The Ear

Question 1

Transmission of Sound

Answer 1

• Sound enters external acoustic meatus
• Vibrates tympanic membrane
• moves Malleus, then Incus, then Stapes
• vibrates oval window
• transmits waves in scala vestibuli and scala tympani
• vibrates membrane of cochlear duct
• spinal nerve VIII (Vestibulocochlear nerve)

Question 2

Contents of external ear

Answer 2

• Auricle - collects sound
• External Acoustic Meatus

Question 3

Contents of Middle Ear

Answer 3

• Auditory ossicles
• Stapedius
• Chorda Tympani
• Tensor tympani
• Tympanic nerve plexus

Question 4

Contents of Inner Ear

Answer 4

• Vestibulocochlear organ - hearing and balance

Question 5

What do all chromosomal abnormalities have in common

Answer 5

Ear developmental anomalies

Question 6

Muscles, Nerves (+ spinal levels), and Vascularization of Auricle

Answer 6

• Auricular musles (facial expression muscles)
• Blood supply via terminal branch of External Carotid Artery
• Innervation - Genereal Sensory fibers of
  
  • Greater auricular nerve (C2)
  • Lesser occipital nerve (C2-C3)
  • Auricotemporal nerve (V3)
  • VII (Facial)
  • IX (Glossopharyngeal)
  • X (Vagus)

Question 7

Innervation of External Acoustic Meatus

Answer 7

• Auricotemporal Nerve (Branch of Mandibular V3)
• VII
• IX
• X

Question 8

Future ear bones (embryology)

Answer 8

Mesnchymal condensation

Question 9

Germ layers of middle ear

Answer 9

• Ectoderm - Tympanic membrane
• Mesoderm - Eardrum
• Ectoderm - External Ear

Question 10

How does the middle ear communicate with the mastoid area?

Answer 10

Pharyngotympanic tube

Question 11

Innervation of Middle Ear Structures

Answer 11

Tympanic Plexus

• Branch of IX (Glossopharyngeal nerve) - Visceral Sensory fibers

Question 12

Bone separating middle ear cavity from mid cranial fossa

Answer 12

Tegmen tympani

Question 13

Vessel running directly under floor of middle ear

Answer 13

Internal Jugular Vein

Question 14

Function of Pharyngotympanic tube; what is it opened by?

Answer 14

• Equilize pressureon both sides of tympanic membrane
• opened by tensor veli palatini and levator veli palatini

Question 15

Tensor Tympani

Answer 15

• Innervation : V3 branchiomotor
• Function: Pulls tympanic membrane to reduce vibrations after loud noises

Question 16

Stapedius

Answer 16

• Innervation: VII - branchiomotor
• Function: Pulls stapes posteriorly to prevent excessive oscillation after loud noise

Question 17

Tympanic Plexus

Answer 17

• Made from Branch of IX Branchiomotor (Visc sensory & Visc. parasympathetic) and Internal Carotid Plexus (sympathetic)
• gives rise to Lesser Petrosal Nerve
  
  • exits jugular foramen
  • enters otic ganglion
  • parasympathetic innervation to Parotid Gland

Question 18

Facial artery travels with what through what opening in cranium

Answer 18

• Travels with Vestibulocochlear nerve (VIII) through Internal acoustic meatus
  *

Question 19

Ganglionic body for facial nerve in Temporal Bone

Answer 19

Geniculate ganglion

• Cell bodies for
  
  • General sensory fibers (Ear)
  • special sensory fibers (taste)
  • Visceral sensory fibers (palate)

Question 20

Branches of Facial nerve in Temporal Bone

Answer 20

1. Greater petrosal nerve
2. Nerve to stapedius
3. Chorda tympani

Question 21

Contents of Bony Labyrinth

Answer 21

• Vestibule
• 3 Semicircular canals
• Cochlea

Contains perilymph, similar to CSF

Question 22

Membranous Labyrinth

Answer 22

• Cochlear duct - Hearing
• 3 semicircular ducts - balance
• Utricle - balance
• Saccule - balance

Question 23

Vestibule (part of bony labyrinth)

Answer 23

• Recieves vibrations from oval window
• Communicates with Cochlea and Semicircular canals
• vestibular aqueduct passes to cranial cavity
  
  • stores excess endolymph made in membranous labyrinth)

Question 24

Semicircular Canals (part of bony labyrinth)

Answer 24

Connected to Vestibule

Covers Semicrircular Ducts

Question 25

Semicircular Canals

Answer 25

• Part of membranous labyrinth
• important in **BALANCE **
• drain into utricle
• convey information about rotational motion

Question 26

Utricle

Answer 26

• BALANCE
• responds to **linear accerleation **
• gets endolymph from **semicircular ducts **

Question 27

Endolymphatic Duct

Answer 27

• Drains from utricle/saccule into vestibular aqueduct
• Ultimately to endolymphatic sac

Question 28

Cochlea (internal ear)

Answer 28

• part of bony labyrinth
• twists self around bony core - Modiolus
• Cochlear duct separates scala tympani and scala vestibuli
  
  • continuous w/ eachother at helicotrema
• Cochlear aqueduct connects perilymph to subarachnoid space

Question 29

Contents of cochlear duct vs contents of scala vestibuli/scala tympani

Answer 29

• Cochlear duct - filled with endolymph
• Scala tympani/scala vestibuli - filled with **perilymph **

Question 30

Organ of hearing

Answer 30

• Spiral organ of corti
• inside Cochelar duct

Question 31

Vestibulocochlear Nerve (VIII)

Answer 31

• Origin: Pons
• Course: through internal acoustic meatus (IAM)
• Components: special sensory
• Ganglion: cochlear (spiral) and vestibular ganglia (sensory cell bodies here)
• Distribution: Cochlea, semicircular canals, utricle, saccule
• Function: Hearing & equilibium

Question 32

Equilibrium responder directions

Answer 32

• Utricle - Horizontal (linear) acceleration
• Saccule - Vertical (linear ) acceleration
• (3) Semicircular canals - angular acceleratoin

Question 33

Diagram of ear endolymph/perilymph and structures

Answer 33