Anatomy of the Ear

Question 1

Parts of the temporal bone

Answer 1

Squamosa
Mastoid
Petrous
Tympanic

Question 2

Muscles attached to mastoid process

Answer 2

SCM
Splenius capitus
Longus capitus
Digastric
Ant, sup, and post auricular

Question 3

What type of cartilage is the ear made of?

Answer 3

Auricle - elastic

Cartilaginous canal - fibrocartilage

Question 4

EAC composition

Answer 4

1/3: cartilage, sebaceous glands, ceruminous glands, hair

2/3: bone

Question 5

EAC boundaries

Answer 5

Ant: Mandibular fossa, parotid
Post: mastoid
Sup: Epitympanic recess (medial), cranial cavity (lateral)
Inf: parotid

Question 6

What bone makes bony canal of EAC

Answer 6

Tympanic portion of T bone: ant, floor, & part of post

Squamous: rest of post, roof

Question 7

Epitympanum boundaries

Answer 7

Med: LSCC, CN7
Sup: Tegmen
Ant: zygomatic arch
Lat: Squamous tbone (scutum)
Inf: fossa incudis
Post: aditus

Question 8

Tympanic cavity boundaries

Answer 8

Roof: tegmen
Floor: jugular wall & styloid prominence
Post: mastoid, stapedius, pyramidal prominence
Ant: carotid wall, eustachian tube tensor tympani
Med: labyrinthine wall
Lat: TM, scutum (laterosuperior)

Question 9

How is the auricle attached to the head?

Answer 9

1. Skin
2. An extension of cartilage to EAC cartilage
3. Ligaments
   - Ant lig: zygoma to helix & tragus
   - Sup lig: EAC to spine of helix
   - Post lig: mastoid to concha
4. Muscles: ant, sup, and post auricular muscles

Question 10

Notch of Rivinus

Answer 10

The notch on the squamosa, medial to which lies Shrapnell’s membrane.
The tympanic ring is not a complete ring, w/ the dehiscence superiorly

Question 11

Shrapnell’s membrane

Answer 11

Par’s flaccida

Question 12

Meckel’s cave

Answer 12

The concavity on the sup portion of the temporal bone in which the gasserian ganglion (V) is located

Question 13

Dorello’s canal

Answer 13

B/w the petrous tip and the sphenoid bone

The groove for CN VI

Question 14

Gradenigo synd

Answer 14

2/2 to petrositis w/ involvement of CN VI

• Pain behind the eye
• Diplopia
• Aural discharge

Question 15

Macewen’s triangle

Answer 15

Suprameatal triangle
Posterior and superior to EAC
Bound at the meatus by the spine of Henle (otherwise called the suprameatal spine)
This approximates the position of the antrum medially.
Tegmen mastoideum is the thin plate over the antrum

Question 16

Trautmann’s triangle

Answer 16

Demarcated by the bony labyrinth, the sigmoid sinus, and the superior petrosal sinus or dura

Question 17

Citelli’s angle

Answer 17

The sinodural angle
Located b/w the sigmoid sinus and the middle fossa dura plate
Others consider the superior side of Trautmann’s triangle to be Citelli’s angle

Question 18

Solid angle

Answer 18

angle formed by the 3 SCCs

Question 19

Scutum

Answer 19

Thin plate of squamousa bone that constitutes the lateral wall of the epitympanum

Question 20

Mandibular fossa boundaries

Answer 20

zygomatic, squamosa, & tympanic bones

Question 21

Huguier’s canal

Answer 21

Transmits the chorda tympani out of the t bone anteriorly

Is lateral to the roof of the protympanum

Question 22

Huschke’s foramen

Answer 22

Located on the anterior tympanic plate along a nonossified portion of the plate
Near the fissures of Santorini

Question 23

Porus acusticus

Answer 23

The “mouth” of the IAC

The canal is divided horizontally by the crista falciformis

Question 24

3 parts of the inner ear

Answer 24

1. Pars superior: vestibular labyrinth (utricle and SCCs)
2. Pars inferior: cochlea and saccule
3. Endolymphatic sac and duct

Question 25

4 small outpocketings from the perilymph space

Answer 25

1. Along the endolymphatic duct 2. Fissula ante fenestram 3. Fossula post fenestram 4. Periotic duct

Question 26

4 openings into the t bone

Answer 26

1. IAC 2. Vestibular aqueduct 3. Cochlear aqueduct 4. Subarcuate fossa

Question 27

Ponticulum

Answer 27

Ridge of bone b/w the oval window niche and the sinus tympani

Question 28

Subiculum

Answer 28

Ridge of bone b/w the round window niche and the sinus tympani

Question 29

Korner's septum

Answer 29

Separates the squamosa from the petrous air cells

Question 30

Scala communis

Answer 30

Where the scala tympani joins the scala vestibuli | The helicotrema is at the apex of the cochlea where the two join

Question 31

Petrous pyramid

Answer 31

Strongest bone in the body

Question 32

IAC diameter

Answer 32

8 mm is the upper limit

Question 33

Cochlear aqueduct

Answer 33

Bony channel connecting scala tympani of the basal turn with the subarachnoid space of the posterior cranial cavity Avg length in adults in 6.2 mm

Question 34

Tympanic plexus

Answer 34

= V3, IX, and X V3 --> auriculotemporal n IX --> Jacobson's n X --> Auricular n

Question 35

Outer ear blood supply

Answer 35

Posterior auricular art Superficial temporal art (Both from ECA)

Question 36

Foramen of Huschke

Answer 36

The incomplete ossification of the anterior bony canal produces an opening into the infratemporal region called this. Means of extension of malignancy to deep lobe of parotid.

Question 37

Fissures of Santorini

Answer 37

Naturally occurring defects in the cartilaginous portion of EAC. Provide avenue of spread to superficial parotid

Question 38

Pyramidal eminence

Answer 38

Pyramidal projection of bone in the posterior mesotympanum from which the stapedial muscle originates

Question 39

Cochleariform process

Answer 39

Bone in the anterior mesotympanum that anchors the tensor tympani muscle which turns 90 deg and becomes a tendon that connects to the malleus

Question 40

Ponticulus

Answer 40

Ridge of bone between round and oval windows

Question 41

Subiculum

Answer 41

Ridge of bone just anterior to round window

Question 42

Embryologic origin of ossicles

Answer 42

Attic portion are from 1st branchial arch Mesotympanum portion are from 2nd branchial arch Stapes footplate is from the otic capsule (primordial otocyst)

Question 43

Where does the chorda tympani exit the middle ear?

Answer 43

Petrotympanic fissure

Question 44

What are the branches off the facial nerve within the temporal bone?

Answer 44

1. GSPN 2. Stapedial 3. Chorda tympani

Question 45

Function of chorda tympani

Answer 45

1. Taste to ant 2/3 tongue | 2. PARA to submandibular and sublingual glands

Question 46

Function of GSPN

Answer 46

PARA to lacrimal and minor salivary glands of nose

Question 47

Facial recess

Answer 47

Space medial to the end of the posterior ear canal but lateral to the vertical segment of CN VII

Question 48

Sinus tympani

Answer 48

The space medial o the vertical segment of CN VII. This is posterior to the posterior crus of the stapes

Question 49

Ampullopetal endolymph flow

Answer 49

Displacement of the cupula towards the vestibule provides an excitatory response. Occurs in the HSCC. The kinocilium are this oriented towards the utricle side

Question 50

Ampullofugal endolymph flow

Answer 50

Displacement of the cupula towards the canal provides an excitatory response. Occurs in SSCC and PSCC. Thus, the kinocilia are oriented towards the canal side.

Question 51

Stria vascularis

Answer 51

Forms the outer wall of the scala media and sits within the spiral ligament. Highly vascular and metabolically active because its job is to create the high potassium concentration of the scala media. Acts as the battery whose electrical current powers hearing.

Question 52

Outer hair cell function in the cochlea

Answer 52

Amplifier Uses electromotility to elongate and shorten in response to receptor potential generated by stereocilia This generates sound (OAE) This refines the sensitivity and frequency selectivity of the mechanical vibrations of the cochlea.