Anatomy And Histology Of Ear

Question 1

External Ear blood supply

Answer 1

Posterior Auricular a and superficial temporal artery

Question 2

What part of ear does facial n innervate?

Answer 2

Pinna and inside rim of pinna

Question 3

Auriculotemporal n innervated what part of ear?

Answer 3

Front part, but not external acoustic meatus

Question 4

What innervates the external accoustic meatus?

Answer 4

Vagus and glossopharyngeal n

Question 5

What are the four parts of the tympanic membrane innervated by?

Answer 5

Superior: VII
Posterior: Great Auricular n
Inferior: Arnold n
Anterior: auriculotemporal

Question 6

Cough reflex of ear?

Answer 6

Afferent: Vagus
Efferent: Vagus and phrenic

Question 7

What is important about internal 1/3 of external accoustic meatus?

Answer 7

It’s the only place in body where skin overlaps bone

-site of bleeding

Question 8

From histo, how do you know if you’re in inner part of outer part of external acoustic meatus?

Answer 8

Outer ear: hair cells, sebaceous glands, sweat glands, connective tissue

Inner ear: basically skin over bone

Question 9

Walls of Middle Ear

Answer 9

Roof: Trigeminal Cavity

Floor: Jugular wall—jugular bulb behind from Sagittal sinus

Lateral: Membranous Wall-tympanic membrane

Medial: Labyrinthine Wall—semicircular canals and cochlea

Posterior: mastoid wall—mastoid process

Anterior: ICA

Question 10

Tympanic Membrane

Answer 10

Cone is oriented toward external acoustic meatus
-tip of malleus called umbo

Has a flaccid and tense part

Question 11

What is the function of the pharyngotympanic tube?`

Answer 11

Equalize pressure

Question 12

What muscles elevate the pharyngotympanic tube?

Answer 12

Levator Veli Palatini: CNX

Tensor Veli Palatini: CNV

Question 13

Pharyngotympanic Tube Histology

Answer 13

Pseudostratefied Epithelium (part of pharynx, remember?

Can see seromucus gland

Question 14

Tensor Tympani Muscle

Origin, Insertion, Innervation, Action

Answer 14

OI: surface of pharyngotympanic tube to handle of malleolus

Innervation: CNV

Action: Pulls on handle to tense membrane and reduce amplitude

Question 15

Stapedius M

Origin, Insertion, Innervation, Action

Answer 15

OI: pyramidial eminence to neck of stapes bone

Innervation: Facial CNVII

Action: reduce amplitude of stapes to reduce amount of sound transferred

Question 16

Bony labyrinth

Answer 16

Within petrous region of temporal bone; line with endosteum has membranous labyrinth within, separated by perilymph

Question 17

Membranous Labryrinth

Answer 17

Made of small sacs and tubes within bony labyrinth

Two different sections for different jobs

• Cochlear Duct: hearing
• Utricle, Saccule, Semicircular ducts: balance

Question 18

Hair cells

Answer 18

Kinocillium with stereocillia next to it

• if otocilia move in the direction towards kinocillium=depolarization
• if otocilia move in direction away from kinocillium=polarization

Question 19

Cochlea Mechanism

Answer 19

Oval window vibrates due to ossicles

Perilymph in scale vestibuli makes wave and crashes into vestibular membrane of scala media

Endolymph in scala media makes wave, crashes into basilar membrane of scala tympani
-endolymph also hits the tectorial membrane of organ of corti

Question 20

Organ of Corti

Answer 20

Hair cells embedded in tectoral membrane which extends from spiral lamina
-deflection of stereocilia depolarizers channels of hair cells

Question 21

Bipolar neuron cell bodies located in spiral ganglion are within what?

Answer 21

Modiolus=central axis

Question 22

Middle Ear function

Answer 22

Transmit vibrations and depressurization via pharyngotympanic tube

Question 23

Inner Ear: Balance Semicircular canals

Answer 23

Semicircular Canals w ampulla
-three canals w different axis filled with endolymph

Ampulla have cap called cupulla, which is what is displaced by fluid motion in canal
-rotational velocity

Question 24

Inner Ear Balance: Utricle and Saccule

Answer 24

Vestibule contains saccule and utricle
-each contains a macula w cluster of hair cells displaced by otoconia

For linear acceleration and gravity

Question 25

What is utricle for?

Answer 25

Linear acceleration and tilts head in horizontal plane

-U trip forward

Question 26

What is the saccule for?

Answer 26

Linear acceleration and head tilts in vertical plane

-u suck up

Question 27

Perilymph

Answer 27

Similar to CSF
-drains via perilymphic duct into subarachoid space
—why infections can spread from inner ear to brain

Question 28

Endolymph

Answer 28

Within membranous labyrinth and scala media
-scala vascularis makes it
—drains via endolymphatic duct into venous sinuses of dura mater

Question 29

How does cauliflower ear happen?

Answer 29

Ear is made of elastic cartilage

• when damaged, chondrogenesis of perichondrium happens
• causes thickening of ear

Question 30

Mastoiditis

Answer 30

Infection of mastoid cells
-can spread to cranial fossa via petrosqamous crania suture
—can spread into sigmoid sinus

Question 31

Tympanic Membrane damage

Answer 31

Medial ear pressure due to fluid

Most heal on own, but can be treated with antibiotics
—but not gentamicin!

Question 32

Otitis Media

Answer 32

Ear ache with possible fluid or pus in middle ear due to inflammation
-untreated can cause scarring of ossicles

Question 33

Why do little kids get otitis media more often?

Answer 33

Their pharyngotympanic tube is more horizontal, so fluid is more likely to build up there

Question 34

Menieres syndrome

Answer 34

Dizziness, vertigo, tinnitus, and hearing loss

-due to increase endolymph

Question 35

Viral labyrinthitis: symptoms and treatment

Answer 35

Dizziness, vertigo, tinnitus, and hearing loss

Treatment isn’t really anything; resolves within a week