2 - Hatcher - Ear Histology

Question 1

External Ear

Answer 1

Auricle, Pinna = Funnel to collect sound waves

External Auditory Meatus (auditory canal): S-shaped tube that leads to tympanic membrane

Lined with stratified squamous epithelium

Question 2

Where does the auditory canal end?

Answer 2

Tympanic Membrane (eardrum)

Question 3

Middle Ear

Answer 3

Contains tympanic cavity

Contains Ossicles: Malleus, Incus, Stapes

Communicates with auditory tube (Eustacian tube)

Question 4

Tympanic Cavity

Answer 4

Air filled space in temporal bone

Question 5

Where does the stapes vibrate?

Answer 5

Over the oval window to transfer vibrations to the inner ear

Question 6

Auditory Tube

Answer 6

Connects middle ear cavity to pharynx (throat)

Below temporal bone the tube is typically collapsed–opening it during swallowing equalizes pressure in middle ear

Infection can travel form throat to middle ear through auditory tube

Question 7

Ear Infection

Answer 7

Most common in children, 1/3 of all peds visits

Chronic infections can be treated by myringotomy “ear tubes”

Question 8

Semicircular Canals vs Cochlea

Answer 8

Semicircular Canals = Balance/Acceleration

Cochlea = Hearing

Question 9

Location of Semicircular Canals / Cochlea?

Answer 9

Located in petrous portion of temporal bone

Question 10

Osseus

Answer 10

Bony canal in temporal bone

Question 11

Auditory System of Inner Ear

Answer 11

Cochlear Duct (Organ of Corti)

Question 12

Vestibular System of Inner Ear

Answer 12

Vestibule:

Ultricle (Macula)

Saccle (Macula)

Semicircular Ducts (crista ampullaris):

Horizontal (location of sens organ)

Question 13

Perilymph

Endolymph

Answer 13

Fluid between the osseous and membranous labryinth

Fluid within the membranous labyrinth

Question 14

Scala Vestibuli

Answer 14

Filled with perilymph

Anterior to Cochlear duct and Scale Tympani

Question 15

Cohlear Duct

Answer 15

Filled with endolymph

In between Scala Vestibuli and Scale Tympani

Question 16

Scale Tympani

Answer 16

Filled with perilymph

Posterior to Scala Vestibuli and Cohlear Duct

Question 17

Organ of Corti

Answer 17

Consists of hair cells supported on basilar membrane

Stereocilia on hair cells project into overlying gel-like TECTORIAL membrane

Question 18

Steps to Firing of Organ of Corti

Answer 18

1. Pressure waves (generated by stapes at oval window) vibrate the perilymph in scala vestibuli
2. Movement vibrates vestibular membrane and endolymph within cochlear duct
3. Movement vibrates basilar membrane and distorts stereocilia of hair cells w/in tectorial membrane
4. Displacement of hair cells initiates nerve signal in cochlear division of Cranial Nerve 8

Question 19

What separates Scala Vestibuli and Cochlear Duct?

Answer 19

Vestibular Membrane

Question 20

How is perception of sound terminated?

Answer 20

Fluid wave is dissipated at round window

Question 21

Sense / Sense Organ

Hearing?

Static Equilibrium?

Dynamic Equilibrium?

Answer 21

Hearing - Organ of Corti (in Cochlear Duct)

Static Equilibrium - Macula (in Utricle/Saccule)

Dynamic Equilibrium - Crista Ampullaris (in Semicircular Ducts)

Question 22

What detects static position and linear acceleration of the head?

Answer 22

Utricle / Saccule

Question 23

What detects rotational movement of head relative to body?

Answer 23

Semicircular Canals

Located in expanded proximal region (ampulla) of each semicircular canal