Oral Mucosa 2 Flashcards
where is the body of the tongue derived from?
brachial arch 1
where is the root of the tongue derived from?
brachial arch 3
what is the characteristic of dorsal tongue?
epithelium mostly keratinized except key locations
lamina propria flexible
no submucosa
numerous papillae- rough surface
some papillae- taste buds
some papillae- innervated by somatosensory nerve endings
sensation not confined to tongue
how is taste innervavated?
taste buds- cn 7, 9, 10
how is touch innervated?
ab and adelta fibers
how is warmth innervated?
c fibers
how is cooling innervated?
a delta
how is pain innervated?
a delta and c fibers
what does the different fibers travel in?
cn10- anterior mouth
cn9- post tongue and pharynx
what are meissner’s corpuscles?
large axons (AB, larger alpha delta)
terminate in superficial lamina propria between rete pegs
complexes of nerve endings encapsulated by non-neuronal cells- schwann cells
dynamic forces (rapidly adapting)
what are merkel’s receptors?
large axons (AB, larger Alpha deltas)
fibers terminate at apices of rete pegs- epithelium
complexes of nerve endings and specialized epithelial (merkel cells)
merkel cells enfold nerve ending
static forces “slowly adapting”
how does meissner and merkel receptor cells differ?
both have very low threshold (highly sensitive)
but differ in response to the dynamic aspects of the stimulus
meissner sense initial deformation- if stay deformed- stop responding
merkel’s receptors maintain response even during a period of deformation but but during active touch
can merkel or meisssner mechanoreceptors code painful sensations?
no because their dynamic range does not extend to the noxious- because once reached threshold- they saturate out
what codes for painful sensations?
separate population of nociceptors with free nerve endings that end in lamina propria or epithelium
what are larger fibers (a beta and large a delta) responsible for?
touch
what are smaller fibers (small a delta and c) responsible for
thermal and pain
nociceptors
noxious mechanical forces- biting tongue, injection
harmful chemicals
painful thermal stimulation
what does all types of nerve fibers innervating oral mucosa have in common?
larger nerve bundles located in submucosa or deeper lamina propria- branch and terminate in more superficial lamina propria or epithelium
what is the function of the taste system?
detect chemicals in food
distinguish nutrients and non- nutritive substances
distinguish diff nutrients
detect harmful substances- poisons, caustic chemicals
what are the 5 classes of taste receptors to detect 5 classes of stimuli?
sugars (swee) amino acids (umami) salts esp sodium (salty) acids (sour) varied (alkaloid, purine base, glycosides)- bitter
taste bud
goblet-shaped cluster of 40-60 cells oriented at right angle to basal lamina from basal lamina to surface microvilli extend up to taste pore primary afferent fibers at base- some bud cells make synapse with these fibers
taste bud distribution
total around 8000
most 68% on tongue
but 27% on pharynx and larynx
5% on soft palate
fungifrm papillae
on dorsal anterior tongue (BA1)
innervated by chorda tympani branch of 7 (BA2)
around 1600 taste buds
most numerous at tip
strategically located to monitor food entering mouth
mushroom shaped
located among more numerous filiform papillae without taste buds
where is the keratin layer interruped?
at pore
between filiforms- give tongue flexibility
where are taste buds located on fungis?
dorsal surface
filiform papillae
spine shaped and heavily keratinized
do not contain buds
innervated only by somatosensory fibers
foliate papillae
2-9 parallel folds- dorsoventral orientation
around 1300 taste buds- densly packked
innervation- glossopharyngeal (ix, BA3)
lateral aspect of most posterior anterior tongue (posterior to molars, anterior to circumvallate)
strategic location to monitor food during chewing
where are foliate taste buds located?
in trenches
many buds/ foliate
closely assoviated with salivary glands- von ebner
circumvallate papilla
8-10
2400 buds- densely packed
central connective tissue core surrounded by trench
arranged in v on most posterior anterior tongue
strategic location- monitor food before swallowing
where are cv taste buds located?
in trench not dorsal surface
innervated by glossopharyngeal
many buds/cv
also closely associated with von ebner’s gland
are taste buds functionally redundant in ability to sense diff tastes?
yes
exception- taste buds on larynx- mainly respond to deviations from isotonicity- they signal to protect the airway
are there regional differences in taste sensitivity?
bitter more intense when in contact with post taste buds
but differences are relative not absolute
can a single fungiform paillae detect more than 1 quality?
yes
why is functional redundancy of taste system important?
makes it resilient in the face of partial taste loss
effects of damage to single taste nerves
perceptual effects of damage or anesthesia of a single taste nerve can be clearly detected with specific spatial testing
but when a person is allowed to use all of the taste buds in their mouth- effects of damage or anesthesia to a single nerve seem minor
reasons: functional redundancy and ability of cns to compensate for partial loss
what varies greatly between individuals?
number of taste papillae
declines with age slighly- loss of taste mostly olfactory involved
individual variation in taste sensitivity to specific substances
marked individual differences in ability to taste bitter ptc- inherited trait
specific for ptc and structurally related compounds
what are the bitter receptors?
tas2r
30 member fam
g-protein coupled
what is special about tas2r?
tas2r receptor for ptc- substitutions of 2/333 aa largely responsible for sensitivity differences
what vegetables taste signigicaltly more bitter in persons who are homozygous for ptc sensitve form of tas 2r?
mustard greens, turnips, broccoli- all have class of compds glycosinolates- same as ptc other veg- bitter melon, endive, raddicio- no difference in sensitivity for people with varying forms of tas2r receptor- veggies dont contain glucosinolates
genetic diff in receptors for sweet stimuli
differences in promoter region determine the number of copies of the sweet receptor that are transcribed- explains 16% of the individual variation in how intense sweet substances taste
people with most sweet receptor prefer least conc surgar
perigemmal cells
lateral aspect
around epitheloim but orientation diff
no synapses, microvilli
function unclear- support or renewal?
basal cells
base of bud
epithelial basal cells
renewal
elongate cells in center of bud cell types
dark (type1)
light(type 2 and 3)
type 1 dark
suggest suppporting role
no synapses
microvilli
function unclear
light cells
express receptors for taste substances and respond to taste stimili
type 3 light
sour
synapse with primary affeerent nerve
type 2 light
bitter, sweet amino acids
synapse with primary afferent nerve no
use atp to communicate with primary afferent taste nerves- atp released from type 2 cells without aid of typical synapse
are differential keratin expression observed in taste buds?
yes
what is k19?
occurs in type 1 2 and 3 cells of bud
contrast with surrounding keratinized epithelia
similar to basal layer of non-keratinized epithelia
k19 widely expresssed during development
k19 expression may reflect rapid turnover of taste receptor cells
time course of gustatory development
tongue- ew4 lingual papillae- ew8 taste buds 1st appear- ew8 taste pores appear- ew12 taste system develops early and is competent at birth
can natural taste preferences be altered by experience?
yes
formula experiment
