Histology of the olfactory and auditory senses Flashcards
nasal cavity - what are the regions?
cutaneous region
respiratory region - includes vomeronasal organ
olfactory region
rostral region of nasal cavity?
keratinised stratified squamous epithelium
mid vestibule of the nasal cavity?
thinner, non-keratinised stratified squamous epithelium
caudal region of nasal cavity?
transitional zone - varies from stratified cuboidal to non-ciliated pseudostratified columnar
respiratory region it part of and what does it contain?
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
respiratory epithelium?
ciliated pseudostratified columnar epithelium
vomeronasal organ?
VNO - located in ventral portion of nasal septum
bilateral blind-ended tubular organ?
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)
lateral region of VNO?
stratified cuboidal - rostral - incisive duct
ciliated pseudostratified columnar - caudal
medial region of VNO?
pseudostratified columnar epithelium has neurosensory, sustentacular and basal cells
olfactory region of nasal cavity?
dorsocaudal portion of the nasal cavity
thicker epithelium, more tubular glands and many nerve fibres compared to resp region
olfactory epithelium =
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)
olfactory glands?
located in the lamina propria/submucosa, contain pigmented cells
squamous cells line the duct to the epithlial surface
watery secretion to aid olfaction
primary site for chemically induced nasal tumours and why?
olfactory mucosa has very high levels of cytochrome P450 mono-oxygenase and this is the primary site for chemically induced nasal tumours
dorsal surface of tongue have papillae: which type?
filiform
circumvallate
fungiform
foliate
epithelium of the oral mucosa?
stratified squamous epithelium
taste buds located where?
taste buds located in circumvallate, fungiform and foliate papillae
contain specialised taste cells
structure of external ear?
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
auditory ossicles are?
malleus
incus
stapes
tympanic membrane does what?
it separates external and middle ear at base of external auditory meatus
external surface of tympanic membrane?
stratified squamous epithelium
internal surface of tympanic membrane?
simple squamous epithelium which is continuous with tympanic cavity
epithelial layers sandwich a layer of connective tissue of the tympanic membrane are made up of?
central circular arrangement of collagen fibres
peripheral radial arrangement of collagen fibres
less collagen in the dorsal (flaccid) part
tympanic cavity?
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
what does the auditory tube connect?
it connects the middle ear to nasopharynx
what is the auditory tube lined by?
lined by ciliated pseudostratified columnar epithelium (respiratory epithelium) with goblet cells
where does the auditory tube expand to?
expands ventrally to form the guttural pouch in horses
same histological features as auditory tube but lacks cartilage support
inner ear structure?
it is a bony labyrinth containing
3 semicircular canals
vestibule
cochlea: modiolus, osseous spiral maina, perilymph fluid
stria vascularis of the inner ear is made up of what cells?
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
what does stria vascularis produce?
it produces endolymph
where is the stria vascularis found?
in the inner ear - part of the membranous labyrinth
organ of corti?
it sits on dorsal surface of basilar membrane
contains the acoustically sensitive hair cells that have stereocilia
support cells
stereocilia?
cilia longer toward outer edge
tectorial membrane of organ of corti?
extends from spiral limbus (elevation of connective tissue from osseous spiral lamina)
proteinaceous
in contact with stereocilia of hair cells
what causes the stereocilia to be displaced?
vibration in the tectorial membrane displaces the stereocilia leading to signal
what is the membranous labyrinth?
it is the simple squamous epithelium lining the bony labyrinth
where is the utricle in the vestibule of the inner ear?
caudodorsal
where is the saccule in the vestibule of the inner ear?
rostroventral
what are the two parts of utriculo-saccular duct of the vestibule of the inner?
endolymphatic duct and endolymphatic sac
what fluid is found in the inner ear?
endolymph fluid
