Histology of the olfactory and auditory senses

Question 1

nasal cavity - what are the regions?

Answer 1

cutaneous region
respiratory region - includes vomeronasal organ
olfactory region

Question 2

rostral region of nasal cavity?

Answer 2

keratinised stratified squamous epithelium

Question 3

mid vestibule of the nasal cavity?

Answer 3

thinner, non-keratinised stratified squamous epithelium

Question 4

caudal region of nasal cavity?

Answer 4

transitional zone - varies from stratified cuboidal to non-ciliated pseudostratified columnar

Question 5

respiratory region it part of and what does it contain?

Answer 5

it is the caudal 2/3 of the nasal cavity
it contains several cell types e.g. ciliated cells, secretory cells, brush cells, basal cells

Question 6

respiratory epithelium?

Answer 6

ciliated pseudostratified columnar epithelium

Question 7

vomeronasal organ?

Answer 7

VNO - located in ventral portion of nasal septum

Question 8

bilateral blind-ended tubular organ?

Answer 8

internal epithelial duct (vomeronasal duct), middle propria submucosa and an external cartilaginous support
Rostrally - incisive duct - connects the nasal cavity with the oral cavity (except horses - blind ended ventrally)

Question 9

lateral region of VNO?

Answer 9

stratified cuboidal - rostral - incisive duct
ciliated pseudostratified columnar - caudal

Question 10

medial region of VNO?

Answer 10

pseudostratified columnar epithelium has neurosensory, sustentacular and basal cells

Question 11

olfactory region of nasal cavity?

Answer 11

dorsocaudal portion of the nasal cavity
thicker epithelium, more tubular glands and many nerve fibres compared to resp region

Question 12

olfactory epithelium =

Answer 12

ciliated pseudostratified columnar cells with:
neurosensory olfactory cells (bipolar neurons) - connect to olfactory bulb via olfactory nerve (CN I ) passing through cribiform plate of ethmoid bone
support cells/sustentacular cells (columnar cells with narrow base and wide apical portion)

Question 13

olfactory glands?

Answer 13

located in the lamina propria/submucosa, contain pigmented cells
squamous cells line the duct to the epithlial surface
watery secretion to aid olfaction

Question 14

primary site for chemically induced nasal tumours and why?

Answer 14

olfactory mucosa has very high levels of cytochrome P450 mono-oxygenase and this is the primary site for chemically induced nasal tumours

Question 15

dorsal surface of tongue have papillae: which type?

Answer 15

filiform
circumvallate
fungiform
foliate

Question 16

epithelium of the oral mucosa?

Answer 16

stratified squamous epithelium

Question 17

taste buds located where?

Answer 17

taste buds located in circumvallate, fungiform and foliate papillae
contain specialised taste cells

Question 18

structure of external ear?

Answer 18

vertical canal
horizontal canal
cartilage supporting the tube
lined by skin similar to the rest of the body
hair follicles sebaceous glands and apocrine glands/ceruminous glands

Question 19

auditory ossicles are?

Answer 19

malleus
incus
stapes

Question 20

tympanic membrane does what?

Answer 20

it separates external and middle ear at base of external auditory meatus

Question 21

external surface of tympanic membrane?

Answer 21

stratified squamous epithelium

Question 22

internal surface of tympanic membrane?

Answer 22

simple squamous epithelium which is continuous with tympanic cavity

Question 23

epithelial layers sandwich a layer of connective tissue of the tympanic membrane are made up of?

Answer 23

central circular arrangement of collagen fibres
peripheral radial arrangement of collagen fibres
less collagen in the dorsal (flaccid) part

Question 24

tympanic cavity?

Answer 24

when healthy - filled with air contains auditory ossicles and muscles lined by simple squamous epithelium thin layer of connective tissue occasional ciliated cells continuous with auditory tube (Eustachian tube) which connects to nasopharynx

Question 25

what does the auditory tube connect?

Answer 25

it connects the middle ear to nasopharynx

Question 26

what is the auditory tube lined by?

Answer 26

lined by ciliated pseudostratified columnar epithelium (respiratory epithelium) with goblet cells

Question 27

where does the auditory tube expand to?

Answer 27

expands ventrally to form the guttural pouch in horses same histological features as auditory tube but lacks cartilage support

Question 28

inner ear structure?

Answer 28

it is a bony labyrinth containing 3 semicircular canals vestibule cochlea: modiolus, osseous spiral maina, perilymph fluid

Question 29

stria vascularis of the inner ear is made up of what cells?

Answer 29

stratified cuboidal epithelium: basal cells - flat cells acting as barrier between marginal cells and spiral ligament intermediate cells - contains melanin - generate electrical potential (high K+, +80mV) marginal cells - pump out Na+ from endolymph

Question 30

what does stria vascularis produce?

Answer 30

it produces endolymph

Question 31

where is the stria vascularis found?

Answer 31

in the inner ear - part of the membranous labyrinth

Question 32

organ of corti?

Answer 32

it sits on dorsal surface of basilar membrane contains the acoustically sensitive hair cells that have stereocilia support cells

Question 33

stereocilia?

Answer 33

cilia longer toward outer edge

Question 34

tectorial membrane of organ of corti?

Answer 34

extends from spiral limbus (elevation of connective tissue from osseous spiral lamina) proteinaceous in contact with stereocilia of hair cells

Question 35

what causes the stereocilia to be displaced?

Answer 35

vibration in the tectorial membrane displaces the stereocilia leading to signal

Question 36

what is the membranous labyrinth?

Answer 36

it is the simple squamous epithelium lining the bony labyrinth

Question 38

where is the utricle in the vestibule of the inner ear?

Answer 38

caudodorsal

Question 39

where is the saccule in the vestibule of the inner ear?

Answer 39

rostroventral

Question 40

what are the two parts of utriculo-saccular duct of the vestibule of the inner?

Answer 40

endolymphatic duct and endolymphatic sac

Question 41

what fluid is found in the inner ear?

Answer 41

endolymph fluid