Anatomy of the Ear

Question 1

• What are the parts of the auricle ?
• What is the blood supply/innervation to the auricle?

Answer 1

• Auricle components
  
  • Helix
  • Antihelix
  • Tragus
  • Antitragus
  • Lobule
  • Concha
• Blood Supply
  
  • Posterior auricular and superficial temporal as
• Nerve supply
  
  • Greater auricular n
  • Auriculotemporal n
  • Vagus n (CN X)
  • Facial N (CN VII)

Question 2

• Where do auricular hematomas occur?

Answer 2

• Between perichondrium and cartilage
• Can stimulate abnormal collagen growth and lead to Cauliflower ear if left untreated

Question 3

• The external acoustic meatus extends from _ of the auricle to the _ membrane
• Lateral 1/3 is made of _
• Medial 2/3 is made of _
• A child’s external aucostic meatus is _ than an adults
• Lateral 1/3 is _ shaped (pulled superiorly, posteriorly and laterally during otoscopic exam)

Answer 3

• Concha to tympanic membrane
• Cartilage
• Bone
• Shorter
• S shaped

Question 4

• Otitis externa

Answer 4

• Infection of external acoustic meatus
• Risk factors:
  
  • Excessive moisture
  • Trauma
  • Devices that occlude ear canal
  • Dermatologic conditions
  • Prior radiation therapy

Question 5

• When performing an otoscopic examination of the ear, the reflected cone of light is always _ and _ in relation to the rest of the tympanic membrane

Answer 5

• Anterior and inferior

Question 6

• The most vascular portion of the tympanic membrane is the _ aspect

Answer 6

• Superior

Question 7

• Epitympanic recess

Answer 7

• Where malleus and incus heads are located (protected by bone)

Question 8

• Otitis media

Answer 8

• Inflammation of the middle ear
• Inflammation and swelling of mucous membrane of tympanic cavity may block pharyngotympanic tube (aka Eustachian tube)
• Tympanic membrane is red and bulges

Question 9

Effusion means _

Answer 9

• Full of fluid

Question 10

• Tympanostomy tube placement

Answer 10

1. Maringotomy-incision to open TM (usually done on posterior-inferior aspect of TM-less vascular)
2. After maringotomy, drain fluid
3. Then can perform tympanostomy-place tube in incision from maringotomy (tubes can fall out or be taken out at later time)

Question 11

• What makes up the roof of the middle ear cavity?
• The roof separates the middle ear from what?

Answer 11

• Tegmen tympani (bone)
• Middle cranial fossa

Question 12

• What makes up the floor of the middle ear cavity?
• This separates the middle ear from?

Answer 12

• Jugular wall/Bone
• Bulb of the internal jugular v

Question 13

• What makes up the lateral/membranous wall of the middle ear cavity?
• This separates the middle ear from what?

Answer 13

• Tympanic membrane
• External ear

Question 14

• What makes up the medial/labyrinthine wall of the middle ear cavity?
• This separates the middle ear from what?

Answer 14

• Promontory (from cochlea), oval window, round window. prominence of facial canal
• Inner ear

Question 15

• What makes up the posterior/mastoid wall of the middle ear cavity?
• This separates the middle ear from what?

Answer 15

• Aditus to mastoid antrum, canal for facial n
• Separates tympanic cavity from mastoid air cells and facial canal

Question 16

• What makes up the anterior/carotid wall of the middle ear cavity?
• Separates tympanic cavity from what?

Answer 16

• Opening of pharyngotympanic tube and canal for tensor tympani
• Internal carotid a.

Question 17

• What are the contents of the middle ear?

Answer 17

• Ossicles (malleus, incus, and stapes)
• Stapedius and tensor tympani muscles
• Chorda tympani n
• Tympanic plexes

Question 18

• Parts of the malleus

Answer 18

• Head
  
  • Epitympanic recess
  • Articulates with incus
• Neck
  
  • Lies against flaccid part of the tympanic membrane
  • Chorda tympani crosses medial surface
• Handle
  
  • Embedded in tympanic membrane
  • Tip at the umbo
  • Insertion of tensor tympani m.

Question 19

• Parts of the incus

Answer 19

• Head
  
  • In the epitympanic recess
  • Articulates with malleus
• Long limb
  
  • Articulates with stapes
• Short limb

Question 20

• Parts of the stapes

Answer 20

• Head
  
  • Articulates with incus
• Neck
  
  • Insertion for stapedius m
• Base
  
  • Inserts into oval window
• Two limbs

Question 21

• What are the two important muscles to consider when discussing the anatomy of the ear

Answer 21

• Tensor tympani m.
• Stapedius m.

Question 22

• Tensor tympani m.

Answer 22

• CN V (V3-Trigeminal N)
• Action: Prevents damage from loud sounds
• Pulls malleus medially, resulting in tensing of the tympanic membrane
• Inserts on handle of malleus

Question 23

• Stapedius m.

Answer 23

• Innervated by CN VII (Facial n.)
• Inserts onto neck of stapes
• Pulls stapes posteriorly and tilts its base in the oval window
• Prevents damage from loud sounds

Question 24

• What are the important nerves to consider when studying ear anatomy?

Answer 24

• Chorda tympani
• Tympanic n

Question 25

• Chorda tympani

Answer 25

• Branch of CN VII (Facial N)
• Carries parasympathetic fibers
• Taste to anterior 2/3 of tongue

Question 26

Tympanic N

Answer 26

• Branch of glossopharyngeal n (CN IX)
• Gives rise to the tympanic plexus-which gives rise to lesser petrosal n (parasympathetics)

Question 27

• Nerve summary

Answer 27

Question 28

• Describe parasympathetic (GVE) innervation to submandibular and sublingual glands

Answer 28

1. Chorda tymani branch arises from CNVII superior to stylomastoid foramen
2. Chorda tympani crosses tympanic cavity medial to handle of malleus
3. Chorda tympani passes through the petrotympanic fissure between tympanic and petrous part of temporal bone to join LINGUAL N (CN V3) in infratemporal fossa
4. Parasympathetic fibers of chorda tympani synapse in SUBMANDIBULAR galgnion (postsynaptic fibers follow arteries to glands)

Question 29

• Describe parasympathetic GVE innervation to the parotid gland

Answer 29

1. Tympanic nerve arises from CN IX (Glossopharyngeal n) and emerges with it from jugular foramen
2. Tympanic n enters middle ear via tympanic canaliculus in petrous part of the temporal bone
3. Tympanic n forms tympanic plexus on promontory of the middle ear
4. Lesser petrosal n arises as branch from tampanic plexus
5. Lesser petrosal n penetrates roof of tympanic cavity to enter middle cranial fossa
6. Lesser petrosal n leaves cranium through foramen ovale
7. Parasympathetic fibers synapse in otic ganglion
8. Postsynaptic fibers pass to parotid gland via branches of the auricolotemporal n.

Question 30

• Bony labyrinth

Answer 30

• Series of fluid filled cavities in petrous part of temporal bone
  
  • Cochlea
    
    • Large basal turn produces promontory of middle ear
  • Vestibule
  • Semicircular canals
• Filled with perilymph

Question 31

• Membranous labyrinth

Answer 31

• Series of communicating sacs and ducts that are suspended in the bony labyrinth
  
  • Vestibular labyrinth
    
    • Utricle
    • Saccule
  • Semicircular ducts
  • Cochlear labyrinth
    
    • Cochlear duct
• FILLED WITH ENDOLYMPH

Question 32

• Identify the components of the membranous labirynth
• What type of lymph is present?
• Which cranial nerve innervates these structures?

Answer 32

1. Scala vestibuli-perilymph (above vestibular membrane)
2. Cochlear duct (endolymph)
3. Scala tympani-perilymph (above vestibular membrane)

CN VIII (Vestibulocochlear n.)

Question 33

The spiral ganglion of the cochlea contain the cell bodies of _

Answer 33

• CN VIII (Vestibulocochlear n.)