Unit 2: Ear Structure & Function

Question 1

What is the landmark for cytology and otoscope insertion?

Answer 1

intertragic incisure

Question 2

What are the cartilage types of the external ear?

Answer 2

Auricular (vertical canal) and annular (horizontal canal)

Question 3

How do the external canal cartilages interact with each other?

Answer 3

Auricular cartilage overlaps annular cartilage - allows for flexibility and movement

Question 4

Where does debris like to build up in the external canal?

Answer 4

In the little “dip” at the end of the vertical canal

Question 5

How can you keep dogs from jumping when using an otoscope?

(they jump from the scope hitting the fold)

Answer 5

Take the pinna and pull it out and away to get the scope under the fold easier

Question 6

What are the lengths of the auricular and annular cartilages?

Answer 6

Auricular = 4.1 cm

Annular = 1.2 cm

Question 7

What is the diameter of the external canal at thr tragus?

Answer 7

5.8 cm

Question 8

What is the mean pH of the ear canal in dogs?

Answer 8

6.1 in males, 6.2 in females

Question 9

What is the relative humidity of the external canal?

Answer 9

80%

Question 10

What is the temperature of the external canal?

Answer 10

0.6ºC lower than rectal

Question 11

What are the types of pinnae and which one has more otitis?

Answer 11

Erect vs. pendulous

Question 12

The volume of the ear canal impacts _____.

Answer 12

treatment

Question 13

The length of the ear canal impacts _____.

Answer 13

examinations

Question 14

What does the skin of the ear canal contain?

Answer 14

Sebaceous and apocrine (ceruminous) glands, hair follicles

Question 15

What types of inflammation/infection involve the structures of the skin of the canal?

Answer 15

Folliculitis, adenitis, ruptured sweat glands

Question 16

What is the technical term for ear wax?

Answer 16

cerumen

Question 17

What are the components of cerumen?

Answer 17

Secretions of sebaceous glands, ceruminous (apocrine) gland secretions, epithelial cells (keratinocytes)

Question 18

What is the lipid content of cerumen made of?

Answer 18

Margaric, oleic, stearic, and linoleic fatty acids

Question 19

What are the functions of cerumen?

Answer 19

Lubrication, hydration, protection

Question 20

Lipid content of cerumen decreases ___ to ___% in chronic otitis externa.

Answer 20

49%, 24%

Question 21

What can dilute lipid content of cerumen?

Answer 21

Hyperplasia of the apocrine glands

Question 22

What is the “self-cleansing” mechanism of the ear?

Answer 22

epithelial migration

Question 23

What can a prominent pars flaccida resemble in the ear canal?

Answer 23

Tumors - can use pneumo-otoscopy to test

Question 24

What is the point of pneumo-otoscopy?

Answer 24

Gentle blowing or use of a bulb to create positive pressure in the ear canal, making the pars flaccida move

Question 25

What are the smallest muscles in the body?

Answer 25

tensor tympani and stapedius

Question 26

What is the nerve bundle that runs thru the middle ear?

Answer 26

chordae tympani

Question 27

What is the smallest bone in the body?

Answer 27

stapes

Question 28

What cells line the middle ear side of the tympanic membrane?

Answer 28

VERY thin layer of cuboidal epithelium

Question 29

What cells line the ear canal side of the tympanic membrane?

Answer 29

Thin layer of stratified squamous epithelium

Question 30

What things live in between the 2 cell layers of the tympanic membrane?

Answer 30

Lymphatics, vessels, collagen

Question 31

What are some things in the cat ear that are different from the dog?

Answer 31

They have a bony septum that divides the middle ear into 2 compartments, their external canal doesn't have a deep "trap" like the dog's, and it is a smaller diameter (difficult to pass some scopes)

Question 32

How is the tympanic membrane of the cat different than the dog?

Answer 32

It is more transparent, the septum obstructs view, less hair visible

Question 33

T/F: The malleus of cats is straighter than the dog's.

Answer 33

True

Question 34

The middle ear is housed in the _____ bone.

Answer 34

temporal

Question 35

How many chambers does the middle ear have?

Answer 35

2

Question 36

What cavities are behind the ear drum?

Answer 36

Epitympanic, tympanic, ventral (fundic)

Question 37

What cells line the middle ear?

Answer 37

Modified respiratory epithelium (some ciliated and secretory cells)

Question 38

What other structures are in the middle ear?

Answer 38

Nerves, vessels, ossicles, muscles

Question 39

What are the 4 main components of the middle ear?

Answer 39

1. Ventral/fundic cavity (tympanic bulla) 2. Tympanic cavity proper 3. Epitympanic recess/cavity 4. Promontory

Question 40

What do striations on the tympanic membrane indicate?

Answer 40

That it is a super young dog

Question 41

What middle ear structures can be seen on otoscopic exam?

Answer 41

Ventral cavity, promontory, edge of bulla

Question 42

What does the stapes attach to?

Answer 42

vestibular window

Question 43

What general nerve types are found in the middle ear?

Answer 43

Parasympathetic and sympathetic

Question 44

A

Answer 44

malleus

Question 45

B

Answer 45

stapes

Question 46

C

Answer 46

vestibular window

Question 47

D

Answer 47

nerves

Question 48

What cranial nerve exits into the middle ear?

Answer 48

facial nerve

Question 49

What foramen does the facial nerve exit out of?

Answer 49

stylomastoid foramen

Question 50

What is the auditory tube?

Answer 50

Communication between the pharynx and the middle ear

Question 51

Where does the auditory tube enter?

Answer 51

Enters bulla at rostral end of middle ear

Question 52

What is the significance of the auditory tube?

Answer 52

It is a mjor pathway for entrance of infectioous agents

Question 53

Where is the cochlea contained?

Answer 53

Within the petrous temporal bone

Question 54

What are general pathologic changes that can happen in the ear?

Answer 54

Inflammation, glandular hyperplasia, epidermal hyperplasia, fibroplasia, ossification

Question 55

What can environmental changes lead to in otitis externa?

Answer 55

Increased temperature of ear canal, increased apocrine secretions (increased humidity, dilution of lipid content of wax), proliferation of micro-organisms

Question 56

Chronic, uncontrolled inflammation results in _____ changes.

Answer 56

progressive

Question 57

\_\_\_\_\_ hampers treatment!

Answer 57

fibrosis

Question 58

What is a key point to make with clients regarding diagnosis and management?

Answer 58

There is a need for aggressive diagnosis and management EARLY in the process

Question 59

What is the minimum treatment for folliculitis and furunculosis?

Answer 59

21-30 days

Question 60

What is adenitis?

Answer 60

Inflammation of the apocrine (ceruminous) glands

Question 61

Adenitis is present in all _____ otitis cases.

Answer 61

chronic

Question 62

What are the defense mechanisms of the ear?

Answer 62

Conformation, hair, cerumen, self-cleansing mechanism

Question 63

What are the 7 best practices in the management of otitis?

Answer 63

1. Use appropriate diagnostics 2. Prepare the canal for treatment 3. Choose treatment wisely 4. Medications must be administered properly 5. Use *quality control* to evaluate treatment 6. Consider long-term maintenance therapy 7. ID and control primary factors