Oral Mucosa 2

Question 1

where is the body of the tongue derived from?

Answer 1

brachial arch 1

Question 2

where is the root of the tongue derived from?

Answer 2

brachial arch 3

Question 3

what is the characteristic of dorsal tongue?

Answer 3

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

Question 4

how is taste innervavated?

Answer 4

taste buds- cn 7, 9, 10

Question 5

how is touch innervated?

Answer 5

ab and adelta fibers

Question 6

how is warmth innervated?

Answer 6

c fibers

Question 7

how is cooling innervated?

Answer 7

a delta

Question 8

how is pain innervated?

Answer 8

a delta and c fibers

Question 9

what does the different fibers travel in?

Answer 9

cn10- anterior mouth

cn9- post tongue and pharynx

Question 10

what are meissner’s corpuscles?

Answer 10

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)

Question 11

what are merkel’s receptors?

Answer 11

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”

Question 12

how does meissner and merkel receptor cells differ?

Answer 12

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

Question 13

can merkel or meisssner mechanoreceptors code painful sensations?

Answer 13

no because their dynamic range does not extend to the noxious- because once reached threshold- they saturate out

Question 14

what codes for painful sensations?

Answer 14

separate population of nociceptors with free nerve endings that end in lamina propria or epithelium

Question 15

what are larger fibers (a beta and large a delta) responsible for?

Answer 15

touch

Question 16

what are smaller fibers (small a delta and c) responsible for

Answer 16

thermal and pain

Question 17

nociceptors

Answer 17

noxious mechanical forces- biting tongue, injection
harmful chemicals
painful thermal stimulation

Question 18

what does all types of nerve fibers innervating oral mucosa have in common?

Answer 18

larger nerve bundles located in submucosa or deeper lamina propria- branch and terminate in more superficial lamina propria or epithelium

Question 19

what is the function of the taste system?

Answer 19

detect chemicals in food
distinguish nutrients and non- nutritive substances
distinguish diff nutrients
detect harmful substances- poisons, caustic chemicals

Question 20

what are the 5 classes of taste receptors to detect 5 classes of stimuli?

Answer 20

sugars (swee)
amino acids (umami)
salts esp sodium (salty) 
acids (sour)
varied (alkaloid, purine base, glycosides)- bitter

Question 21

taste bud

Answer 21

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

Question 22

taste bud distribution

Answer 22

total around 8000
most 68% on tongue
but 27% on pharynx and larynx
5% on soft palate

Question 23

fungifrm papillae

Answer 23

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

Question 24

where is the keratin layer interruped?

Answer 24

at pore

between filiforms- give tongue flexibility

Question 25

where are taste buds located on fungis?

Answer 25

dorsal surface

Question 26

filiform papillae

Answer 26

spine shaped and heavily keratinized do not contain buds innervated only by somatosensory fibers

Question 27

foliate papillae

Answer 27

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

Question 28

where are foliate taste buds located?

Answer 28

in trenches many buds/ foliate closely assoviated with salivary glands- von ebner

Question 29

circumvallate papilla

Answer 29

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

Question 30

where are cv taste buds located?

Answer 30

in trench not dorsal surface innervated by glossopharyngeal many buds/cv also closely associated with von ebner's gland

Question 31

are taste buds functionally redundant in ability to sense diff tastes?

Answer 31

yes | exception- taste buds on larynx- mainly respond to deviations from isotonicity- they signal to protect the airway

Question 32

are there regional differences in taste sensitivity?

Answer 32

bitter more intense when in contact with post taste buds | but differences are relative not absolute

Question 33

can a single fungiform paillae detect more than 1 quality?

Answer 33

yes

Question 34

why is functional redundancy of taste system important?

Answer 34

makes it resilient in the face of partial taste loss

Question 35

effects of damage to single taste nerves

Answer 35

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

Question 36

what varies greatly between individuals?

Answer 36

number of taste papillae | declines with age slighly- loss of taste mostly olfactory involved

Question 37

individual variation in taste sensitivity to specific substances

Answer 37

marked individual differences in ability to taste bitter ptc- inherited trait specific for ptc and structurally related compounds

Question 38

what are the bitter receptors?

Answer 38

tas2r 30 member fam g-protein coupled

Question 39

what is special about tas2r?

Answer 39

tas2r receptor for ptc- substitutions of 2/333 aa largely responsible for sensitivity differences

Question 40

what vegetables taste signigicaltly more bitter in persons who are homozygous for ptc sensitve form of tas 2r?

Answer 40

``` 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 ```

Question 41

genetic diff in receptors for sweet stimuli

Answer 41

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

Question 42

perigemmal cells

Answer 42

lateral aspect around epitheloim but orientation diff no synapses, microvilli function unclear- support or renewal?

Question 43

basal cells

Answer 43

base of bud epithelial basal cells renewal

Question 44

elongate cells in center of bud cell types

Answer 44

dark (type1) | light(type 2 and 3)

Question 45

type 1 dark

Answer 45

suggest suppporting role no synapses microvilli function unclear

Question 46

light cells

Answer 46

express receptors for taste substances and respond to taste stimili

Question 47

type 3 light

Answer 47

sour | synapse with primary affeerent nerve

Question 48

type 2 light

Answer 48

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

Question 49

are differential keratin expression observed in taste buds?

Answer 49

yes

Question 50

what is k19?

Answer 50

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

Question 51

time course of gustatory development

Answer 51

``` tongue- ew4 lingual papillae- ew8 taste buds 1st appear- ew8 taste pores appear- ew12 taste system develops early and is competent at birth ```

Question 52

can natural taste preferences be altered by experience?

Answer 52

yes | formula experiment