11 - Head & Neck - The Eye 3 + The Ear

Question 1

How will the optic disc appear during fundoscopy if there is raised intracranial pressure?

Answer 1

Papilloedema = swelling of the optic nerve

- Optic disc = swollen with blurred margins

Question 2

How will the optic disc appear during fundoscopy if there is raised intra-ocular pressure?

Answer 2

Optic disc cupping

Question 3

What is optic disc cupping?

Answer 3

Increased diameter of central cup of optic nerve, due to increased intra-ocular pressue
* sign of glaucoma

Question 4

What is a Meibomian cyst? How is this different to a stye?

Answer 4

Blocked Meibomian gland within tarsal plate

Stye = blocked sebaceous gland at base of eyelash (infected hair follicle)

Question 5

Outline the consensual pupillary light reflex:

Answer 5

• Light shone in left eye
• Sensory afferent from L retina via CN II
• To Pretectal nucleus (brainstem)
• To BOTH L + R Edinger-Westphal nuclei
• Parasympathetic fibres hitchhike on CN III
• Innervate both sphincter pupillae
  = Both L + R pupils constrict

Question 6

What are the afferent and efferent nerves of the pupillary light reflex?

Answer 6

Afferent = CN II
Efferent = CN III

Question 7

Why might someone not be able to look up if they have a blow-out fracture?

Answer 7

Blow-out fracture = fractured floor of orbit

• Orbital fat can prolapse and ocular-muscles can become trapped
• Haematoma may form in inferior rectus
• Inferior rectus contracts in response to damage, preventing patient from looking up

Question 8

Why might someone with a blow-out fracture have reduced sensation over their cheek?

Answer 8

• Damage to the inferior orbital branch of CN V2

- -> Emerges below orbit via infra-orbital foramen

Question 9

What are the effects on lacrimation if orbicularis oculi is damaged?

Answer 9

• Inferior eyelid retracts, exposing cornea
• Cornea becomes dry and unprotected
• Constant corneal irritation increases lacrimal secretion
• Risk of ulceration

Question 10

Which nerve stimulates the lacrimal gland?

Answer 10

Parasympathetic fibres associated with CN VII

-> via Greater petrosal to pteygopalatine ganglion to gland

Question 11

How can thrombophlebitis of the facial veins spread into the cranial cavity?

Answer 11

Facial veins drain directly into internal jugular vein,

BUT have anastamoses with superior + inferior ophthalmic veins which drain into cavernous sinus

Question 12

What are the afferent and efferent nerves of the corneal blink reflex?

Answer 12

Afferent = CN V1 (Ophthalmic)
Efferent = CN VII

Question 13

How is visual acuity tested?

Answer 13

Snellen chart

Question 14

Name the 4 parts of the temporal bone:

Answer 14

• Squamous part
• Petromastoid part
• Tympanic plate
• Styloid process

Question 15

The external acoustic meatus lies within which part of the temporal bone?

Answer 15

Tympanic plate

Question 16

Describe the epithelium of the external acoustic meatus:

Answer 16

Keratinised squamous

- Cartilaginous outer 1/3rd = is lined with hairs + produces cerumen (+ dead cells = wax)

Question 17

When examining the ear, how should the pinna be manipulated for ideal view of the tympanic membrane?

Answer 17

Child = Down + back
Adult = UP, OUT + BACK

Question 18

The middle and inner ear lie in which part of the temporal bone?

Answer 18

Petromastoid part

Question 19

What is the function of the external ear?

Answer 19

Collect, transmits + focuses sound waves onto tympanic membrane

Question 20

What is the approx. length of the external acoustic meatus?

Answer 20

~ 2.5 cm long

Question 21

What is the approx. diameter of the tympanic membrane?

Answer 21

~ 1 cm

Question 22

Which nerve innervates the internal surface of the tympanic membrane?

Answer 22

CN IX

Question 23

What structures does the middle ear cavity communicate with anteriorly and posteriorly?

Answer 23

Ant = nasopharynx via eustachian tube
Post = Mastoid air cells

Question 24

Why is it important for the middle ear cavity to be connected to the nasopharynx?

Answer 24

• Allows equalisation of air pressure between middle ear + atmosphere
• Allows drainage + ventilation

Question 25

When is the Eustachian tube opened?

Answer 25

During swallowing

- opened due to pull of palate muscles

Question 26

Name the ossicles:

Answer 26

Malleus
Incus
Stapes

Question 27

Which ossicle is attached to the tympanic membrane?

Which ossicle articulates with the bony labyrinth of the inner ear (via oval window)?

Answer 27

Malleus

Stapes

Question 28

What is the function of the ossicles?

Answer 28

Amplify and concentrate sound energy from eardrum to oval window

Question 29

Which muscles reduce sound amplitude by resisting ossicle movement? Which nerves innervate them?

Answer 29

• Stapedius - CN VII

- Tensor tympani - CN V3

Question 30

The membranous labyrinth of the ear sits within the bony labyrinth. Name the fluid which separates these structures:

Answer 30

Perilymph

Question 31

Name the fluid contained within the membraneous labyrinth:

Answer 31

Endolymph

Question 32

Which organ lies within the cochlear, and is reponsible for hearing?

Answer 32

Spiral organ of Corti

Question 33

Describe the process of hearing:

Answer 33

• Sound waves are transmitted down the external ear, causing vibration of the tympanic membrane
• Vibration of the ossicles results in transmission of the sound waves to the oval window
• Causes wave motion of the endolymph within the membranous labyrinth
• Stimulates hair cells triggering AP in CN VIII > Brain