The External and Middle Ear Flashcards by Brian McCalister

Innervation of the auricle? -4

-greater auricular,
-lesser occipital
Facial CN7 branches
Vagus CN10 branches

How well did you know this?

Not at all

Perfectly

Why can cleaning your ears sometimes cause you to cough?

Can stimulate the auricular branch of the vagus nerve Vagus nerve is responsible for the cough reflex

How well did you know this?

Not at all

Perfectly

Vasculature of the auricle? -2

Posterior auricular,

superficial temporal

How well did you know this?

Not at all

Perfectly

What is the external acoustic meatus?

Sigmoid shaped tube extending from the deep part of the concha to the tympanic membrane

How well did you know this?

Not at all

Perfectly

What gives the external acoustic meatus structure?

Cartilage from the auricle + Bony support from the temporal bone

How well did you know this?

Not at all

Perfectly

Innervation of the external acoustic meatus? -2

Mandibular CN5B3
Vagus CN10

How well did you know this?

Not at all

Perfectly

Describe the direction that the external acoustic meatus travels

Initially superioanterior Then superioposterior Then inferioanterior

How well did you know this?

Not at all

Perfectly

What are the 3 layers of the tympanic membrane?

Outside = skin
Core = Connective tissue
Inside = Mucous membrane

How well did you know this?

Not at all

Perfectly

What is the tympanic membrane connected to?

Surrounding temporal bone by a fibrocartilaginous ring

How well did you know this?

Not at all

Perfectly

How is the malleus attached to the tympanic membrane?

The handle of malleus attaches at the umbo and Continues superiorly

How well did you know this?

Not at all

Perfectly

What are the parts of the membrane moving away from the tympanic membrane called? -2

Anterior and posterior mallear folds

How well did you know this?

Not at all

Perfectly

What is an auricular hematoma?

blood collection between cartilage and overlying perichondrium usually as a result of trauma

How well did you know this?

Not at all

Perfectly

What can an auricular haematoma lead to and how?

Accumulation of blood disrupts the vascular blood supply to the cartilage of the pinna so if not drained quickly, can –> cauliflower ear

How well did you know this?

Not at all

Perfectly

Main causes of tympanic membrane perforation - 2

Trauma
Otitis media (purulent fluid build up –> rupture)

How well did you know this?

Not at all

Perfectly

Function of the auricle?

Captures and transmits sound to the external acoustic meatus

How well did you know this?

Not at all

Perfectly

Which bone does the middle ear lie within?

temporal bone

How well did you know this?

Not at all

Perfectly

Where does the middle ear extend from and to?

From the tympanic membrane to the lateral wall of the internal ear

How well did you know this?

Not at all

Perfectly

Purpose of the middle ear?

Transmit vibrations from the tympanic membrane to the inner ear via three bones

How well did you know this?

Not at all

Perfectly

Sections of the middle ear? -2

Tympanic cavity - medial to the tympanic membrane and contains majority of bones of the middle ear
EpiTympanic recess - superiorly, near mastoid air cells

How well did you know this?

Not at all

Perfectly

Borders of the middle ear?

Roof / Lateral / Floor / Medial / Posterior / Anterior

Visualised as a rectangular box

Roof: Petrous temporal bone

Lateral: TM and epitympanic recess

Floor: “Jugular Floor” Thin layer of bone separates it from internal jugular

Medial: lateral wall of inner ear

Posterior: “Mastoid Wall” A bony partition between the tympanic cavity and mastoid air cells. Hole in the partition superiorly allowing communication called the aditus to the mastoid antrum

Anterior: thin bony plate with two openings for the auditory tube and tensor tympani muscle. Separates mid ear from internal carotid

How well did you know this?

Not at all

Perfectly

What does the Middle Ear roof separate the middle ear from?

Middle cranial fossa

How well did you know this?

Not at all

Perfectly

What makes a bulge in the medial wall of the inner ear?

Facial CN7

How well did you know this?

Not at all

Perfectly

Names of the auditory ossicles? -3

MIS ossicle bones

Malleus

Incus

Stapes

How well did you know this?

Not at all

Perfectly

Where does the head of the malleus lie?

Epitympanic recess where it articulates with the incus

How well did you know this?

Not at all

Perfectly

What are the muscles called in the middle ear? -2

Tensor tympani and stapedius

Function of the muscles of the middle ear?

Contract in response to loud noise, inhibiting vibrations of the bones Reduces transmission of sound to the inner ear Called the acoustic reflex

Describe attachment of Middle ear muscles -2

1. Tensor tympani: from auditory tube to handle of malleus, pulling malleus medially 2. Stapedius: attaches to stapes

Innervation of the middle ear muscles? -2

Tensor tympani = [Mandibular CN5B3] Stapedius - Facial CN7

Where are the mastoid air cells located? What are they?

Posterior to the epitympanic recess within the [mastoid antrum cavity] of temporal bone; Collection of air-filled spaces

Function of the mastoid air cells?

Act as a buffer system - release air into the tympanic cavity when pressure is too low

How do the mastoid air cells communicate with the middle ear?

Aditus to middle antrum

What two things does the **EPAT** [**E**ustachian **P**haryngotympanic **A**uditory **T**ube] connect?

Mid ear to nasopharynx

Function of the **EPAT** *[Eustachian Pharyngotympanic Auditory Tube]*?

Equalizes pressure of middle ear to that of the external auditory meatus

What is cholesteatoma?

Growth of stratified squamous epithelium in the middle ear ## Footnote *Congenital vs Acquired*

What problems can cholesteatoma cause?

Damage bones of middle ear due to increase pressure & Releases osteolytic enzymes Patients present with hearing loss and sometimes facial nerve palsy

How to treat cholesteatoma?

Surgical removal

What is mastoiditis?

Otitis media can spread to the mastoid air cells, as its a good site for pathogenic replication

Complications of mastoiditis?

Mastoid process gets infected and can spread to middle cranial fossa causing meningitis

How is mastoiditis treated?

Pus is drained from air cells, careful of nearby facial nerve

What is glue ear?

Otitis media with effusion

How does otitis media with effusion occur?

*AKA Glue Ear* persistent dysfunction of EPAT (blockage, inflammation, genetic mutation) --\> inability to equalize middle ear pressure --\> negative pressure develops inside middle ear which draws out transudate from mucosa of the middle ear --\> Glue Ear infection *EPAT [Eustachian Pharyngotympanic Auditory Tube]*

Why are children more prone to infection? -2

EPAT is shorter and more horizontal ## Footnote *EPAT [Eustachian Pharyngotympanic Auditory Tube]*

Which opening does the Stapes Base articulate

OV (**O**val **V**estibular) window

Which opening does the Scala Tympani articulate

RC (**R**ound **C**ochlear) window

What role does the external ear play in hearing?

Collects sound

What role does the middle ear play in hearing?

Amplifies sound

What role does the inner ear play in hearing?

Transduces sounds

What is the speed of sound in air?

330m/s

Does sound travel faster or slower in water than air?

Faster

What frequencies should humans hear ?

20 - 20,000 Hz

What range of frequencies are tested on an audiogram?

250Hz to 6000Hz

What does the frequency of a sound wave do?

Dictates how high or low

What does the amplitude of a sound wave do?

Dictates loudness

In the middle ear, how is sound amplified?

Stapes hits against the oval window with greater force when vibrations are higher

What ligament suspends the stapes bone?

Annular ligament

What muscles are related to the stapes bone?

Stapedius Tensor tympani

What muscles open the Eustachian tube?

Tensor veli palatini Levator palatine

What manoeuvre can be done to equalise the ears?

Valsalva manoeuvre

What can cause glue ear to be more common?

Cleft palate which causes the muscles which open the eustachian tube to be dysfunctional

Through which window is sound waves transmitted?

Oval

What is the round window for?

Allows pressure to leave

Where is the sound actually perceived?

The fine hairs on the cochlea

What nerve transmits the sound vibrations to the brain?

Cochlear nerve

What bone is the inner ear located in?

Petrous part of the temporal bone

Where is perilymph?

Within the bony labyrinth

Where is the endolymph?

Within the membranous labyrinth

What makes up the membranous labyrinth?

3 semicircular ducts- anterior, posterior and lateral

What connects each semicircular duct to its base- the utricle?

The ampulla

What sensory organ is contained within the ampulla?

Cristae ampullaris

What happens when endolymph moves against the cristae ampullaris?

Hair cells become depolarised which sets up an action potential

What separates the endolymph and perilymph?

Basilar membrane

How does gentamicin cause tinnitus?

It causes damage to the outer hair cells

What is another name for stereo cilia?

Inner hair cells

What is meant by tonotopic organisation of the cochlea?

Different areas of the basilar membrane are responsible for different frequencies of sound

Where it the apex of the cochlea?

Furthest from the round window i.e. centre of spiral

What are the two otolith organs called?

Utricle Saccule

What structure is responsible for vertigo and what are they made of?

Otoconia Calcium carbonate crystals

What is special about the orientation of the semicircular canals?

They are orientated at 90 degrees to each other and are paired.

What causes deflection?

Movement of endolymph by bodily movement causes the stereocilia to deflect

What is spontaneous nystagmus?

Movement of the eye without a stimulus