Auditory A&p Exam 1 [Middle Ear]

Front 1

Tympanic Cavity

Three Levels

Back 1

1. Epitympanum
2. Mesotympanum
3. Hypotympanum

Front 2

Anterior Boundary of Tympanic Cavity

Back 2

Wall: Carotid

Anatomical Boundary: opening of pharyngotympanic tube (ET)

Neighboring Structure: carotid canal

Front 3

Lateral Boundary of Tympanic Cavity

Back 3

Wall: Membranous

Anatomical Boundary: TM

Neighboring Structure: external ear

Front 4

Superior Boundary of Tympanic Cavity

Back 4

Wall: Tegmental

Anatomical Boundary: Tegmen Tympani

Neighboring Structure: Middle cranial fossa

Front 5

Medial Boundary of the Tympanic Cavity

Back 5

Wall: Labyrinthine

Anatomical Boundary: Promontory overlying basal turn of cochlea

Neighboring Structures: inner ear, cerebrospinal fluid space

Front 6

Inferior Boundary of the Tympanic Cavity

Back 6

Wall: Jugular

Anatomical Boundary: temporal bone

Neighboring Structures: bulb of jugular vein, sigmoid sinus

Front 7

Posterior Boundary of the Tympanic Cavity

Back 7

Wall: Mastoid

Anatomical Boundary: aditus to mastoid atrium

Neighboring Structures: air cells of mastoid process, facial nerve canal

Front 8

Tympanic Cavity Walls

Back 8

1. Superior Wall - tegmen tympani
2. Inferior Wall - jugular wall
3. Lateral Wall - tympanic membrane
4. Medial Wall - labyrinthine (Promontory)
5. Posterior Wall - mastoid
6. Anterior Wall - ET

Front 9

Chorda Tympani Nerve

Back 9

• passes between incus and stapes
  
• VII Facial - sense of taste

Front 10

Back 10

1. Mastoid antrum
2. Aditus to mastoid antrum
3. Tegmen tympani
4. Epitympanic recess
5. Pharyngotympanic tube
6. Middle Ear
7. Mastoid process
8. Mastoid air cells

Front 11

Malleus

Back 11

1. Head
2. Anterior Process
3. Anterior Malleolar Ligament
4. Manubrium
5. Lateral Process
6. Neck

Front 12

Incus

Back 12

1. Articular Faucet (for malleus)
2. Short Process
3. Lenticular Process (articulates with stapes)
4. Long Process

Front 13

2 Ossicle Joints

Back 13

• Malleoincudal Joint (malleus to incus)
• Incudostapedial Joint (incus to stapes)

Front 14

Stapes

Back 14

1. Head (incostapedial joint/lenticular process)
2. Posterior crus
3. Footplate
4. Obturator foramen
5. Anterior crus

Front 15

Ossicle Ligaments

Back 15

1. Anterior Ligament of the Malleus
2. Lateral Ligament of the Malleus
3. Superior Ligament of the Malleus
4. Posterior Ligament of the Incus
5. Stapedius Muscle
6. Annular Ligament of the Stapes (binds the stapes to the OW)

Front 16

Tensor Tympani

Back 16

• inserts into upper manubrium malli
• contraction of TT tenses TM
• anterior most muscle
• completely encased in bony canal
• runs parallel to ET

Front 17

Stapedius Muscle

Back 17

• smaller than TT
• runs parallel to facial nerve canal
• contracts and draws footplate posteriorly at right angles to movement
• antagonistic (oppositional) to TT

Front 18

Function of the Middle Ear Transformer

Back 18

• converts mechanical energy into electrochemical energy
• middle ear enhances energy transmission (permits transmission of +99% energy)

Front 19

Amplifying Mechanisms of Middle Ear

Back 19

• Area Benefit (TM to OW)

• Lever Benefit

• TM Buckling (Buckling Effect)

Front 20

Amplifying Mechanism
Area Benefit

Back 20

• Area of TM 21x greater than OW
• Amplifies pressure up to 17 from TM to OW
• Force and pressure take place in amplification

24 - 25 dB gain as a result

Front 21

Amplifying Mechanism

Lever Benefit

Back 21

• movement of bones (ossicles)
• different length between malleus/incus creates a lever
• velocity is reduced, pressure increases

1.2 dB gain because of the difference in length between the manubrium and incus

Front 22

Amplifying Mechanism

TM Buckling

Back 22

• TM curves from rim of EAM at both ends to the point where manubrium attaches to TM
• Conical in shape
• As it moves in-and-out it buckles
• Malleus moves less than TM, increasing force and decreasing velocity

6 dB gain as a result

Front 23

Total Transformer Benefit from ME

Back 23

Area (25 dB) + Lever (1.3 dB) + Buckling (6 dB)
= 32 - 33 dB total!