Oral Mucosa Flashcards
what is the mouth lined by?
moist mucous membrane
what is mucous membrane?
organ composed of two tissues- epithelium and lamina propria
where does the blood vessels penetrate?
lamina propria/submucosa- do not penetrate in epithelium
arise in connective tissue
where are salivary glands?
lamina propria or submucosa (main location)- lubricate surface via ducts
how does oral mucosa serve as protection?
barrier between outside world and deeper tissue of oral cavity- epithelium>basal lamina
epithelium composed of sheets of cells connected via desmosome- keep things out of underlying tissue
also antimicrobial functions with immune cells more in lamina propria than epithelium. epithelial cells called beta defensins is secreted.
how does the oral mucosa help ingestion?
flexibility, moist surface- help us eat or otherwise can’t chew swallow, pass food anterior to posterior
is oral mucosa highly innervated?
yes
how does oral mucosa contrast with pulp and pdl
capable of more types of sensation
what fibers are in dentin and pulp?
c, adelta, abeta fibers- mostly pain
what fibers are in pdl?
c and a delta fibers- pain
a beta- proprioceptive
what fibers are in oral mucosa?
abeta- touch
adelta and c- pain
adelta and c- thermal
adelta- possible pain
what are the two types of tissue that are always present in oral mucosa?
epithelium and connective tissue- lamina propria and sometimes submucosa
what cells are all oral epithelium made of?
stratified squamous epithelium
*skin- stratified squamous
lining of blood vessels- endothelium- simple squamous epithelium
lining of stomach- simple columnar
is epithelium self renewing?
yes
deep layers= cell division
superficial layers- migrate and mature, surface- sloughed off
what happens with fast turnover?
can speed healing but also can make tissue more vulnerable to conditions that affect cell division (chemotherapy and radiotherapy)
turnover times for various epithelia
fastest- gut, junctional epithelium, taste buds, cheek, gingiva, skin
what occupies the most volume in epithelium?
cells
what cells are most numerous in epithelium
keratinocytes
what are the non-keratinocytes and where are they located?
melanocytes- pigment cells- make melanin- basal layers
langerhans (dendritic) cells- immune- supra-basal layers
merkel cells- sensory- basal layers
all clear cells
what are clear cells?
revealed by lack of cytokeratin staining
what do langerhan cells look like
simialr to melanocyte- but in suprabasal layers
what are melanocyte
have processes where melanin can be transported out. transferred to keratinocytes- darker skin
what are different oral regions lined by?
keratinized epithelium ex. gingva, hard palate
or non- keratinized epithelium ex. alveolar mucosa, buccal mucosa, soft palate
keratinized vs nonkeratinized
both: basal layer- cell division
both: prickle layer- appearance due to desmosomes- stratum spinosum
more superficial layers- distinct
granular layer in keratinized and intermediate layer in non-keratinized
keratinized layer in keratinized- no organelles, dehydrated, tougher
superficial layer in non- keratinized- organelles, flexible
what does all epithelial cells have?
keratinocytes- they contain cytokeratins
what are cytokeratins
large (30) multigene family of proteins
assemble into intermediate filaments, provide cytoskeletal support
2 major groups: type 1: acidic, type 2: basic
how are cytokeratins assembled?
central helical core flanked by non-helical ends
each cell expresses at least 2 cytokeratins- one of each type
assemble into coiled heterodimer
~10k heterodimers- intermediate filament (10nM)
coiled dimer assemble again and again until get robust fibers- intermediate filament
characteristics of cytokeratins
mechanically tough- provide support- intermediate filaments- strongest cytoskeletal element- resist mechanical force without breaking
intracellular component of demosomes (cell-cell junction) and hemidesmosomes (junctions between basal cells and basal lamina)
what derives epidermolysis bullosa simplex (EB simplex)
mutations in cytokeratins (basal layer)
rare
blistering in response to minor trauuma
most severe in epidermis but also oral consequences
where do characteristic cytokeratins reside?
different epithelial layers and different epithelial tissues
is there a complex pattern of cytokeratin expression in gingiva?
yes
can cytokeratin expression change with disease state?
yes= 8 and 18 only in junctional epithelium normally but increase in other epithelium during cancer in mouth
can mutations in cytokeratin genes produce regionally specific diseases?
yes
white sponge nevus- autosomal dominant disorder- mutation in one allele
mutation in cytokeratin 4 and 13- helical region
affects oral non- keratinized epithelia+ nasal mucosa, esophagus, anogenital region
soft white spongy plaques, clinically benigh
epithelial thickening, parakeratosis and vacuolization of suprabasal layers
functional diff between keratinized and nonkeratinized
keratinized tougher
non-keratinized- more flexible
keratinized- more impermeable to outside substances
what is important for mechanical properties of keratinized vs nonkeratinized epithelia?
different cytokeratin types
what are the biochemical properties of cytokeratins in keratinized?
promotes aggregation= form tonofibrils permit binding to with fillagrin- keratohyalin granules- in granular layer superficial layers (keratinized)- very flat cells, dehydrated, no organelles, packed with cytokeratin (tonofibril/fillagrin complexes
what do both non-keratinized and keratinized have in common?
amount of cytokeratin increases in superficial layers
what are the biochemical properties of cytokeratins in nonkeratinized?
cytokeratin type does not [promote aggregation, cant complex with fillagrin
superficiall layers- cells not as flat or dehydrated, retain nuclei +cytokeratin tonofilaments
what accounts for the permeability differences in keratinized and non-keratinized epithelium?
more directly related to other factors instead of type of cytokeratin
desmosomes contribute- more numerous in keratinized epithelia
membrane coating- intercellular permeability barrier
more membrane thickening in keratinized
membrane coating granules
membrane-bound organelles, filled with glycolipids
1st appear in upper prickle cell layers
released in more superficial layers to coat cell
occur in both keratinized and nonkeratinized epithelia and serve as intercellular barrier to aqueous substances
differences in chemical composition creates a more effective barrier in keratinized
membrane thickening
inner face of keratinocytes in upper layers of both non-keratinized and keratinized epithelium
much more pronounced in keratinized epithelium- cornified envelope- 15nm crosslinked protein sheath comprised of loricrin and other proteins instead of phospholipid bilayer
differences in membrane thickening produces a effective paracellular permeability barrier in keratinized epithelium
what is parakeratinized epithelium-
intermediate variant
ex, inflamed gingiva
incomplete keratinization
surface keratin separate from underlying epithelium and fill with fluid
hyperkeratinization
occur in hard palate, smokers- surface layer hypertrophic
what occupies most volume in lamina propria?
ecm
what cells are present in lamina propria
fibroblasts, macrophages, mast cells, other inflammatory cells
what does the ecm composed of?
pgs and gags
glycoproteins (fibronectin)
collagen 1 and 3
elastin
what is the relative amt of type 1: type 3 collagen
greater for less flexible regions of the oral cavity
type 1- hard+rigid ct
type 3- softer ct
what is elastin?
more prominent in oral mucosa than in pulp or pdl
more prominent in lamina propria or of oral mucosa
what is at the epithelial connective tissue interface?
basal lamina- tough ct sheath- separate epithelium and lamina propria.
it is convoluted- contains epithelial rete pegs, connective tissue papillae
papillary layer, reticular layer- deeper layer of lamina propria
resist shear forces on interface- facilitate adhesion between epi and lp
submucosa
2nd layer of ct
present under some regions of oral mucosa
contains larger blood vessels and nerves supplying superficial lp
glands
separates lp from bone and muscle
where is there no submucosa?
tongue- lp to muscle
mucoperiosteum- gingiva, hardpalate next to gingiva, rugae region, median raphe- lp-bone
lining mucosa
non-keratinized or parakeratinized epithelium
buccal and labial mucosa- thick
floor of mouth- thin
lamina propria- fewer collagen fibers and more elastiic fibers
relatively short broad connective tissue papillae
submucosa usually present
attachment to bone or muscle are loose and flexible
clinical implications: incisions more likely to gape and need to be sutured
injections less painful*
masticatory mucosa
keratinized (or parakeratinized)
dense lamina propria
more collagen fibers/fewer elastic fibers than lining mucosa
many long thin connective tissue papillae
submucosa variably present in hard palate, not present in rugae, along midline raphe, adjacent to gingiva
clinical implications- incisions don’t gape, may not require suturing, injections more painfuk
sulcular epithelium
part of free gingiva which faces tooth, generally non-keratinized
junctional epithelium
unique
function- forms seal with hard tissue of tooth (enamel/cementum)
oriented along long axis of tooth
15-30 cells thick at top taper to 3-4 cells thick at bottom
straight basement membrane
keratin expression- simple epithelium
relatively non-differentiated cells, regardless of layer
no tonofilaments, desmosomes, no membrane coating granules= highly permeable
have 2 basal lamina: external (between je/lamina propria)- typical moelcular components
internal (between je and tooth)- integrin and laminin but lacks type 3 and 7 collagen
special laminin seal to tooth
Odontogenic ameloblast associated protein odam
je expresses a protein initially associated with ameloblasts- consistent with its origin from reduced enamel epithelium
not known of function
col
interdental space
characterized by junctional epithelium
can junctional epithelium regenerate?
yes
relatively rapid
occurs around dental implants
vascular supply of gingiva
superior alveolar and palatine- maxillary
inferior alveolar buccal, mental, sublingual- mandibular
goes to pdl, interdental; se[ta and oral mucosa into gingiva
