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BDS3 Anatomy Student 3 > Anatomy W11 - The ear > Flashcards

Anatomy W11 - The ear Flashcards

1
Q

What components make up the external ear?

A

The auricle/pinna
The external acoustic meatus

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2
Q

What is the function of the external ear?

A

Gathers sounds and channels/transmits it through the external acoustic meatus

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3
Q

What cartilage forms the auricle?

A

Elastic cartilage

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4
Q

What epithelium lines the external acoustic meatus?

A

Stratified squamous keratinised epithelium

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5
Q

What are they safety measures that prevent foreign bodies entering the ear?

A

Ceruminous glands that produce wax

Little hairs at the start of the external auditory meatus

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6
Q

What is a clinical problem of the external ear?
How do you treat this?

A

Otitis externa - bacterial infection of the external auditory meatus which causes inflammation.

flush the ear out and give antibiotics

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7
Q

What epithelium lines the middle ear?

A

Respiratory epithelium - pseudostratified columnar epithelium with goblet cells

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8
Q

What is the tympanic membrane? - Where is it located?

A

(Also known as the eardrum)

Located in the middle ear

It’s a thin, tense membrane that transmits sound vibrations from the external acoustic meatus to the ossicles of the middle ear

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9
Q

Name the components of the middle ear.

A

The tympanic membrane
The ossicles - inca, malleus, stapes
The auditory tube

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10
Q

What is the function of the auditory tube in the middle ear?

A

Allows air into the middle ear

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11
Q

Why does new air have to be let in to the middle ear via the auditory tube?

A

Since the lining of the middle are absorbs the air

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12
Q

Where is the opening of the auditory tube?

A

In the nasopharynx - surrounded by the tubal elevation/tonsils

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13
Q

Name the ossicles of the middle ear.

A

Malleus - Handle connects to the tympanic membrane

Inca (between the malleus and stapes)

Stapes - looks like a stirrup and faces into the cochlear/internal ear

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14
Q

What joint is present between the ossicles?

A

Synovial joints

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15
Q

What holds the ossicles in place?

A

Ligaments

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16
Q

What is the ligament that holds the stapes in place called?
What clinical problem can be associated with this ligament?

A

The annular ligament of the stapes

Cause of deafness in older people:
This ligament can calcify with age = restricts movement of the stapes = deafness

17
Q

What window does the stapes move in and out of?

A

The fenestra vestibuli / The oval window

18
Q

Describe how the lever system of the ossicles functions.

A

As sound moves down the external acoustic meatus it causes movement/vibration of the tympanic membrane.

The vibration of the tympanic membrane cause the stapes to move in and out of the fenestra vestibuli

Movement of the fenestra vestibuli causes movement of fluid within the inner ear/cochlea which is received by the stereocilia/hair cells and transmits impulses down the vestibulocohlear nerve.

19
Q

What is the function of the round window/fenestra cochleae?

A

Since fluid cannot be compressed within the inner ear/cochleae, when the stapes is in the fenestra vestibuli the fluid moves through the fenestra cochleae to compensate for this fluid movement.

20
Q

What clinical problem can be associated with the middle ear? Describe what can occur.

A

Otitis media - infection of the middle ear /
Chronic otitis media - if it persists for a long time

Can lead to breakdown of the tympanic membrane = pus leaking out into the external acoustic meatus

Can also spread to the mastoid air cells = difficult to treat

21
Q

What is the risk associated with a bad infection of the middle ear?

A

Facial palsy:
Since the bone separating the middle ear and the facial nerve is thin - infection can cause inflammation that applies presses to the facial nerve = palsy

22
Q

Why is otitis media common?

A

Since the middle ear communicates with the nasopharynx via the auditory tube - infection can spread from the pharynx to ear easily.

23
Q

What condition of the middle ear presents in young children around the age of starting school?

A

Chronic Otitis media with effusion

24
Q

If you had to look at the tympanic membrane of a child with chronic otitis media with effusion with an auriscope, what would you see?

A

An air bubble and straw coloured mucous

25
Q

What would a child with otitis media with effusion have in the lead up to diagnosis?

A

Series of sore throats

26
Q

Describe what occurs in chronic otitis media with effusion .

A

The sore throats cause hyertrophy/enlargement of tubal tonsils from the overgrowth of lymphoid tissue.

The enlarged tubal tonsils surrounding the auditory tube causes blockage.

New air cannot enter the middle ear

The blockage causes the goblet cells to proliferate and produce more mucous

Mucous accumulates within the ear and prevents the ossicles in the lever system from moving to generate sound = deafness.

27
Q

How is chronic otitis media with effusion treated? What happens if it doesn’t resolve?

A

No treatment - just monitor - should return to normal as the child grows

No resolution = grommet inserted into the tympanic membrane for a few weeks/months which allows new air to enter into the middle ear.

28
Q

What safety mechanisms are in place to protect the ossicles from loud noise?

A

There are muscles which are attached to the ligaments which hold the ossicles in place.

When there is a loud noise the stapedius muscle contracts reflexly via CN 7 to reduce movement of the ligament which holds the stapes in place.

When there is a loud noise the tensor tympani muscle contracts reflexly via mandibular div of CN 5 to reduce movement of the ligament which holds the handle of the malleus in place.

29
Q

What is the fucntion of the cochleae?

A

To translate the movements/vibrations of the fluid into electrical impulses

30
Q

What components are present within the inner ear?

A

The cochleae
The semicircular canals

31
Q

What is the function of the semicircular canals?

A

They allow you to maintain your balance when your eyes are focused on a point but your head is moving.

32
Q

What is the most common cause of deafness? Name the other causes.

A

Common - Wax build up in the external acoustic meatus

Calcified annular ligament of the stapes - old
Neurological causes
Chronic Otitis media with effusion - young children

33
Q

What nerve crosses over the tympanic membrane in the middle ear?

A

The chorda tympani - facial nerve

BDS3 Anatomy Student 3 (26 decks)

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