Middle Ear

Question 1

where is the middle ear?

Answer 1

within the temporal bone

Question 2

where does the middle ear extend from and to?

Answer 2

from tympanic membrane to the lateral wall of the inner ear

Question 3

what is the main function of the middle ear?

Answer 3

transmits vibrations from the tympanic membrane to the inner ear via auditory ossicles

Question 4

what two parts can the middle ear be divided into?

Answer 4

• tympanic cavity
• epitympanic cavity

Question 5

what does the tympanic cavity contain?

Answer 5

auditory ossicles - malleus, incus and stapes

Question 6

what are the 3 auditory ossicles? list from largest to smallest

Answer 6

malleus, incus, stapes

Question 7

what is the role of the auditory ossicles?

Answer 7

transmit sound vibrations through the middle ear

Question 8

how do the auditory ossicles work?

Answer 8

• sound vibrations causes tympanic membrane to move/oscillate
• causes auditory ossicles to move

Question 9

how does the malleus attach to the tympanic membrane?

Answer 9

via the handle of malleus

Question 10

what do the two limbs on the incus attach to?

Answer 10

short limb - posterior wall of middle ear
long limb - joins to stapes

Question 11

what does the base of the stapes attach to?

Answer 11

oval window of inner ear

Question 12

describe how the auditory ossicles attach to each other:

Answer 12

• handle of malleus attaches malleus to tympanic membrane
• head of malleus articulates with incus in epitympanic recess
• long limb of incus articulates with stapes
• base of stapes joins the oval window of the inner ear

Question 13

what cells are located posterior to the epitympanic recess?

Answer 13

mastoid air cells - found in mastoid process of temporal bone

Question 14

what is the role of the mastoid air cells?

Answer 14

• “buffer system of air”
• release air into tympanic cavity when the pressure is too low

Question 15

what connects the mastoid antrum (cavity that contains the mastoid air cells) with the middle ear?

Answer 15

aditus to mastoid antrum

Question 16

what two muscles serve a protective function in the middle ear?

Answer 16

tensor tympani
stapedius

Question 17

what is the acoustic reflex?

Answer 17

• tensor tympani and stapedius contract in response to loud noise
• inhibits vibrations of auditory ossicles
• reduces transmission of sound to inner ear

Question 18

where does the tensor tympani originate and attach?

Answer 18

originates from auditory tube
attaches to handle of malleus

Question 19

how does the tensor tympani pull the handle of malleus what contracting?

Answer 19

pulls it medially

Question 20

what is tensor tympani innervated by?

Answer 20

tensor tympani nerve - branch of mandibular

Question 21

where does the stapedius muscle attach?

Answer 21

stapes

Question 22

what is the stapedius muscle innervated by?

Answer 22

facial nerve

Question 23

what is the auditory/eustachian tube?

Answer 23

a cartilaginous and bony tube that connects the middle ear to the nasopharynx

Question 24

what is the role of the auditory tube?

Answer 24

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

Question 25

which wall of the nasopharynx does the auditory tube open into?

Answer 25

lateral wall

Question 26

why do middle ear infections tend to be more common in children than adults?

Answer 26

tube is shorter and straighter in children than in adults

Question 27

what is the pathology of otitis media with effusion/"glue ear"?

Answer 27

* persistant dysfunction of the auditory tube causes a negative pressure to develop in the middle ear * draws out transudate from muscose of middle ear * causes infection

Question 28

how will the eardrum appear in a pt with otitis media with effusion?

Answer 28

inverted, wiht visible fluid inside the ear

Question 29

what is mastoiditis?

Answer 29

middle ear infection spreads to mastoid air cells

Question 30

what is a potentially fatal consequence of mastoiditis?

Answer 30

infection can spread to middle cranial fossa and cause meningitis

Question 31

Label this diagram showing the mastkid air cells

Answer 31

Question 32

Label the bones of the middle ear

Answer 32

Question 33

Label this diagram of the middle ear

Answer 33

Question 34

Label the muscles of the inner ear

Answer 34