Theme 8a

Question 1

3 Sections of the Ear

What are they?

What does each consist of?

What ois the role of each?

Answer 1

External Ear: funnels air vibrations towards tympanic membrane

• External auditory meatus
• Tympanic Membrane

Middle Ear: conducts vibrations from tympanic membrane to inner ear

• Tympanic cavity
• Pharyngotympanic tube
• Ossicles & muscles
  
  • Air-filled

Inner Ear: Hearing & Balance

• Bony labyrinth
• Membranous labyrinth

Question 2

What are the two parts of the Temporal Bone?

What does each part consist off?

Answer 2

Petromastoid part: Tympanic ring

Squamous part:

• Styloid process
• Jugular Foramen – Transmits Internal Jugular Vein, CN IX, X and XI
• Carotid Canal
• Stylomastoid Foramen – Transmits CNVII (after emerging through Internal Auditory Meatus)
• Internal Auditory Meatus – Transmits CN VII and VIII
• Greater Petrosal Hiatus – Transmits Greater Petrosal Nerve of CNVII
• Lesser Petrosal Hiatus – Transmits Lesser Petrosal Nerve of CNIX

Question 3

Inner ear

What are the two divisions of the inner ear?

What fluid does division contain?

Answer 3

• Bony labryinth - perilymph
• Membranous Labyrinth - endolymph

Question 4

Facial Nerve

Where does it enter and leave?

What are gthe branches?

Answer 4

In: through the internal auditory meatus in the petrous temporal bone

Out: stylomastoid foramen where it pierces parotid gland & the five facial branches

Branches:

• Greater Petrosal Nerve: arises from the geniculate ganglion into middle cranial fossa, through Fo. Lacerum, into Pterygoid Canal to ~+ deep petrosal nerve = N of Pterygoid Canal and then joining Pterygopalatine Ganglion
• N to Stapedius
• Chorda Tympani: enters the middle ear across the tympanic membrane, enters the infratemporal fossa via petrotympanic fissure where it joins lingual nerve to go to submandibular ganglion
• Lesser Petrosal Nerve:
• aves tympanic plexus IX to join V otic ganglion via ovale

Question 5

Lesions of the Facial Nerve

1. What aspcts of the Facial Nerve Function can be tested?
2. Where can lesions be present?

Answer 5

1.

• Lacrimation (pterygopalatine ganglion)
• Stapedius Reflex
• Taste (chorda tympani)

2.

Taste only = between N to Stapedius & Chorda Tympani

S.R. & Taste = between Geniculate ganglion & N to Stapedius