5. Objectives :
1. Definition
2. Functions
3. Histologic structure of mucosa
A. Keratinized epithelium
B. Non keratinized epithelium
C. Non-keratinocytes
D. Lamina propria
E. Submucosa
6. What is oral mucosa:
• Oral mucosa is the moist mucous
membrane lining the inside of the
mouth.
• It is continuous with skin at the lips, and
from the other side with mucosa of
G.I.T.
• So it shares the characters of both .
7. Functions:
1. Protection:
It acts as a shield protecting
underlying structures from chemical,
thermal and mechanical effects. It
also acts as biological barrier against
bacteria and their toxins.
8. 2. Sensory:
Oral mucosa has several nerve endings
that respond to temp., touch and pain.
Also it provides taste sensation and some
reflexes as swallowing, gagging and
water satisfaction
9. 3. Secretory:
Major and minor salivary
glands open on the surface
so keeps it always moist and
provide washing effect
10. 4.Thermal regulation:
It is mainly obvious in
animals through painting
their skin and evaporation
of saliva.
12. Histologic structure of oral mucosa
• Oral mucosa consists of:
Oral epithelium Lamina propria
Both are separated from each other by basement membrane.
They may be attached directly to underlying structures or through submucosa
13. Oral epithelium
• It is formed of Stratified Squamous Epithelium s.sq.e that either may be
1. Keratinized
2. Non-keratinized
14. 1.Keratinized oral epithelium
Formed of 4 layers named according to the morphology or shape of
cells into:
A. Basal.
B. Spinous.
C. Granular.
D. Keratin.
15. A. Basal cell layer ( stratum basal)
• Single layer of cuboidal cells which have
protoplasmic processes projecting through the
basement membrane termed pedicles.
• Tonofilaments are gathered into bundles to form
tonofibrils. They represent the primary synthetic
product of these cells.
• Basal cells are considered the least differentiated
cells in the oral epithelium.
• They undergo mitosis, one of the daughter cells
remains as progenitor (stem) cells, while the
remaining will differentiate(amplifying).
• They contain a large number organelles indicating
their protein synthetizing activity.
16. 2.Spinous (prickle) cell layer (stratum spinosum)
• Several rows of polyhedral cells.
• The desmosomes seem to bind these
cells together.
• So during histologic preparation the
cells shrink except at the areas where
they are held together by
desmosomes. This gives them the
prickle cell appearance.
17. • They are active protein forming cell contain RER mitochondria, golgi, and
tonofilaments.
• The spinous cells appears larger than the basal ones.
• Desmosomes and tonofilaments form tensile supporting system for the
epithelium against the external pressure.
• Spinous cells are the most active protein synthetizing cells in the oral epithelium.
• The stratum basal and first layers of stratum spinosum are called stratum
germinativum as they give rise to new epithelial cells.
18. • The superficial prickle cell layer and the lower
granular cell layer contain small rounded bodies
called:
• Odland's bodies (keratinosome)
• They are membrane coated granules have
internal lamellate structure.
• They may originate from Golgi app. And RER.
• They are responsible for thickening of cell
membrane which occurs during keratinization.
• They may form on inter cellular agglutinating
material.
19. 3. Granular cell layer (stratum granulosum)
• Several rows of cells, fewer in number and have wider diameter than those in
the spinous layer.
• They contain numerous basophilic keratohyaline granules.
• Those granules are surrounded by ribosomes found in intimate contact with
tonofilaments and are believed to form a matrix that furnishes a medium for
tonofilaments embedding.
• The Odland's bodies are increased and discharged into the intercellular spaces.
• More superficial layer of the granular layer develop a cornified cell envelope
on the inner aspect of their membrane that contribute to the considerable
resistance of the keratinized layer to chemical solvents, one of the major
constituents of this thickening are proteins known as Involucrin, flagirin and
loricrin.
20. • Dramatic changes develop as the cells
approach the keratinous layer. These
include:
1. Disappearance of nuclei,
keratohyaline granules and other
organelles.
2. Decrease in cell size, so the contained
tonofilaments appear tightly packed
3. Tonofilaments are seen embedded in
a matrix possibly derived from the
previously found keratohyaline
granules.
4. The inner unit of the plasma
membrane is thickened. This may be
due to the discharged protein rich in
sulfur which acquire the membrane
highly resistant structure.
21. 4. Keratin layer (stratum cornium)
• Flattened hexagonal discs or squames with
eosinophilic cornified material.
• Orthokeratinized squames show no
organelles and thus, they can no longer form
protein. they are mechanically tough, however,
they desquamate due to abrasion as a result of
alteration of the structure of cell surface and
desmosomes.
• Parakeratinized squames retain pyknotic
nuclei and it is quite often to find other
organelles and the granular layer either
disappeared or cannot be easily distinguished.
22. Desmosomes
• Desmosomes also known as macula
adhaerens, are cell structure specialized
for cell-to-cell adhesion. they are type
of junctional complexes.
• They are localized spot-like adhesions
randomly arranged on the lateral sides
of plasma membranes.
• They form adhesive bonds in a network
that gives mechanical strength to
tissues frequently subjected to
mechanical forces such as epidermis,
oral epithelium and myocardium.
23. Desmosomes
• It is formed of:
• Thickening of 2 adjacent cell
membranes.
• 2 attachment plaques.
• Tonofilaments.
• Intervening extracellular
structure.
24.
25. DESMOSOMES HEMI DESMOSOMES
1- Thickening of 2 cell
membranes
1- Thickening of one cell
membrane
2- Two attachment plaques 2- One attachment plaques
3- Tone filaments 3- Tone filaments
4- Extra cellular adhering
Substance
4- Extra cellular substance
5- Between 2 cells 5- Between cell and basement
membrane
27. 2.Non-keratinized epithelium
• It differs from the keratinized epithelium in
1. where it does not produce keratinous
Layer.
2. lack of granular layer.
3. Epithelial ridges are relatively short and
blunt compared to the narrow and long
ridges in the keratinized epithelium.
4. The non-keratinized epithelium usually
forms a thicker layer than that in the
keratinized epithelium.
28. 1. Basal cells:
• Are morphologically and functionally similar to those in the keratinized epithelium,
however, the intermediate and the superficial cells differ considerably.
2. The intermediate layer:
• The cells are very close to each other and are attached by desmosomes. They are larger
in size than their underlying basal cells and than their counter cells in the keratinized
epithelium.
• The upper cells of the intermediate layer, contain membrane coating granules, but it
differs from that of keratinized epith as they have granular structures rather than the
lamellar ones.
• Non-keratinized epithelium lack granular layer, however, the cells corresponding to
this layer show increase in size, accumulation of glycogen granules and, incomplete
keratohyalin granules.
29. • keratohyaline granules may be related to
internal thickening of the cell membrane.
These granules differ from those found in
keratinized epithelium by exhibiting more
regular and not associated with
tonofilaments.
3. The superficial layer:
• Retain their nuclei, and show interspersed
tonofilaments that do not tend together into
bundles, while the other organelles become
less numerous
30. N.B : all cells of both keratinized or
non-keratinized epithelium are called
keratinocytes.
As these cells can form keratin at any
time.
Example : the cheek mucosa is non-
keratinized, but at the line of meeting
of occlusal surfaces of teeth, there is a
keratinized area called Linea alba.
This keratinization occurs due to
continuous irritation of this area
evoking cells to produce keratin
31.
32. Non-Keratinocytes
Don’t turn into keratinocytes or share in keratin formation
Have a clear halo around the nucleus, and so known, clear cells.
Lack desmosomes except Merkel cells.
Amount to about 10% of the cell population in epithelium.
Not stained with routine H&E stain
Not arranged in rows or sheets, but found scattered in mucosa.
33. 1. Melanocytes (pigment cells)
Site: Basal layer of oral epithelium.
Function: melanin producing cells. They elaborate
melanin pigment in the form of small organelles called
melanosomes, which group to form melanin granules.
Detection: silver impregnation technique or DOPA
reaction and tyrosinase enzyme.
N.B: The number of melanocytes per unit area in the
oral mucosa is constant. In dark race, the melanocytes
are active in synthesizing melanosomes and
transferring them through dendritic processes into the
surrounding epithelial cells, a process referred to as
inoculation.
C.T cells may also demonstrate melanin by DOPA
reaction, These cells are known melanophages, and
may represent macrophages that phagocytosed
melanin from the overlying epithelium.
34. 2. Langerhans cells
• Site: The cells are found in the upper layers of
epidermis and oral epithelium (higher level
cells).
• They have dendritic processes but lack
tonofilaments or desmosomes.
• contain a ch.ch rod bodies termed Langerhans
granules or Berbick granules. Their cell
membrane contains adenosine triphosphatase.
• Function: has been variously described as
regulatory cells controlling epithelial division
and differentiation, as intraepithelial
macrophages, as neural components or as
degenerated melanocytes.
• Detection: gold chloride or CD1a surface
antigen
35. 3.Merkel cells
Site: basal cell layer
No dendritic processes. By e/m they contain sparse
tonofilaments, occasional desmosomes, and a nerve
fiber is immediately subjacent.
These cells contain characteristic membrane
bounded vesicles which may release
neurotransmitter substances across the potentially
synaptic space between the cell and the adjacent
nerve terminal.
Function: neural cells specialized for responding to
touch or pressure stimuli. They are thought to have
slow neuro-secretory activity as their membrane
receptors respond to the stimuli.
Detection: PAS +ve
36. 4. Defensive cells :
Site: Lymphocytes are found at various
epithelial levels in many regions of
clinically normal mucosa. They are
immigrants, found among the epithelial
cells and then infiltrate through
epithelium to reach the surface.
Function: They are involved in
inflammatory response.
Detection: CD3 for T-lymphocytes
CD20 for B-lymphocytes.
37. The inter face between lamina propria and epithelial cells
By L.M: 1-4 m, appears as undulating line as a result of epithelial rete pegs
interdegitate with C.T papilla
• The basal lamina helps to attach and anchor the cells to the underlying
connective tissue.
• The main components of basal lamina are type IV collagen, the glycoproteins
laminin and entacin, and proteoglycans.
• By E/M: three distinct layers of the basal lamina can be described:
• lamina lucida - electron lucent (very little staining in the EM).
• lamina densa - electron dense.
• lamina reticularis - can be associated with reticular fibres of the underlying
connective tissue.
Basement membrane:
40. Lamina propria:
• It is composed of dense connective
tissue of variable thickness which
plays a role in supporting and
securing the nutritional and
metabolic exchange into the
epithelium.
• It may attach the periosteum or
overlay the submucosa.
• Morphologically, the lamina
propria may be divided into two
areas papillary layer and reticular
layer.
41. • The papillary layer:
• has predominantly loose network of
collagen fibers, associated with
reticular fibers.
• The presence of this layer is
dependent on the existence of
epithelial ridges.
• Subjacent to the basement membrane
the fine collagen fibers become
concentrated with reticulin fibers.
• The reticular layer:
• contain closely packed coarse
collagen fibers.
• They are arranged horizontally in the
direction of minimum extensibility to
prevent mucosal deformation.
• Few elastic fibers are found to
restore deformed collagen.
42. Lamina propria is formed of:
• Cells
• Blood vessels
• Lymphatic drainage
• Nerve supply
• Fibers
• All these components are embedded in
amorphous gel-like ground substance
formed of glycoproteins and
proteoglycans
43. SiteFunctionFeaturesCell
Throughout Lamina
propria
Fibers and G.S
formation
Stellate or elongated
with abundant RER
Fibroblast
Throughout L.P.Precursors of
macrophage
Spindle or stellate
shape, dark stained
nucleus contains
many lysosomal
vesicles
Histocyte
Areas of chronic
inflammation
PhagocytosisRounded with pale
staining nucleus
contains lysosome and
phagocytes vesicles
Macrophages
Areas of inflammationPhagocytic, blood,
bone precursor of
macrophage
Rounded with dark
staining kidney shape
Nucleus moderate
amount of cytoplasm
Monocytes
44. SiteFunctionFeaturesCells
Sub epithelialSecrete inflammatory
mediator
as histamine heparin,
serotonin (allergic
reactions)
Rounded or oval with
basophilic granules
Mast cell
Acute inflammationPhagocytosis and cell
killing
Rounded with lobed
nucleus contains
lysosomes and granules
Polymorph nuclear cells
(PMNL)
Acute and chronic
inflammation
Humeral and cell
mediated immunity
Rounded with dark
stained nucleus and
scurry cytoplasm with
some mitochondria
Lymphocyte
Chronic inflammationSynthesis of antibodiesCart wheel nucleus,
eccentric with abundant
RGR in cytoplasm
Plasma cell
Lining vascular charnelsLining blood and
lymphatic channel
Associated with basal
lamina, contain
numerous vesicles
Endothelial cell
45. Blood supply:
Branches of the external carotid artery:
• Superior labial branches of the facial arteries
and infraorbital arteries: Supply blood to the
upper lip
• Inferior branches of the facial arteries and
mental arteries: Supply the lower lip
• Greater and lesser palatine arteries: Supply
the palate
• Sublingual artery: Supplies the sublingual
gland and the floor of the oral cavity
Veins
Veins of the oral cavity generally
follow the arteries and have the
same names.
• The veins of the palate drain
into the pterygoid venous
plexus.
• The lingual veins of the tongue
drain into the internal jugular
vein.
46. The lymphatic drainage of the oral cavity
• Lymph from the upper lip, teeth, lateral parts of the anterior part of the
tongue, and gingiva drains into the submandibular lymph nodes.
• Lymph from the lower lip and apex of the tongue drains into the
submental lymph nodes.
• Lymph from the medial anterior portion of the tongue drains into the
inferior deep cervical lymph nodes, and the posterior portion of the
tongue drains into the superior deep cervical lymph nodes.
47. The nerves of the oral cavity
• Greater and lesser palatine nerves and
nasopalatine nerves (CN V2): Supply
the roof and palate
• Lingual nerve (CN V3): Serves the floor
of the mouth
• Buccal nerve (CN V3): Provides sensory
innervation to the skin and mucosa of
the cheek
• Lingual, palatine, nasopalatine, and
superior alveolar nerves: Supply the
gingiva
48. Nerve supply to the tongue:
• Lingual nerve : touch and temperature (general
sensation) for the anterior two-thirds of the
tongue
• Chorda tympani nerve (CN VII): Part of the
facial nerve; contains taste fibers from the
anterior two-thirds of the tongue.
• Hypoglossal nerve (CN XII): Innervates the
muscles of the tongue (except for the
palatoglossus)
• Glossopharyngeal nerve (CN IX): Supplies
general and taste for the posterior one-third of
the tongue
• Internal laryngeal nerve (CN X): Branches
supply general sensation to a small part of the
posterior part of the tongue
49. Submucosa
• It consists of connective tissue of varying
thickness and density which underlies the
lamina propria.
• The degree of density of submucosa
determines whether the mucosa be firmly or
loosely attached to the underlying
structures.
• It contains fat, salivary glands, blood vessels
and nerves.
• The medium sized arteries branche in the
submucosa and their branches enter the
lamina propria to form subepithelial
capillary plexus.
• The venous and lymphatic drainage occur
through the corresponding vessels that
course back along the rout of arteries.
50. • Sensory nerve fibers in the
submucosa are myelinated, but
they lose their myelin sheath before
branching. The branched fibers
terminate in the lamina propria as
sensory nerve endings of various
organized types, while some
terminate as free nerve endings
which enter the epithelium.
• Unmyelinated visceral nerve fibers
supply the smooth muscles of the
blood vessels and glands.
