HNNS Anatomy - Ear

Question 1

Blood supply, Nerve and Lymphatic supply of External ear.

Answer 1

Blood = Posterior auricular a. + Superficial temporal a./ External jugular vein

Nerve = Auriculotemporal nerve (v3) + CN7 + CN10

Lymph = superficial cervical LN (along EJV)

Question 2

Structure of external ear.

Answer 2

Outer 1/3 = cartilage

Innfer 2/3 = Temporal bone

Question 3

Anterior and posterior connection of the middle ear. Medial and lateral connection?

Answer 3

Anterior = Auditory tube and nasopharynx

Posterior = mastoid antrum + mastoid air cells

Medial = inner ear (cochlea + semicircular canal)

Lateral = external acoustic meatus

Question 4

List ossicle bones and connection for impedance matching.

Answer 4

Malleus
Incus
Stapes

Malleus = attached to tympanic membrane 
Stapes = attached to Small fenestra vestibuli

Question 5

List the vital structures on the medial wall of the tympanic cavity?

Answer 5

• Promontory + tympanic plexus + Lesser petrosal nerve
• Geniculate ganglion + facial nerve + Chorda tympani
• Fenestra cochleae + Fenestra vestibuli

Question 6

Name the muscle that attaches to the malleus.

Answer 6

Tensor tympani muscle at anterior wall of tympanic cavity

Question 7

List 2 muscles that open the eustachian tube.

Answer 7

Tensor veli palatini and Levator veli palatini

Question 8

Describe the opening of the auditory tube at the anterior wall of the tympanic cavity.

Answer 8

Cartilage superiorly and posteriorly = Tubal Eminence

Question 9

Muscle at the posterior wall of tympanic cavity?

Answer 9

Stapedius: attached to pyramid (bony spike) at posterior wall&raquo_space; neck of stapes ossicle bone

Question 10

Define location of Mastoid antrum

Answer 10

Petrous part of temporal bone

Below posterior cranial fossa

Question 11

Clinical significance of stylomastoid foramen at posterior wall of tympanic cavity?

Answer 11

Facial nerve exits here, very superficial at birth

Prone to damage in Assisted Forceps Delivery

Question 12

2 muscles for middle ear reflex.

Answer 12

Stapedius (CN7) 
Tensor tympani (V3)

Question 13

Name and location of roof of tympanic cavity?

Answer 13

Name = tegmen tympani

Location = Below middle cranial fossa and temporal bone

Question 14

List 2 important features beneath the floor of tympanic cavity.

Answer 14

Carotid canal (anterior to floor) + Internal carotid artery 
Jugular foramen ( postero-inferior) + Internal Jugular vein

Question 15

Landmark for surgical drainage of mastoid antrum by drilling.

Answer 15

Suprameatal triangle

Above and posterior to external acoustic meatus

Question 16

Structure of Auditory tube.

Answer 16

Anteromedial 2/3 = cartilage, mucosa = respiratory epithelium, lots of mucous glands
Postero-lateral 1/3 = Petrous temporal bone

Question 17

Arterial supply of auditory tube?

Answer 17

Ascending pharyngeal arteries + Middle meningeal arteries (through foramen spinosum)

Question 18

Venous drainage of auditory tube.

Answer 18

Pterygoid venous plexus

Question 19

Function of eustachian tube opening?

Answer 19

Air inside always absorbed by blood vessels

Soft palate elevation = open tube = air in pharynx replace absorbed air

Question 20

Middle ear A/V/N Lymph supply?

Answer 20

CN9&raquo_space; tympanic plexus
ECA
Perygoid plexus
Superior cervical LN

Question 21

Function of mastoid antrum.

Answer 21

Regulate temp. and pressure of middle ear

Question 22

Route of spread of otitis media to cranial fossa?

Answer 22

Through thin roof - Tegmen tympani

Erode through bone to middle cranial fossa

Question 23

Trace the course of CN9 through tympanic cavity to supply parotid gland.

Answer 23

Enter at floor via Tympanic canaliculus 
>> Tympanic plexus at medial wall 
>> Lesser petrosal nerve to Anterior wall 
>> Foramen ovale 
>> Otic ganglion 
>> Auriculotemporal nerve 
>> Parotid gland

Question 24

Trace the course of CN7 through tympanic cavity to supply Ant. 2/3 tongue sepcial sensory.

Answer 24

Facial nerve through Internal acoustic meatus
» Geniculate ganglion at medial wall
» Chorda tympani route through Posterior + Anterior wall
» Lingual nerve (V3)
» Ant 2/ tongue

Question 25

Trace the course of CN7 to form vidian nerve at pterygoid canal.

Answer 25

Medial wall of tympanic cavity 
>> CN7 >> Greater petrosal nerve 
>> Foramen lacerum*
>> Join with Deep petrosal nerve 
>> vidian nerve