Ear anatomy

Question 1

What is the function of the auricle?

Answer 1

Collect, focus, and direct sound down the funnel-shaped external acoustic meatus to the tympanic membrane

Question 2

What antibodies have been identified in cerumen?

Answer 2

IgA, IgG and IgM

Question 3

What is the predominant immunoglobulin in normal and inflamed ears?

Answer 3

IgG for both

Question 4

What is the function of the Eustachian (auditory) tube?

Answer 4

Equalize pressure on both sides of the tympanic membrane

Question 5

Name the 2 structures that attach to the malleus

Answer 5

Tympanic membrane and incus

Question 6

Name the 3 components of the middle ear

Answer 6

Tympanic cavity, 3 auditory ossicles and tympanic membrane

Question 7

What 2 structures attach to the stapes?

Answer 7

Vestibular window (in contact with perilymph fluid) and incus

Question 8

Where does the tensor tympani muscle insert?

Answer 8

Malleus

Question 9

What nerve innervates the tensor tympani muscle?

Answer 9

Branch of trigeminal nerve

Question 10

Where does stapedius muscle insert?

Answer 10

Stapes

Question 11

What nerve innervates the stapedius muscle?

Answer 11

Stapedial branch of facial nerve

Question 12

Where do both the tensor tympani and stapedius muscles originate?

Answer 12

Tympanic bulla

Question 13

Name the bony structure that houses the cochea

Answer 13

Promontory (where cochlear and vestibular windows are located)

Question 14

Describe the 3 layers of the tympanic membrane and their origin

Answer 14

Inner epithelium: originates from pharyngeal pouch

Central layer: fibrous connective tissue of pharyngeal wall

Outer layer: stratified squamous epithelium derived from ectoderm of first pharyngeal groove

Question 15

What is the stria mallearis?

Answer 15

Outline of the manibrium of malleus

Question 16

Where should a myringotomy be performed?

Answer 16

Caudal ventral quadrant of TM (pars tensa)

Question 17

Which direction does the manubrium of the malleus face?

Answer 17

C-shaped and concave aspect of the C points rostrally

Question 18

Where and in what direction does tympanic membrane regenerate?

Answer 18

Radially from the umbo pars tensa

Question 19

Name the clinical signs of Horner’s syndrome

Answer 19

Ptosis, pupillary miosis, prominent third eyelid, enopthalmia

Question 20

Where does the annular cartilage insert?

Answer 20

Within the bone of external acoustic meatus

Question 21

What are the 3 parts of the tympanic cavity?

Answer 21

Dorsal: smallest

Middle (aka tympanic cavity proper): adjacent to TM

Ventral: largest; tympanic bulla with septum bulla

Question 22

Know how to label this

Question 23

What are the 2 divisions of the septum bulla in cats?

Answer 23

Pars tympanica: small and dorsolateral

Pars endotympanica: large and ventromedial

Question 24

Name another dog breed reported to have PSOM other than CKCS?

Answer 24

Boxer, dachshund, and shih tzu

Question 25

Name the anatomical region where one inserts the ototscopic cone?

Answer 25

Antitragus

Question 26

What dog breed typically have excessive compound hair follicles in the horizontal ear canal?

Answer 26

Cocker spaniel dogs

Question 27

What dog breeds have simple hair follicles in the horizontal ear canals?

Answer 27

Greyhounds and mixed breed dogs

Question 28

What are simple coiled tubular glands that resemble apocrine sweat glands?

Answer 28

Ceruminous glands

Question 29

Ceruminous glands are composed of an inner secretory layer surrounded by ______ cells on a basement membrane

Answer 29

Myoepithelial cells

Question 30

What is the normal pH of ear canal epithelium in dogs? A. 4.6-7.2 B. 6.0-7.4 C. 5.2-7.2 D. None of the above

Answer 30

A. 4.6-7.2 -- Normal B. 6.0-7.4 -- Chronic otitis C. 5.2-7.2 -- Acute otitis

Question 31

What is the gas in the middle ear composed of?

Answer 31

Nitrogen 83%, oxygen 12%, carbon dioxide 4.7%

Question 32

What is an acoustic reflex?

Answer 32

When the ear is stimulated with a VERY loud sound, the stapedius muscle will contract to protect the middle ear from damaging level of noise

Question 33

Acoustic reflex is usually absent in patients with what disease?

Answer 33

Middle ear disease

Question 34

Blood supply to the ear comes from what 2 main arteries?

Answer 34

External carotid artery and vertebral arteries

Question 35

What is the largest artery to the ear?

Answer 35

Intermediate auricular branch

Question 36

Name the 4 nerves of the sensory innervation of the pinna

Answer 36

Trigeminal, facial, vagus, second cervical

Question 37

Which cartilage does NOT contribute to the formation of the externa ear? A. Auricular cartilage B. Annular cartilage C. Scutiform cartilage D. None of the above

Answer 37

C. Scutiform cartilage

Question 38

Know how to label this

Question 39

Can you label the inner and external ear structures of the dog?

Answer 39

You better!

Question 40

What nerve innervates the rostroauricular and caudoauricular muscles of the pinna?

Answer 40

Motor branches of the facial nerve

Question 41

What does the external ear consist of?

Answer 41

The auricle (pinna) and external acoustic meatus

Question 42

What does the middle ear consist of?

Answer 42

The ossicles, tympanic cavity, and bulla

Question 43

What does the inner ear consist of?

Answer 43

Cochlea and semicircular canals

Question 44

In horses, how is the junction between the cartilaginous and osseous portions of the external acoustic meatus grossly identified?

Answer 44

An abrupt change from pigmented to nonpigmented epithelium.

Question 45

Match the Tympanic membranes: Pig, Goat, Horse, Dog (ignore the bottom 2 images)

Answer 45

A, Horse. In the horse, the tympanic membrane (tympanum) is more round than other species. The manubrium of the malleus forms a very shallow arc and is centrally located in the tympanum. B, Dog. The tympanum is oval to comma-shaped, and the manubrium of the malleus is C-shaped. C, Pig. Similar to the dog, but the manubrium of the malleus is shorter and straighter. D, Goat. Ruminants tend to have a more triangular-shaped tympanic membrane. In both pigs and ruminants, the manubrium of the malleus is more rostral and medial than in other species.