Normal ear

Question 1

What is the function of the ear

Answer 1

Question 2

Explain the structure of the mammalian ear

Answer 2

Question 3

What are the types of cartilage in the external ear?

Answer 3

Auricular cartilage - forms anthelix (medially) and tragus (laterally) and conchal tube
Annular cartilage - fits within base of conchal tube ligamentous attachments to bony acoustic process of temporal bone
Scutiform cartilage - not part of ear canal, provides additional support

Question 4

Label the cartilages of the inner ear

Answer 4

Question 5

Describe the vascular supply to the external ear

Answer 5

Question 6

Describe the innervation of the external ear

Answer 6

Question 8

Describe the integumentary covering of the external inner

Answer 8

Epidermis: thin, stratified squamous keratinising epidermis (also over tympanic membrane)
Dermis: thin, contains hair follicles, sebaceous glands distally, apocrine (ceruminous) glands proximally

Question 9

Label this canine ear canal

Answer 9

Question 10

Describe the composition of cerumen/ear wax

Answer 10

Exfoliated cells
Sebaceous secretions (high lipid content)
Ceruminous gland secretions (more aqueous)
Immunoglobulins

Question 11

What is the function of cerumen/ear wax?

Answer 11

provides a protective and antimicrobial layer

Question 12

How do epithelial cells contribute to the cerumen/ear wax?

Answer 12

Epithelial cells from centre of TM travel to periphery, then desquamate
This helps transport cerumen to superficial portion of ear canal

Question 13

Describe the structure of the tympanic membrane

Answer 13

Stratified squamous keratinising epithelium laterally
thin lamina propria (collagen bundles)
simple squamous/cuboidal mucosal epithelium medially

Question 14

Label the tympanic membrane

Answer 14

Question 15

Describe the visible parts of the tympanic membrane and their function

Answer 15

Pars flaccida - accomodates changes in pressure
Pars tensa - transmits sound
Manubrium of malleus

Question 16

Label the tympanic membrane

Answer 16

Question 17

What are the compartments of the middle ear?

Answer 17

Epitympanum - contains malleus and incus
Mesotympanum - stapes attached to oval window - round window and opening to auditory tube
Hypotympanum/fundus - tympanic cavity

Question 18

What is the auditory/eustachian tube?

Answer 18

link between middle ear and back of throat

Question 19

Label the canine middle ear

Answer 19

Question 20

What do feline middle ears have that canines do not?

Answer 20

Incomplete bony septum across tympanic cavity

Question 21

Label the auditory ossicles

Answer 21

Question 22

Describe the anatomy of the eustachian tube

Answer 22

pseudostratified, ciliated, columnar epithelium
Scattered goblet cells

Question 23

Which nerves from in/close to the wall of the tympanic bulla?

Answer 23

Facial nerve
Branches of facial and vagus nerves form tympanic nerve
post-ganglionic fibres of cervical sympathetic trunk

Question 25

What are the sections of the inner ear?

Answer 25

Cochlea
Vestibule
Semicircular canals
Enceased in bony labrinth of petrous temporal bone

Question 26

What are the functions of the inner ear?

Answer 26

Hearing
Balance
Position and rotation of head in relation to gravitational forces

Question 27

What are the normal commensals found in the inner ear?

Answer 27

staphylococci
malassezia pachydermatis yeast

Question 28

What are otitis externa, media and interna?

Answer 28