L16: Ear

Question 1

Divisions of ear

Answer 1

• External, middle (aka tympanic cavity) and inner ear

Question 2

Cartilage of ear auricle

Answer 2

• Elastic cartilage

Question 3

Parts and Function of auricle

Answer 3

• Collect sounds waves and pass them to ext auditory meatus - Helix - Anti-helix - Lobule - Tragus

Question 4

Parts of the external ear

Answer 4

• Auricle - External auditory meatus - Tympanic membrane

Question 5

Glands of external auditory meatus

Answer 5

• Ceruminous glands – produce cerumen

Question 6

Describe the external auditory meatus from a structural standpoint

Answer 6

• Lateral 1/3rd is cartilaginous - Medial 2/3rd is bony

Question 7

Nerve supply of external auditory meatus

Answer 7

• Auriculotemporal (CN V3) - Vagus nerve

Question 8

Blood supply to external acoustic meatus?

Answer 8

• Deep auricular branch of maxillary artery

Question 9

Coverings of TM

Answer 9

• Outside = skin - Inside = mucus membrane

Question 10

Central depression of TM – function?

Answer 10

• UMBO: attachment of handle of malleus

Question 11

Quadrants of TM

Answer 11

• Anterosuperior - Anteroinferior: contains cone of light - Posteroinferior - Postersuperior

Question 12

Which quadrant of the TM shows the cone of light?

Answer 12

• anteroinferior

Question 13

Nerve supply to TM

Answer 13

• Auriculotemporal (external surface) – from CN V3 - Tympanic branch of CN IX (internal surface)

Question 14

Structures of the middle ear/tympanic cavity?

Answer 14

• Opening of Eustachian (pharyngotympanic/auditory) tube - Ossicles (malleus, incus, stapes) - Tensor tympani m - Stapedius m - Oval and round windows - Tympanic plexus

Question 15

In what bone is the middle ear located?

Answer 15

• Petrous portion of temporal bone

Question 16

Explain divisions of tympanic cavity

Answer 16

• Roof: thin layer of temporal bone called tegmen tympani - Floor: above carotid canal and beginning of int jugular vein - Posterior wall: entrance to mastoid air cells and entrance of stapedius muscle and chorda tympani - Lateral wall: tympanic membrane - Medial wall: tympanic plexus, oval and round windows - Anterior wall: separation from carotid canal, has opening to Eustachian tube

Question 17

What is the tegmen tympani?

Answer 17

• roof of tympanic cavity formed by thin layer of temporal bone

Question 18

What CN forms the tympanic plexus?

Answer 18

• CN IX

Question 19

What structure does the stapes connect with on its medial side?

Answer 19

• Oval window

Question 20

What does the tensor tympani m attach to?

Answer 20

• Handle of malleus

Question 21

What does the stapedius m attach to?

Answer 21

• Neck of stapes

Question 22

Innvervation of tensor tympani and stapedius muscles?

Answer 22

• Tensor tympani: CN V3 - Stapedius: CN VII

Question 23

Two parts of inner ear

Answer 23

• Vestibular portion - Auditory portion

Question 24

Divisions of labyrinth/inner ear. Describe each

Answer 24

• 1.) Bony labyrinth: a.) Vestibule: oval cavity which communicates anteriorly with cochlea and posteriorly with semicircular canals b.) Cochlea: bony snail-like structure coiled 2.25 times around pillar known as modiolus c.) Semicircular canals: three of these forms 2/3 of a circle and communicate with vestibule - 2.) Membranous labyrinth: membranous duct system located in bony labyrinth, contains endolymph. Consists of cochlear duct, three semicircular ducts and two sacs called utricle and saccule

Question 25

Function of tensor tympani and stapedius muscles?

Answer 25

• Dampen vibration of ossicles