries impulses from the cochlea and vestibular system? Through where? Where is the nuclei of this nerve located?

Answer 69

Vestibulocochlear (CN 8) Through the auditory meatus (to the CN8 nucleus) Nuclei is in the Pons

Question 70

What is Oculocephalic reflex? How does this occur? (involves three other cells)

Answer 70

Maintaining a fixed gaze whilst moving our head Vestibulocochlear nuclei has connections to other brainstem nuclei including Oculomotor, trochlear and abducens

Question 71

What is Vertigo?

Answer 71

Symptom of being able to perceive movement when there isn't any (dizziness)

Question 72

What is the name for a benign tumour surrounding the Vestibulocochlear nerve?

Answer 72

Vestibular Schwannoma

Question 73

What is the term known as the inflammation within the middle ear cavity?

Answer 73

Ottis Media