Oral mucous membrane

 DEFINITION
 FUNCTIONS
 BOUNDARIES
 TYPES
 CLINICAL FEATURES
 COMPONENTS
 ORAL EPITHELIUM
 KERATINIZATION
 NON KERATINIZATION
 ULTRASTRUCTURE OF THE EPITHELIAL CELL
 CELLULAR EVENTS IN MATURATION
 KERATINIZED EPITHELIUM
 NON KERATINIZED EPITHELIUM
 NON KERATINOCYTES

 JUNCTION OF EPITHELIUM & CONNECTIVE TISSUE
 CELLS
 BLOOD SUPPLY
 NERVE SUPPLY
 KERATINIZED AREAS
 NON KERATINIZED AREAS
 SPECIALISED MUCOSA
 JUNCTIONS IN THE ORAL EPITHELIUM
 AGE CHANGES

The term mucous membrane is used to
describe the moist lining of the:
1. Gastrointestinal tract
2. Nasal passages
3. Other body cavities
that communicate with the external
surface.
In the oral cavity, this lining is referred
to as the oral mucous membrane, or
oral mucosa, which is coated by:
1. Serous secretions
2. Mucous secretions

 DEFENSE
• The integrity of the oral epithelium is an effective barrier for the entry of the
microorganisms.
• These commensal organisms become pathogenic if the host defense is
compromised.
• Infection occurs if the epithelial integrity is broken down resulting in
bacterial invasion or if their toxins are allowed to seep through the
epithelium.
• The oral mucosa is impermeable to bacterial toxins.
• It also secretes antibodies & has an efficient humoral & cell mediated
immunity.

 LUBRICATION
• The secretion of salivary glands keeps the oral cavity moist.
• It prevents the mucosa from drying & cracking thereby ensuring an intact
oral epithelium.
• A moist oral cavity helps in:
1. Speech
2. Mastication
3. Swallowing
4. Perception of taste

 PROTECTION
• It separates & protects deeper tissues & organs in the oral region from the
environment of the oral cavity.
• It shows a number of adaptations of the epithelium & the connective tissue
to withstand:
1. Mechanical forces (compression, stretching, & shearing)
2. Surface abrasions (from hard particles in the diet)

 SENSATION
• In the mouth, receptors respond to:
1. Temperature
2. Touch
3. Pain
4. Pressure
• The tongue uniquely also has taste buds.
• Reflexes such as swallowing, gagging, retching, & salivating also are
initiated by receptors in the oral mucosa.

Oral Cavity
Consists Of Two
Parts
Outer Vestibule
Bounded by the lips
& cheeks
Oral Cavity Proper
Separated from the
vestibule by alveolar
bone & gingiva
POSTERIORLY
Pillars of the fauces &
the tonsils.
SUPERIOR ZONE
The hard & soft
palates.
INFERIOR BORDER
The floor of the mouth
& base of the tongue.

 LINING MUCOSA (60%)
Lip, cheek, vestibular fornix, alveolar mucosa, floor of mouth & soft palate.
• It covers the musculature & is distensible & soft.
• It adapts itself to the contraction & relaxation of cheeks, lips, & tongue & to
movements of the mandible produced by the muscles of mastication.
• It makes up all the surfaces of the mouth except for the dorsum of the
tongue & the masticatory mucosa.

 MASTICATORY MUCOSA (25%)
Gingiva & hard palate.
• The masticatory mucosa is bound to bone & does not stretch.
• It bears forces generated when food is chewed.

 SPECIALISED MUCOSA (15%)
Dorsum of the tongue & taste buds.
• It bears the taste buds, which have a sensory function.

DORSUM OF
THE TONGUE
TASTE BUDS

1. It is continuous with the skin.
2. Deeply colored.
3. Moist surface.
4. Absence of Appendages (hair follicles, sebaceous glands, sweat glands).
5. Smooth surface.
6. NO folds & NO wrinkles.
7. Stippling is present.
8. Lips & Cheeks are Soft & Pliable.
9. Gingiva & Hard Palate are covered by a Firm, Immobile mucosa.
10.Can be Keratinized or Non-Keratinized.

HEALTHY ORAL MUCOSA
A: Attached gingiva, the alveolar & labial mucosa. Gingival stippling is most evident in the interproximal regions. The
mucogingival junction between keratinized gingiva & non-keratinized alveolar mucosa is clearly evident.
B: Vermilion zone adjoining the labial mucosa. Minor salivary gland ducts open to the surface in this region.

The two main tissue components of the oral mucosa are:
1. A stratified squamous epithelium, called the oral epithelium.
2. An underlying connective tissue layer, called the lamina propria.
The interface between epithelium & connective tissue is usually irregular, &
upward projections of connective tissue, called the connective tissue papillae,
interdigitate with epithelial ridges or pegs.
The oral mucosa is separated from underlying tissues by a layer of smooth
muscle & elastic fibers.
In many regions a layer of loose fatty or glandular connective tissue
containing the major blood vessels & nerves that supply the mucosa
separates the oral mucosa from underlying bone or muscle, known as
submucosa.
In regions such as the gingiva & parts of the hard palate, oral mucosa is
attached directly to the periosteum of underlying bone, with no intervening
submucosa. This arrangement is called a mucoperiosteum & provides a firm,
inelastic attachment.

The oral epithelium constitutes the primary barrier between the oral
environment & deeper tissues.
The oral epithelium is a stratified squamous epithelium consisting of cells
tightly attached to each other & arranged in a number of distinct layers or
strata.
The oral epithelium maintains its structural integrity by a process of
continuous renewal in which cells produced by mitotic divisions in the
deepest layers mature & undergo terminal differentiation as they migrate
passively towards the surface to replace those that are shed.
The cells of the epithelium thus can be considered to consist of two functional
populations:
1. A progenitor population (the function of which is to divide & provide new
cells)
2. A maturing population (which continually differentiate or mature to form a
protective surface layer).

EPITHELIAL PROLIFERATION
The progenitor cells are situated in the basal layer in thin epithelia (the floor
of the mouth) & in the lower two to three cell layers in thicker epithelia
(cheeks & palate).
Dividing cells tend to occur in clusters that are more abundant at the bottom
of epithelial ridges than at the top.
A small population of progenitor cells cycles slowly & is considered to
represent stem cells, the function of which is to produce basal cells & retain
the proliferative potential of the tissue.
The larger portion of the progenitor compartment is composed of amplifying
cells, the function of which is to increase the number of cells available for
subsequent maturation.
After cell division, each daughter cell recycles in the progenitor population or
enters the maturing compartment.

Estimating the time necessary to replace all the cells in the epithelium is
known as turnover time of the epithelium & is derived from knowledge of the
time taken for a cell to divide & pass through the entire epithelium.
The turnover time has been estimated at
1. 52 to 75 days in the skin
2. 4 to 14 days in the gut
3. 41 to 57 days in the gingiva
4. 25 days in the cheek
Healing occurs faster in the oral cavity because of increased blood supply &
increased epithelial turnover.

EPITHELIAL MATURATION
These groups of cells, after their origin, become determined & migrate from
the basal layer to the surface to replace the cells that are shed.
Because of this migration, they become part of each layer at every stage.
 The migration of cell from the basal layer to the surface is known as
maturation, & the cells increase in size & shape during this process.
In general, maturation in the oral cavity follows two main patterns:
1. Keratinization
2. Non-Keratinization

The epithelial surface of the masticatory mucosa is:
1. Inflexible
2. Tough
3. Resistant to abrasion
4. Tightly bound to the lamina propria
It is covered by a layer of keratinized cells, & the process of maturation
leading to its formation is called keratinization or cornification.
Example:
1. Gingiva & Hard palate
2. Some regions of specialized mucosa on the dorsum of the tongue
It is of two types:
1. Orthokeratinization
2. Parakeratinization

A: ORTHOKERATINIZATION IN HUMAN GINGIVA
Nuclei are lost in the keratinized surface layer. Keratohyalin granules are visible in the granular layer.
B: PARAKERATINIZATION IN HUMAN GINGIVA
The keratin squames retain their pyknotic nuclei.

The lining mucosa of the oral cavity is:
1. Thicker
2. Shows a different ridge pattern at the connective tissue interface
3. Cells of non-keratinized epithelium are slightly larger
4. The intercellular bridges or prickles are less conspicuous
5. A granular layer is not present
6. The cells of the superficial layer contain nuclei that are often plump
7. This layer does not stain intensely with eosin
Example:
1. Buccal mucosa & Lips
2. Alveolar mucosa
3. Soft palate
4. Underside of the tongue & Floor of the mouth

NONKERATINIZATION IN PRIMATE BUCCAL EPITHELIUM
No clear division of strata exists, & nuclei are apparent in the surface layer.
The differences in thickness & epithelial ridge pattern, as well as in the patterns of maturation, are apparent.

Cells of the basal layer are the least differentiated oral epithelial cells.
They contain typical organelles present in the cells of other tissues as well as
certain characteristic structures that identify them as epithelial cells &
distinguish them from other cell types.
These structures are the filamentous strands called tonofilaments & the
intercellular bridges or desmosomes.
One name often given to an epithelial cell because of its content of keratin
filaments is keratinocyte.
This serves to distinguish these epithelial cells from the nonkeratinocytes.

Keratins represent a large family of proteins of differing molecular weights:
1. The lowest molecular weight are found in glandular & simple epithelia
2. Intermediate molecular weight are found in stratified epithelia
3. The highest molecular weight are found in keratinized stratified epithelia
Thus all stratified oral epithelia possess keratins 5 & 14, but differences
emerge between:
1. Keratinized oral epithelium (which contains keratins 1, 6, 10, & 16)
2. Non-keratinized epithelium (which contains keratins 4, 13, & 19)
An important property of any epithelium is its ability to function as a barrier,
which depends to a great extent on the close contact or cohesiveness of the
epithelial cells.

Cohesion between cells is provided by a viscous intercellular material
consisting of protein-carbohydrate complexes produced by the epithelial cells
themselves.
In addition, modifications of the adjacent membranes of cells occur, the most
common of which is the desmosome or macula adherens, into which bundles
of intermediate filaments (tonofilaments) insert.
Adhesion between the epithelium & connective tissue is provided by
hemidesmosomes, which attach the cell to the basal lamina.
Like desmosomes, hemidesmosomes also possess intracellular attachment
plaques with tonofilaments inserted into them.
Tonofilaments, (hemi) desmosomes, & basal lamina together represent a
mechanical linkage that distributes & dissipates localized forces applied to
the epithelial surface over a wide area.

Two other types of connection are seen between cells of the oral epithelium:
1. Gap junctions
2. Tight junctions
The gap junction is a region where membranes of adjacent cells run closely
together, separated by only a small gap.
Small interconnections are apparent between the membranes across these
gaps.
Such junctions may allow electrical or chemical communication between the
cells called communicating junctions, which are seen occasionally in oral
epithelium.

In both types of epithelia the changes in cell size & shape are accompanied
by:
1. Synthesis of more structural protein in the form of tonofilaments
2. The appearance of new organelles
3. The production of additional intercellular material
A number of changes, however, are not common in both epithelia & serve as
distinguishing features.

PRINCIPAL STRUCTURAL FEATURES OF EPITHELIAL CELLS IN SUCCESSIVE LAYERS
A: Orthokeratinized oral epithelium. B: Non-keratinized oral epithelium.

LOW-MAGNIFICATION ELECTRON MICROGRAPHS OF PRICKLE CELLS FROM
(A) Keratinized gingival epithelium (B) Non-keratinized buccal epithelium
Filaments are assembled into distinct bundles (tonofibrils) in the keratinized tissue but are inconspicuously dispersed
in the non-keratinized epithelium.

Keratinized epithelium has four cell layers which are named on the basis of
their morphological appearance as follows:
1. Basal layer (Stratum Basale)
2. Spinous layer (Stratum Spinosum)
3. Granular layer (Stratum Granulosum)
4. Cornified layer (Stratum Corneum)

STRATUM BASALE
The basal layer is a single layer of cuboidal or columnar cells adjacent to the
lamina propria, separated from it by basal lamina.
The cells of the basal layer are the least differentiated among the oral
epithelial cells.
Mitotic activity is prominent in this layer as new cells are formed here.
The term parabasal is used to refer to the innermost layer of stratum
spinosum adjacent to the basal layer.
The basal cell layer & parabasal spinous cells are often described as stratum
germinativum.
The cells of the basal layer show intracellular organelles associated with
synthesis & secretion of proteins such as ribosomes, rough endoplasmic
reticulum, mitochondria, Golgi apparatus & also tonofilament of keratin,
reflecting their epithelial nature.

Hemidesmosomes are specialized structures seen in relation to the cells of
the basal layer & their surface facing the basal lamina.
These structures provide adhesion between the epithelium & the connective
tissue.
Desmosome is another structure seen on the lateral side of the adjacent
basal cells.
This provides close contact or cohesion between the cells of the basal layer.
Both the desmosomes & hemidesmosomes have attachment plaques to
which the tonofilaments (intermediate filaments arising from the cytoskeleton)
arising from basal cells are attached.

STRATUM SPINOSUM
The spinous layer is above the basal layer & is made up of several rows of
polyhedral cells.
The cells are larger & more rounded than those of the basal layer.
The cells of this layer exhibit prominent intercellular bridges—the
desmosomes—which give the cells a prickly appearance.
Tonofibrils are cytoplasmic protein structures in epithelial tissues that
converge at desmosomes & hemidesmosomes.
The tonofibril network & desmosomes make up the tensile supporting system
for the epithelium.
During tissue preparation, the cells shrink away from each other & remain in
contact only at points (due to the desmosomes anchoring the cells together).

This gives the cells a spiny appearance.
Involucrin, a precursor protein of the cornified envelope, is present in this
layer.
However, there is a progressive decrease in protein synthetic activity through
the layer.
In the upper part of the spinous layer, the cells show spherical, membrane-
coating granules closely associated with the cell membrane, called
keratinosome, lamellar granule or Odland body.

PHOTOMICROGRAPH OF THE PRICKLE CELL LAYER OF GINGIVAL EPITHELIUM
The clear cells (arrowheads) have dark nuclei surrounded by a light halo

A: Light micrograph showing the granular cell layer whose cells contain keratohyaline granules, & the prickle cell layer
in keratinized oral epithelium the intercellular bridges (prickles, arrowheads) between adjacent cells.
B: Electron micrograph; in this oral epithelium preparation, minimal shrinkage has occurred so that cells are closely
apposed, & the numerous desmosomes holding the cells together are clearly seen. A clear specialized intercellular
zone (arrows) can be seen between the attachment plaques into which tonofilaments insert.

STRATUM GRANULOSUM
The cells of the granular layer show more maturation than those of the basal
& prickle cell layers.
The cells are flatter, wider & larger than spinous cells with less organelles &
more tonofilaments.
The most prominent finding is the presence of a large number of small,
basophilic granules, called keratohyaline granules (which stain blue with
haematoxylin & eosin).
The nuclei show signs of degeneration & pyknosis.
Proteins are still synthesized but at a reduced rate.
The keratohyaline granules contain profilaggrin (precursor of the protein
filaggrin) which plays an important role in binding keratin filaments together.

ELECTRON MICROGRAPHS OF KERATOHYALINE GRANULES IN ORAL EPITHELIUM
A: From the granular layer, irregularly shaped granules are associated intimately with tonofilaments.
B: A granule of the type occasionally seen in non-keratinized oral epithelium is regular in shape but is not associated
with tonofilaments.

The membrane coating granules, also seen in the upper spinous layers,
discharge their lipid-rich contents into the intercellular space.
They act as a cementing substance & contribute to the permeability barrier of
this layer.
Synthesis of proteins such as involucrin & loricrin helps increase the
thickness of the cell membrane, thus forming a resistant cornified cell
envelope.

ELECTRON MICROGRAPHS OF MEMBRANE COATING GRANULES IN ORAL EPITHELIUM
A: Elongated lamellate type seen in keratinized epithelium
B: Circular type with a dense core found in non-keratinized

STRATUM CORNEUM
The cornified layer represents the final stage in the maturation of the
Epithelial cells.
The cells of this layer, termed squames, are larger & flatter than the granular
cells.
They are devoid of nuclei, organelles & Odland keratohyaline granules
because of the release of proteases within the cell (autolysis).
The cells consist of closely packed tonofilaments coated by protein filaggrin
(protein of keratohyaline granules).
This is collectively called keratin.
It is strongly cross-linked by disulphide bonds which give mechanical &
chemical resistance.
This layer is histologically amorphous & acidophilic.

As the desmosomes become weaker & disappear, the cells of this layer
desquamate or shed, necessitating the constant turnover of epithelial cells.
Para-keratinization is seen in some parts of the oral cavity, such as the
gingiva & parts of the hard palate.
Here, the cells retain the pyknotic or shrunken nuclei or partially lysed
organelles till they desquamate.

This epithelium is composed of the following three layers:
1. Stratum Basale
2. Stratum Intermediate
3. Stratum Superficial
As in keratinized epithelium, the non-keratinized epithelial cells enlarge &
become flatter as they move towards the surface.
The basal cell layer resembles that of the keratinized epithelium.

The cells of the stratum intermedium are larger than those of the stratum
spinosum, & their cell surfaces are more closely applied with a less-
prominent intercellular bridge & hence lack the prickly appearance.
The granular layer is not present, & the cells above stratum intermedium lack
keratohyaline granules & filaggrin & have less-developed tonofilaments.
The membrane- coating granules are smaller than those of the keratinized
epithelium & account for the greater permeability of the non-keratinized
epithelium.
The cells of the superficial layer contain nuclei & have more organelles when
compared with the cells of the stratum corneum.
The superficial layer lacks keratin filaments & does not stain intensely with
eosin, unlike keratinized epithelium.

About 10% of the cells of the oral epithelium are non-keratinocytes as they
do not have the ability to keratinize.
These cells include:
1. Melanocytes
2. Langerhans cells
3. Merkel cells
4. Inflammatory cells
These cells lack desmosomal attachments with the adjacent cells (except the
Merkel cell).
The cytoplasm shrinks around the nucleus to produce a clear halo during the
histologic preparation, thus, they are also called clear cells.

MELANOCYTES
They are pigment (melanin)-producing cells derived from the neural crest.
They migrate into the basal layer of the epithelium.
They are thought to be long, living cells that are self-replicating.
They lack tonofilaments & desmosomes but have long branching dendritic
processes that extend in several directions & across several layers of
epithelium.
Each melanocyte establishes contact with 30–40 keratinocytes through its
dendritic process.
Melanin is synthesized by melanocytes using the enzyme tyrosinase.
It is packed in small granules called melanosomes that are transferred into
the cytoplasm of the adjacent keratinocytes through the dendritic process.

MELANIN PIGMENTATION OF THE ATTACHED GINGIVA IN A
DARK-SKINNED INDIVIDUAL

Sometimes, the melanin pigment can be dispersed in the connective tissue
where it is taken up by the macrophages, termed melanophages.
Melanocytes appear as clear cells in the haematoxylin section & have a
spider-like appearance with silver stain (dendritic cell).
Variation is seen in the location of the melanin pigment in the oral cavity.
The gingiva, buccal mucosa, hard palate & tongue are the regions where
melanin pigmentation is commonly seen.
The degree of pigmentation does not depend on the number of melanocytes
but relies on various factors such as size of the melanosomes, the degree of
dispersion & melanization of melanosomes & the rate of degradation of the
pigment.

LANGERHANS CELLS
Langerhans cell is a clear or dendritic cell derived from the bone marrow.
It leaves the bloodstream, enters the lamina propria & penetrates the basal
lamina to reach the epithelium.
This migration is related to the release of chemokines by the keratinocytes to
the surface receptors on the Langerhans cells.
These cells are seen in the upper layer of oral epithelium.
Under a light microscope, these cells appear as clear cells due to the lack of
desmosomes.
Ultrastructurally, these cells have vacuolated nucleus & characteristic rod- or
flask-shaped granules called Birbeck’s granules.

Langerhans cells have an immunologic function as antigen-presenting cells.
 They recognize antigens entering the epithelium from the external
environment & engulf them.
Intracellular lysosomes present in the Langerhans cells split the antigens into
peptide components.
These fragments are then transferred & presented to the T-lymphocytes
either locally or at the lymph nodes.
It is suggested that as the Langerhans cells migrate from the epithelium to
the regional lymph nodes to present the fragments of the antigen to the
lymphocytes, they help the epithelium of the oral mucosa interact with the
entire lymphoid system to mount an immune response.

MERKEL CELLS
These are seen in the basal layer close to nerve fibres.
Merkel cells respond to touch sensation.
These cells are not dendritic.
They occasionally possess keratin filaments & desmosomes & hence do not
appear as clear cells histologically.
Ultrastructurally, these cells have a nucleus which shows deep invagination &
a characteristic rodlet appearance.
The other characteristic finding is the presence of small, membrane-bound
granules in the cytoplasm which are seen in close proximity to the nerve fibre
associated with the cell, which generates an impulse.
These cells are more commonly seen in masticatory mucosa such as the
gingiva.

INFLAMMATORY CELLS
A number of inflammatory cells can be seen in various layers of epithelium.
The most common among them are the lymphocytes which are closely
associated with the Langerhans cells.
These inflammatory cells are transient & do not reproduce themselves in the
epithelium like other non-keratinocytes.

The interface between the epithelium & the connective tissue is an undulating
surface where the papillae of the connective tissue interdigitate with the
epithelial ridges.
This undulating arrangement makes the interface larger than a simple flat
junction & does the following:
1. Provides better attachment
2. Enables external forces applied to the epithelium to be dispersed over a
wider area of connective tissue
3. Provides a wider area for metabolic exchange between the epithelium & the
connective tissue

Under a light microscope, this interface appears 1–2 μm thick & stains
positively with periodic acid–Schiff stain & is termed basement membrane.
Ultrastructurally, it is called the basal lamina & is made of three layers:
1. Lamina lucida is a clear zone just below the epithelial cells
2. Lamina densa is the middle of the three layers
3. Lamina fibroreticularis is located adjacent to lamina propria & contains fine
reticular fibres
All the layers of basal lamina except the components of lamina fibroreticularis
are thought to be derived from the epithelium.

The basal cells of the epithelium are not directly attached to the connective
tissue but form mechanical adhesions with basal lamina through attachments
called hemidesmosomes.
The basal lamina is composed of a network of type IV collagen in which
proteoglycan & glycoprotein molecules such as laminin & fibronectin are
found.
Other proteins such as integrins & bullous pemphigoid antigens strengthen
the bond between the basal cell & the basal lamina.
Fine anchoring fibrils of type VII collagen bind to the type IV collagen of the
basal lamina.

LAMINA PROPRIA
Lamina propria is the connective tissue of variable thickness present
immediately below the epithelium, supporting it.
It is divided into:
1. The papillary layer is made up of finger-like projections of the connective
tissue which extend deep into the epithelium & interdigitate with the
epithelial ridges. The number, length & width of these papillae vary in
different parts of the oral cavity. In areas of masticatory mucosa, there is an
increase in the length & number of papillae, whereas in the areas of lining
mucosa, the papillae may be short or absent. The papillary layer is made up
of loosely arranged, thin collagen fibres.
2. The reticular layer is below the papillary layer & is always present. It is
made up of thick collagen fibres which are arranged in bundles.

The lamina propria consists of cells, fibres & blood vessels embedded in
ground substance.
In addition to fibroblasts, macrophages, mast cells & inflammatory cells are
seen.
The extracellular matrix is composed of collagen fibres mainly of type I (90%)
& type III (8%).
A small amount of elastic fibres is present which do not form bundles like
collagen fibres.
The ground substance is composed of proteoglycans & glycoproteins.
The blood supply comes from the plexus of large vessels in the submucosa
or from the deeper part of the reticular layer.
These give rise to small branches which form a capillary plexus between the
papillary & the reticular layer.

JUNCTION BETWEEN EPITHELIUM & CONNECTIVE TISSUE

SUB MUCOSA
Submucosa is the connective tissue of varying thickness which serves to
attach the lamina propria to the underlying bone or muscle.
The structure of the submucosa decides the nature of attachment, whether
loose or firm.
While the submucosa is prominent in some parts of the oral cavity such as
cheeks, lip & parts of the palate, it is less prominent or absent in some other
parts.
The lamina propria is directly attached to the bone tightly in the areas devoid
of submucosa.
In such cases, the epithelium & the lamina propria are collectively referred to
as mucoperiosteum.
The submucosa contains large blood vessels, nerves & lymphatics.
Adipose tissue & minor salivary glands are also seen in the submucosa.

A: Photomicrograph of palatal mucosa showing the approximate boundaries of the papillary & reticular layers. The
group of minor salivary glands in the submucosa is apparent.
B: Higher magnification in the region of the reticular layer showing cells, mostly fibroblasts, & densely packed collagen
bundles.

CYTOKERATINS
The cytoskeleton of all epithelial cells is made up of microfilaments,
microtubules & cytokeratins.
1. Microfilaments: 4–6 nm in diameter
2. Cytokeratins are called intermediate filaments: 7–11 nm in diameter
3. Microtubules: 25 nm in diameter
Cytokeratins are important in maintaining the shape of the cell & also function
as stress-bearing structures.
They are seen in contact areas like in desmosomes & hemidesmosomes.
There are about 20 types of cytokeratin which are classified as :
1. Type I
2. Type II

MICROFILAMENTS
A: Cultured osteogenic cells labeled with fluorescent rhodamine-phalloidin for actin, the main protein constituting
microfilaments (nuclei are stained using 4,6-diamino-2-phenylindole [DAPI] & appear blue).
B: Nomarski differential interference contrast image of microfilament bundles appearing as elongated raised lines in
the cytoplasm of cultured fibroblasts.
C: Electron micrograph of microfilaments in the cytoplasm of a fibroblast.

A: Intermediate filaments, consisting of vimentin polymers, in Saos osteogenic cells revealed by immunofluorescence.
B: Electron micrographs of intermediate filaments, consisting of cytokeratins, in epithelial cells; these form discrete
bundles called tonofilaments (Tf) that insert into the desmosomal plaques (DS) or distribute around the periphery of a
cell.

MICROTUBULES
A: Fluorescent micrograph of cultured osteogenic cells labeled with an antibody to tubulin, the main protein of
microtubules.
B & C, Electron micrographs of longitudinally oriented (B) cross-sectioned (C) microtubules (arrowheads).

CELL
TYPE
MORPHOLOGIC CHARACTERISTICS FUNCTION DISTRIBUTION
FIBRO-
BLAST
Stellate or elongated with abundant
rough endoplasmic reticulum
Secretion of fibers &
ground substance
Throughout
lamina propria
HISTIO-
CYTE
Spindle-shaped or stellate;
often dark staining nucleus;
many lysosomal vesicles
Resident precursor
of functional
macrophage
Throughout
lamina
propria
MACRO-
PHAGE
Round with pale-staining nucleus;
contains lysosomes & phagocytic
vesicles
Phagocytosis,
including antigen
processing
Areas of chronic
inflammation
MAST
CELL
Round or oval with basophilic
granules staining meta-
chromatically
Secretion of certain
inflammatory
mediators &
vasoactive agents
Throughout
lamina propria;
often sub-
epithelial

CELL TYPE MORPHOLOGIC CHARACTERISTICS FUNCTION DISTRIBUTION
NEUTRO-
PHIL
Round with characteristic lobed
nucleus; contains lysosomes &
specific granules
Phagocytosis & cell
killing
Areas of acute
inflammation
within lamina
propria; may be
present in
epithelium
LYMPHO-
CYTE
Round with dark-staining nucleus &
scant cytoplasm with some
Mitochondria
Some lymphocytes
participate in
humoral or cell-
mediated immune
response
Areas of acute &
chronic
inflammation
PLASMA
CELL
Cartwheel nucleus;
intensely basophilic cytoplasm with
abundant rough endoplasmic reticula
Synthesis of
immunoglobulins
Areas of chronic
inflammation,
often peri-
vascularly
ENDO-
THELIAL
CELL
Normally associated with a basal
lamina; contains numerous
pinocytotic vesicles
Lining of blood &
lymphatic channels
Lining vascular
channels
throughout
lamina propria

SUPERIOR LABIAL ARTERY
ANTERIOR: ANTERIOR SUPERIOR AVEOLAR ARTERY
LINGUAL: MAJOR PALATINE ARTERY
BUCCAL: BUCCAL ARTERY
POSTERIOR: POSTERIOR SUPERIOR ALVEOLAR ARTERY
MAJOR PALATINE ARTERY
NASOPALATINE ARTERY
SPHENOPALATINE ARTERY
MINOR PALATINE ARTERY
BUCCAL ARTERY
SOME TERMINAL BRANCHES OF FACIAL ARTERY
POSTERIOR ALVEOLAR ARTERY
INFRAORBITAL ARTERY

INFERIOR LABIAL ARTERY
MENTAL ARTERY
BRANCH OF INFERIOR ALVEOLAR ARTERY
ANTERIOR BUCCAL : MENTAL ARTERY
ANTERIOR LINGUAL : INCISIVE & SUBLINGUAL ARTERY
POSTERIOR BUCCAL : INFERIOR ALVEOLAR & BUCCAL ARTERY
POSTERIOR LINGUAL : INFERIOR ALVEOLAR & SUBLINGUAL ARTERY
SUBLINGUAL ARTERY
BRANCH OF LINGUAL ARTERY
ANTERIOR TWO THIRDS : DEEP LINGUAL ARTERY
POSTERIOR THIRDS : DORSAL LINGUAL ARTERY, TO BASE OF
TONGUE,ABOUT POSTERIOR THIRD

Twigs from infraorbital branch of maxillary nerve
Anterior, posterior, & middle superior alveolar branches of maxillary nerve
Greater, lesser, & sphenopalatine branches of maxillary nerve
Lesser palatine branch of maxillary nerve, tonsillar branch of glossopharyngeal nerve,
& nerve of pterygoid canal
Twigs from infraorbital branch of maxillary nerve, superior alveolar branch of maxillary
nerve, buccal branch of mandibular nerve, & possibly some terminal branches of facial
nerve

HARD PALATE
The hard palate is concave & the space is mostly filled by tongue at rest.
The anterior two third of the palate has a bony skeleton formed by the
palatine processes of the maxilla & the horizontal plates of the palatine bone.
The mucous membrane is tightly fixed to the underlying periosteum &
therefore immovable.
It is pink in colour.
The incisive fossa is a depression in the midline of the bony palate posterior
to the central incisor teeth into which the incisive canals open.
The mucosa of the hard palate is a masticatory mucosa with ortho- or para-
keratinized epithelium.
The mean turnover time of hard palate cells is 24 days.

The submucosa in the lateral regions of the anterior palate is composed of
fatty tissue & that in the posterior palate is composed of palatine glands.
In the centre of the palate, there is no submucosa & the connective tissue is
directly adherent to the underlying periosteum of the bone termed median
raphae.
Rugae are a series of elevated ridges that appear in the anterior region of the
hard palate on each side of the median raphae & behind the incisive papilla.
With the increase in the size of the anterior part of the palate in the early
years of life, the length of the rugae & the distance between each elevation
increase.
The number of rugae on each side of the palate varies between three & five.
The palatine rugae do not extend posteriorly beyond the anterior half of the
hard palate & they never cross the midline.

PHOTOMICROGRAPH OF THE JUNCTION BETWEEN MUCOSA COVERING THE HARD & THE SOFT PALATE.
The difference in thickness & the ridge pattern between keratinized epithelium of the hard palate & non-keratinized
epithelium of the soft palate is apparent. The section has been stained by the van Gieson's method to demonstrate
collagen; the lamina propria of the hard palate contains thick dense bundles, whereas collagen forms thinner fibers in
the soft palate. Minor salivary glands occur beneath the mucosa.

Rugae are folds of epithelium with dense connective tissue.
The anterior rugae are more apparent than the posterior ones.
The rugae pattern is not bilaterally symmetrical.
They are easily palpated & can be felt by the tongue.
The following zones can be distinguished:
1. Gingival region, adjacent to the teeth
2. Palatine raphe, also known as the median area, extending from the incisive
papilla posteriorly
3. Anterolateral area or fatty zone between the raphe & gingiva
4. Posterolateral area or glandular zone between the raphe & gingiva.

֎RUGOSCOPY
Rugae are unique in each individual like fingerprints & can be used to identify
individuals for forensic purposes.
The analysis of rugae pattern is called rugoscopy.

֎LOCAL ANAESTHESIA INFILTRATION INTO MASTICATORY MUCOSA
Infiltration of local anaesthesia into masticatory mucosa is very difficult
because of the firm attachment of mucosa to the underlying bone, whereas in
lining mucosa, infiltration is easy as the fluid gets dispersed fast without
causing much pain.

GINGIVA
It covers the alveolar process of the jaws & surrounds the necks of the teeth.
It protects the underlying tissues of the tooth attachment from the oral
environment.
It disappears when teeth are extracted.
The gingiva can be anatomically divided into:
1. Marginal gingiva
2. Attached gingiva
3. Interdental gingiva

1. MARGINAL GINGIVA/FREE GINGIVA/UNATTACHED GINGIVA
This is the terminal visible edge of the gingiva, about 1–2 mm wide,
surrounding the tooth in a collar-like fashion.
The surface of the gingival margin is smooth, in contrast to that of the
attached gingiva, from which it is demarcated by an indentation called free
gingival groove.

2. ATTACHED GINGIVA/FUNCTIONAL MUCOSA
It is a band of keratinized mucosa measuring 3–12 mm in width.
It is bound to the underlying periosteum of the alveolar bone.
The mean turnover time for the attached gingival tissue is 10 days.
• Extensions:
1. Coronally: Free gingival groove.
2. Apically: Mucogingival junction, a junction between the attached gingiva &
the alveolar lining mucosa.
• Width of the Attached Gingiva: It ranges from 1 to 6 mm. It is greatest in
the mandibular posterior lingual aspect & narrowest in the buccal aspect of
the third molar region of the mandible.

3. INTERDENTAL GINGIVA
The papilla assumes its shape on the basis of the contact relationships
between the teeth, the width of the approximating tooth surfaces & the course
of the cement-enamel junction.
In the anterior dentition, the interdental papillae are of a pyramidal form, while
in the posteriors, especially in molars, they are more flattened in the bucco-
lingual direction.
Because of the presence of the interdental papillae, the marginal gingiva
follows a more noticeable scalloped outline throughout the dentition.

֎GINGIVAL ATTACHMENT
The level of attachment of gingiva is an important factor to be considered
while placing restorations.
The clinical crown is smaller than the anatomical crown in the case of young
individuals; as a result, tooth preparation & crown placement are difficult.
The restoration has to be replaced later when recession takes place.

֎GINGIVAL RECESSION
It causes exposure of cementum.
As cementum is softer than enamel, it wears off easily resulting in abrasion &
root caries.

COL
The posterior teeth have approximating contact surfaces rather than contact
points.
The interdental gingiva has a shape in conformity with the outline of the
interdental contact surfaces; a concavity, col, is established in the premolar &
molar regions.
The interdental papillae have a facial portion & a lingual or a palatal portion
separated by a col region.
Col is non-keratinized & shares many features with those of junctional
epithelium.

GINGIVAL SULCUS OR CREVICE
The gingival sulcus is an area of potential space between a tooth & the
surrounding gingival tissue & is lined by sulcular epithelium.
In healthy gingival conditions, the gingival sulcus ranges from 0.5 to 3 mm in
depth.
The clinical depth of this sulcus beyond 3 mm is considered a pathologic
deepening which is termed periodontal pocket.
The inner surface of the sulcus facing the tooth is lined by the sulcular
epithelium, which is normally non-keratinized.

Sagittal section through the oral
cavity of a human embryo
showing the tongue, floor of the
mouth, alveolar bone ridge with
a tooth bud, & lip. Differences
in thickness are already
apparent between the epithelia
of the labial mucosa, alveolar
ridge, floor of the mouth, &
tongue; however, keratinization
has not yet begun.

JUNCTIONAL EPITHELIUM
It is a highly specialized epithelial tissue which divides faster than any other
normal epithelium.
The mean turnover time of junctional epithelium is 2–6 days.
The junctional epithelium is basically a stratified, squamous, non-keratinizing
epithelium comprising two layers: basal & suprabasal layers.
The junctional epithelium differs from the gingival oral epithelium & sulcular
epithelium in origin & structure.
This specialized epithelium ranges in thickness from few cells at its most
apical portion to between 15 & 30 cells at its most coronal portion adjacent to
the sulcular epithelium, & the cells align themselves in a plane parallel to the
tooth surface.
The length of this epithelium is approximately 0.25–1.35 mm.

The unique feature of this epithelium is that it exhibits two basal laminas
which are derived from the basal cells situated away from the tooth surface:
1. External basal lamina: The basal cells rest on the external basal lamina
that interfaces with the connective tissue, as in any other epithelium.
2. Internal basal lamina: Suprabasal cells have a similar appearance &
maintain actual attachment of gingiva to the tooth surface by means of the
structural complex, internal basal lamina. The internal basal lamina is
distinctive because it binds to calcified surfaces rather than connective
tissues.
The cells of the basal layer proliferate rapidly while those of the suprabasal
layer have no mitotic activity.
The epithelium & connective tissue interface is not characterized by rete
ridges & tends to be straight with only mild undulations present in more
coronal portions.

Epithelium has wide intercellular gaps, larger than those in either sulcular or
oral epithelium.
Hence, even in healthy gingiva, numerous polymorphonuclear leukocytes are
evident.
During inflammatory conditions, the numbers of these cells increases
dramatically.
Lymphocytes are also found inside the epithelial lining in the junctional
epithelium.
The junctional epithelium exhibits several characteristic features such as
acting as a barrier against plaque bacteria & allowing access of gingival fluid,
inflammatory cells & components of the immunologic host defence to the
gingival margin.
It also possesses a rapid turnover contributing to the host–parasite
equilibrium & repair of injured tissue.

A: An electron micrograph of junctional epithelium (JE) showing the attachment to the enamel surface at the internal
basal lamina (IBL) & to the connective tissue (CT) by the external basal lamina (EBL). The lack of differentiation of the
epithelium & the wide intercellular spaces are notable. ES, Enamel space.
B: An electron micrograph showing the fine structure of the attachment of a junctional epithelial cell to the enamel
surface via the internal basal lamina. Hemidesmosomes (HD) are evident at the surface of the cell.

DEVELOPMENT OF THE JUNCTIONAL EPITHELIUM
The enamel of the unerupted, fully formed crown is covered by a few layers
of flattened cuboidal cells called reduced enamel epithelium.
Normally, it terminates at the cementoenamel junction.
At this early stage, the epithelial attachment to the crown surface is by means
of hemidesmosomes.
When the tooth breaks through the oral mucosa, the reduced enamel
epithelium fuses with the oral epithelium & is converted into the junctional
epithelium, forming a collar around the fully erupted tooth.
Concurrently, gingival sulcus is also formed.
This process takes 1–2 years to get completed.
The junctional epithelium, like all squamous epithelia, is a continually
renewing structure with epithelial cells moving coronally to be shed off at the
free surface into the base of the sulcus.

MIGRATION OF THE JUNCTIONAL EPITHELIUM
The position of the junctional epithelium varies with different stages of
eruption.
During the initial stages of eruption, the junctional epithelium covers most of
the crown portion of the tooth.
Once the tooth reaches the occlusal plane, the junctional epithelium covers
about one-fourth of the crown.
At this stage, the clinical crown is smaller than the anatomical crown.
As age increases, the junctional epithelium migrates to the cementoenamel
junction, placing the clinical & the anatomical crown at the same level.
In older age, it migrates to the cementum exposing the roots leading to a
larger clinical crown.

This process occurs due to the detachment of the basal layer of cells.
This basal layer of cells further get reattached at a more lower/apical level.
The process of migration of junctional epithelium happens physiologically
without any degeneration.
During the presence of inflammation, the apical migration occurs faster,
which results in a periodontal pocket.

SULCULAR EPITHELIUM
It extends between the oral epithelium & the junctional epithelium, from the
coronal limit of the junctional epithelium to the crest of the gingival margin, &
lines the gingival sulcus.
It is a thin, non-keratinized, stratified, squamous epithelium with more folded
rete pegs as compared with the junctional epithelium.
This epithelium is less permeable compared with the junctional epithelium.
Unlike the junctional epithelium, this contains fewer inflammatory cells,
primarily neutrophils.

STIPPLING
The surface of the gingiva is characterized by an ‘orange peel’ appearance
known as stippling which reflects the contour of the epithelial connective
tissue boundary in healthy gingiva.
Stippling can be described as fine or coarse as it varies with age & gender.
The evidence of stippling starts at the age of 2–3 years, & its absence has
been described as normal in older ages.
It is obliterated as part of the early signs of inflammation.

VERMILION ZONE
The vermilion zone, situated between the labial mucosa & the skin of the lip,
has a structure different from the skin or the mucosa.
While the skin is covered by a thick keratinized epithelium, the vermilion zone
has a thin keratinized epithelium, which is translucent due to the increased
presence of eleidin.
The lamina propria has long papillae & carries capillaries close to the
surface.
The close proximity of the blood vessels to the surface along with thin
transparent epithelium gives this zone a red colour that is characteristic of the
humans.
As this zone is exposed to atmosphere & the submucosa is devoid of
mucous glands, it dries up easily & requires moistening with saliva by the
tongue.

FEATURES GINGIVA HARD PALATE VERMILION ZONE
COVERING
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
EPITHELIAL
THICKNESS
THICK THICK THIN
TYPE OF
KERATINIZATION
ORTHO-
KERATINIZATION
OR
PARAKERATINIZATION
ORTHOKERATINIZED,
OFTEN
PARAKERATINIZED IN
PARTS
ORTHO-KERATINIZED

FEATURES GINGIVA HARD PALATE VERMILION ZONE
TYPES OF FIBRES
PRESENT
Collagen fibers
Presence of thick
collagen fibers forming a
dense tissue especially
in the rugae region
Collagen & some elastic
fibres
STRUCTURE OF
PAPILLA
Narrow papillae Long papillae Many narrow papillae
VASCLARITY
Highly vascular but
presence of long
capillary loops showing
anastomoses
Moderate vascular
supply with short
capillary loops
Capillary loops close to
surface in papillary layer
ATTACHMENT
TO UNDERLYING
STRUCTURE
Absence of mucosa;
Mucosa firmly attached
by collagen fibers to the
periosteum of alveolar
Dense collagenous
connective tissue
attaches the mucosa to
periosteum
Firm attachment to
underlying muscle

FEATURES
LABIAL &
BUCCAL
MUCOSA
ALVEOLAR
MUCOSA
FLOOR OF THE
MOUTH
SOFT PALATE
VENTRAL
SURFACE OF
TONGUE
COVERING
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
STRATIFIED
SQUAMOUS
EPITHELIUM
EPITHELIAL
THICKNESS
VERY THICK THIN VERY THIN THIN THIN
TYPE OF
KERATINI-ZATION
NON-
KERATINIZED
NON-
KERATINIZED
NON-
KERATINIZED
NON-
KERATINIZED
NON-
KERATINIZED

FEATURES
LABIAL &
BUCCAL
MUCOSA
ALVEOLAR
MUCOSA
FLOOR OF THE
MOUTH
SOFT PALATE
VENTRAL
SURFACE OF
TONGUE
TYPES OF
FIBRES
PRESENT
Collagen & elastic
fibres
Elastic fibres
Collagen & few
elastic fibres
Many elastic
fibres forming an
elastic lamina
Collagen & some
elastic fibres
STRUCTURE OF
PAPILLA
Long slender
papillae
Short papillae Short papillae Short papillae Short papillae
VASCLARITY
Rich
anastomosing
capillary loops
into papillae
Capillary loops
close to the
surface supplied
by superficial
periosteal vessels
Highly vascular
with short
anastomosing
capillary loops
Rich in vascularity
with well
developed
capillary network
Capillary network
in sub-papillary
layer, reticular
layer
comparatively
avascular
ATTACHMENT
TO
UNDERLYING
STRUCTURE
Firm attachment
to underlying
muscle
Loose attachment
to periosteum
Loose attachment
to underlying
muscle
Loose attachment
to underlying
tissues
Not distinct;
Attached to
underlying muscle

֎CHANGES IN LABIAL & BUCCAL MUCOSA
Trauma or any frictional force can lead to keratinization of non-keratinized
epithelium. Such a transformation in the buccal mucosa at the level of the
occlusal line because of the friction caused by the cusps of the occluding
teeth is called linea alba. Linea alba occurs as a white line which is readily
visible on clinical examination.
In case of patients with habits such as night grinding (bruxism), a larger area
of the buccal mucosa can demonstrate keratinization. The clinical
identification of such a modification can be a clue in terms of diagnosis of
parafunctional habits of the patient.
Occasionally, sebaceous glands may be present in the connective tissue of
cheeks presenting as yellow spots called Fordyce spots in the mucosa on
clinical examination. This presentation is a developmental anomaly rather
than a disease state.

֎SUBLINGUAL DRUG DELIVERY
The thin non-keratinized epithelium & larger veins underneath the ventral
surface of the tongue & floor of the mouth favour easy drug delivery.
The drug when placed underneath the tongue is absorbed swiftly by the
body.
An example of such a placement of drug is nitroglycerine tablets that relieve
angina.

The mucosa covering the dorsal surface of the tongue is different from that
seen anywhere else in the oral cavity.
It is mostly keratinized.
It has different types of papillae, some of which bear taste buds.
In addition to its mechanical function, the tongue has an important sensory
function (taste) & the mucosa covering the dorsal surface of the tongue is
regarded as specialized mucosa.
The dorsal surface of the tongue is divided into anterior two-third & posterior
one-third by a V-shaped groove, the sulcus terminalis.
While the mucosa covering the anterior two-third or the body of the tongue
has numerous papillae, the mucosa covering the posterior one-third or the
base of the tongue contains nodules of lymphoid tissue.
The papillae on the anterior two-third of the tongue are of four types.

1. Filiform papillae:
 They cover almost the entire anterior surface & give the tongue a velvety
appearance.
 These are cone-shaped structures consisting of a core of lamina propria
covered by keratinized stratified squamous epithelium forming hair-like tufts.
 This gives the tongue an abrasive surface & helps it to be involved in
mastication by compressing the bolus of food against palate.
 There are no taste buds in filiform papillae.

2. Fungiform papillae:
 They are isolated, elevated, mushroom-shaped papillae scattered between
numerous filiform papillae.
 They are reddish, round, smooth structures.
 The redness is due to the rich vascularity of lamina propria which is visible
through the thin overlying epithelium.
 Few taste buds are found on their superior surface.

3. Foliate papillae:
 They are leaf-like papillae seen on the lateral margin of the posterior part of
the tongue.
 They present as clefts/ grooves & show taste buds on their lateral walls.

4. Circumvallate papillae:
 They are about 10 in number, situated just in front of V-shaped sulcus
terminalis.
 These are large (2–4 mm), rounded & in level with the surface of the tongue.
 They are surrounded by a circular groove & a wall (vallum) & hence get their
name ‘circumvallate’.
 The ducts of the underlying serous glands— von Ebner’s glands—open into
these grooves surrounding the papilla.
 These papillae are covered by keratinized epithelium on their superior
surface.
 The epithelium covering their lateral wall (facing the groove) is non-
keratinized & has numerous taste buds.

FILIFORM
PAPILLAE
CIRCUMVALLATE
PAPILLAE
FUNGIFORM
PAPILLAE
FOLIATE
PAPILLAE

֎GEOGRAPHIC TONGUE
It is also called benign migratory glossitis & appears as red & white areas in
the tongue.
The redness corresponds to loss of filiform papillae & the white areas
correspond to Orthokeratinization of the filiform papillae.
This lesion might be associated with the burning sensation of the tongue.

֎BLACK HAIRY TONGUE
Epithelial turnover of filiform papillae is affected leading to accumulation of a
thick layer of keratin, debris & dead cells in the tongue causing black hairy
appearance.
Brushing the tongue is advised to remove the debris & dead cells.
Brushing also activates shedding of epithelial cells.

֎WHITE COATING ON THE TONGUE
Desquamated cells of the oral mucosa are present in saliva & they settle on
the dorsum of the tongue forming a white coating.
Patients should be advised to brush the dorsal surface of the tongue to avoid
white coating & subsequent microbial colonization which might lead to bad
breath.

SENSATION OF TASTE
The sense of taste is mediated by taste receptor cells present in the taste
buds.
The taste receptor cells within a bud are arranged such that their tips form a
small taste pore, & through this pore, microvilli extend from the taste cells.
The microvilli of the taste cells bear taste receptors.
Taste cells are stimulated by binding of chemicals to their receptors.
They depolarize, & this depolarization is transmitted to the taste nerve fibres
resulting in an action potential that is ultimately transmitted to the brain.
The sensitivity of taste buds to sweet, salty, sour, & bitter substances shows
regional variation (sweet at the tip, salty & sour on the lateral aspects, & bitter
& sour in the posterior region of the tongue).

FEATURES DORSAL SURFACE OF THE TONGUE
COVERING EPITHELIUM STRATIFIED SQUAMOUS EPITHELIUM
EPITHELIAL THICKNESS THICK
TYPE OF KERATINIZATION
KERATINIZED IN ANTERIOR TWO THIRD & NON-
KERATINIZED IN POSTERIOR ONE THIRD

FEATURES DORSAL SURFACE OF THE TONGUE
TYPES OF FIBRES PRESENT Collagen & some elastic fibers
STRUCTURE OF PAPILLA
In the anterior two third, long papilla & in the
posterior one third, short papillae
VASCLARITY
Capillary plexus in papillary layer, large vessels lie
deeper
ATTACHMENT
TO UNDERLYING
STRUCTURE
Not distinct; attached to underlying muscle

Within the oral mucosa there are three junctions:
1. The mucocutaneous (between the skin & mucosa)
2. The mucogingival (between the gingiva & alveolar mucosa)
3. The dentogingival (interface between the gingiva & the tooth)
The junction between the epithelium & the enamel is the principal seal
between the oral cavity & the underlying tissues, & hence represents a first
line of defense against periodontal disease.

1. MUCOCUTANEOUS JUNCTION
The skin, which contains hair follicles & sebaceous & sweat glands, is
continuous with the oral mucosa at the lips.
At the mucocutaneous junction is a transitional region where appendages are
absent except for a few sebaceous glands (situated mainly at the angles of
the mouth).
The epithelium of this region is keratinized but thin, with long connective
tissue papillae containing capillary loops.
This arrangement brings the blood close to the surface & accounts for the
strong red coloration in this region, called the red (or vermilion) zone of the
lip.
The line separating the vermilion zone from the hair-bearing skin of the lip is
called the vermilion border.

In young people this border is demarcated sharply, but as a person is
exposed to ultraviolet radiation, the border becomes diffuse & poorly defined.
Because the vermilion zone lacks salivary glands & contains only a few
sebaceous glands, it tends to dry out, often becoming cracked & sore in cold
weather.
Between the vermilion zone & the thicker, non-keratinized labial mucosa is
an intermediate zone covered by parakeratinized oral epithelium.
In infants this region is thickened & appears more opalescent, which
represents an adaptation to suckling called the suckling pad.

SAGITTAL SECTION THROUGH THE LIP
A: The skin covering the external aspect has a
thin epidermis & contains hair follicles.
Continuous with this is the vermilion zone, which
has a thin epithelium overlying an area of
extensive vascularity. Between the vermilion zone
& the labial mucosa of the oral cavity is the
intermediate zone. Minor salivary glands occur
beneath the labial mucosa, & the extensive
muscular tissue represents part of the orbicularis
oris.
B: Higher magnification of the area of vascularity
in the vermilion border showing multiple capillary
loops, in the connective tissue, close to the
surface.

2. MUCOGINGIVAL JUNCTION
This is the junction between attached gingiva & alveolar mucosa.
It is identified clinically by a slight indentation called the mucogingival groove
& by the change from the bright pink of the alveolar mucosa to the paler pink
of the gingiva.
Histologically, a change occurs in the type of epithelium & in the composition
of the lamina propria.
The epithelium of the attached gingiva is keratinized or parakeratinized, & the
lamina propria contains numerous coarse collagen bundles attaching the
tissue to periosteum.
The stippling seen clinically at the surface of healthy attached gingiva
probably reflects the presence of this collagen attachment, the surface of the
free gingiva being smooth.

The structure of mucosa changes at the mucogingival junction, where the
alveolar mucosa has a thicker, non-keratinized epithelium overlying a loose
lamina propria with numerous elastic fibers extending into the thick
submucosa.
These elastic fibers return the alveolar mucosa to its original position after
distention by the labial muscles during mastication & speech.
Coronal to the mucogingival junction is another clinically visible depression in
the gingiva, the free gingival groove, the level of which corresponds
approximately to that of the bottom of the gingival sulcus.
This demarcates the free & attached gingivae, although unlike the
mucogingival junction, no significant change in the structure of the mucosa
occurs at the free gingival groove.

SECTIONS THROUGH THE MUCOGINGIVAL JUNCTION (dashed line)

2. DENTOGINGIVAL JUNCTION
The region where the oral mucosa meets the surface of the tooth is a unique
junction of considerable importance because it represents a potential
weakness in the otherwise continuous epithelial lining of the oral cavity.
The dentogingival junction consists of a sulcular epithelium which extends
cervically to become the junctional epithelium that attaches to the tooth
surface.
When the tooth first becomes functional, the bottom of the sulcus usually is
found on the cervical half of the anatomic crown; with age a gradual migration
of the sulcus bottom occurs that eventually may pass on to the cementum
surface.

SECTIONS THROUGH THE DENTOGINGIVAL JUNCTION (dashed line)

CLINICAL CHANGES
Enlargement of lingual veins occur leading to lingual varicosities in the
ventral surface of the tongue sometimes called caviar tongue.
Slowly, depapillation of tongue might set in consequently leading to reduction
in taste buds. Subsequently, taste perception might also get diminished.
Many a times, such a change in the tongue happens because of medications
taken or an associated disease process in older individuals.
Medications may also lead to hypo salivation & consequent dryness of the
mouth.
Stippling in the attached gingiva is diminished.
Creasing in the labial commissures occurs due to loss of vertical dimension
subsequent to loss of tooth & resorption of jaws.
The repair & healing capability of oral mucosa is diminished.

HISTOLOGICAL CHANGES
The number & thickness of rete ridges reduce
Mitotic activity reduces
The degree of keratinization is diminished
Turnover time gets prolonged
Collagen bundles are thickened
The quality of elastic fibres is reduced leading to reduction in the resiliency of
oral mucosa
Collagen turnover time is prolonged
Fibroblasts appear smaller & the activity is diminished

Oral mucous membrane

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Oral mucous membrane

Similar to Oral mucous membrane (20)

More from ishita1994

More from ishita1994 (20)

Recently uploaded

Recently uploaded (20)

Oral mucous membrane