Gingiva is composed
Gingival epithelium is composed of
stratified squamous epithelium( flat scale
like cells with lumen and arranged in layers)
It consists of constantly renewing cell
population in which cell produced are just
sufficient to match those lost by
desquamation at the surface
FUNCTIONS OF EPITHELIUM
Protective covering for the tissues
beneath and a barrier to entry of foreign
material and micro-organisms.
Active role in innate host defense by
responding to bacteria in interactive
PARTS OF EPITHELIUM
Functionally and morphologically epithelium
is divided into:
Oral epithelium- which faces oral cavity
Oral sulcular epithelium- which faces tooth
without being in contact with it
Junctional epithelium- which provides
contact between gingiva and tooth.
ULTRASTRUCTURE OF EPITHELIUM
The epithelium covering gingiva is
stratified squamous i.e. the cells are
arranged in layers in which the cells arising
in the basal region undergo a process of
differentiation to form a protective
surface layer. The surface layers may have
different patterns but similar pattern of
differentiation can be recognized in basal
The progenitor cells are situated in basal layer.
Dividing cells tend to occur in clusters that are
seen more frequently at the bottom of epithelial
These clusters of cells contain two types of cells
(i) small population of stem cells which retain
proliferative potential of tissue.
(ii) larger population of amplifying cells which
increase number of cells available for subsequent
The control of cell division is
thought to be brought by
locally produced tissue
hormones called as
CHALONES. These are
produced by post-mitotic
epithelial cells and have dual
property of stimulating cell
differentiation and inhibiting
Various cytokines affect cell
division and proliferation like
epidermal growth factor,
keratinocyte growth factor,
IL-1, TGF-α and β
Other factors affecting cell
division are adrenaline, stress,
age, diurnal rhythm.
Turnover time of epithelium
varies from 5- 57 days.
Cells of basal layer are least
differentiated oral epithelial cells. They
contain not only organelles like
mitochondria, ribosomes, endoplasmic
reticulum and golgi complexes but also
contains certain characteristic structures
that identify them as epithelial cells and
distinguish them from other cell types.
These structures are:
Filamentous structures called as
Intercellular bridges or desmosomes.
TONOFILAMENTS- are fibrous proteins
synthesized by the ribosomes and are seen as long
Diameter is approximately 8nm.
Chemically, they are a class of intracellular proteins
known as cytokeratins which are characteristically
present in epithelial tissues.
These are classified according to their size and
These become aggregated to form bundles of filaments
called as tonofibrils.
Due to presence of these keratin filaments epithelial
cells are also called as “ keratinocytes”
Keratins represent 30 different proteins of
differing molecular weights.
Those with the lowest molecular weight (40 kDa)
are found in glandular and simple epithelia.
Those with intermediate molecular weight are
present in stratified epithelia.
Those with highest molecular weight( 67 kDa) in
keratinized stratified epithelium.
All stratified oral epithelia possess keratins 5 and
Keratinized oral epithelium contains 1, 6 ,10 and 16
Non keratinized epithelium 4, 13 and 19
Other proteins unrelated to keratins synthesized
in cell are KERATOLININ AND INVOLUCRIN.
They are precursors of chemically resistant
structures located below cell membrane and
FILAGGRIN which form matrix of corneocyte.
The cells arising by division in basal layer
undergo a maturation process as they move
Maturation follows two patterns:
(ii) Non- keratinized
This process leads to formation of epithelium
which is inflexible, tough, resistant to abrasion
and tightly bound to underlying connective tissue.
LAYERS OF KERATINIZED EPITHELIUM
STRATUM BASALE- the basal layer in this
pattern is composed of cuboidal or columnar cells
adjacent to basement membrane. This layers
consists of cells which divide and proliferate
STRATUM SPINOSUM- this layer consists of
larger elliptical or spherical cells which shrink
away from each other remaining in contact at
certain points only giving it a spike or prickle
So, also called as “prickle cell” layer
Upper layer contains dense granule
“keratinosomes or Odland bodies”. They
are modified lysosomes
STRATUM GRANULOSUM- it consists of
larger flattened cells .
The cells typically consist of granules
called as “keratohyaline granules”
STRATUM CORNEUM- it is the surface
layer composed of flat (squamous) cells.
The uppermost layer is cornified or horny.
This process of keratinization forms two
Uppermost layer do not
contain any nuclei
has more no of
Uppermost layer contains
The keratohyaline granules
are less in number and
Basal and prickle cell layers are same
No sudden changes in cell morphology is observed
above stratum spinosum.
The outer half of tissue is divided into two
Granular layer is absent
Superficial layer consists of nuclei.
This pattern leads to formation of flexible, soft
Important property of any epithelium is its ability
to function as a barrier which depends on close
contact or cohesiveness of epithelial cells.
Cohesion between cells is provided by a viscous
intracellular material consisting of protein-
carbohydrate complexes produced by epithelial
In addition, modifications of adjacent cell
membranes of cells occur. Main are
1. Occluding junctions (zonula occludens)
2. Adhesive junctions
(a) cell to cell
(i) zonula adherens
(ii) macula adherens(desmosomes)
(b) cell to matrix
(i) focal adhesions
3. Communicating (gap) junctions
TIGHT JUNCTIONS- the opposing cell
membranes are held in close contact by the
presence of transmembrane adhesive proteins
(occludin, claudin ) arranged in anastomosing
strands that encircle the cell.
They control the passage of material through
ADHESIVE JUNCTIONS- Intercellular space is 20 nm
Junction that completely
Transmembrane proteins are
E-cadherin and catenin of
Junction that is
circumscribed (spot like)
Transmembrane proteins are
desmoglein and desmocollin
of cadherin family
COMMUNICATING OR GAP JUNCTIONS
These are plaque like regions of cell membrane where
intercellular space narrows to 2-3 nm.
Transmembrane proteins are of connexin family
These junctions have electrically coupled cells and
allow for coordinated response to a stimulus by cells
that are interconnected.
NON-KERATINOCYTES IN ORAL
Apart from keratinocytes oral epithelium contains
cells that differ in appearance from other
keratinocytes in having a clear halo around their
nuclei so, are termed as CLEAR CELLS or NON-
These cells make 10% of total cell population.
These cells are
MELANOCYTES- These cells arise embryologically from
neural crest ectoderm.
Present in basal layer and produce melanin, the color
Melanin is produced in melanosomes and then inoculated
into cytoplasm of adjacent keratinocytes
These cells lack desmosomes and tonofilaments but have
long dendritic process extending between keratinocytes.
LANGERHANS’ CELLS- present in
Dendritic in nature
No desmosomes or tonofilaments.
Antigenic in nature.
Contain small rod or flask shaped granules
called as birbeck’s granules.
MERKEL CELLS- present in basal layer.
No desmosomes and tonofilaments.
Unlike the other two cells, it is not dendritic in
Contains small granules which may liberate
transmitter substance across the synapse- like
junction between cell and nerve fibre thus
triggering an impulse.
So they are supposed to be sensory and they
respond to touch
INFLAMMATORY CELLS-seen transiently
in between nucleated cell layers.
Most commonly seen are lymphocytes.
Others are neutrophils and mast cells.
LYMPHOCYTE NEUTROPHIL MAST CELL
JUNCTION OF EPITHELIUM AND
The region where the epithelium and underlying
connective tissue meet appears as an undulating
interface at which papillae of connective tissue
interdigitate with epithelial ridges
Ultrastructurally, this region is called as basal
lamina and is highly organized.
This structure along with hemidesmosomes
attaches epithelium to C.T. Also there are some
focal adhesions presnt.
Basal lamina act as filter to contro passage of
It also has signaling functions essential for
It has an overall thickness of 50 to 100 nm.
Has two structural components called as lamina
lucida adjacent to epithelium and lamina densa
adjacent to connective tissue.
Main constituent is type IV collagen , adhesive
glycoprotein laminin and fibronectin.
Also contains type III ( reticular fibres ) and type
VII ( anchoring fibrils ) collagen
The connective tissue supporting the oral
epithelium is termed as LAMINA PROPRIA.
Divided in two layers:
Lamina propria consists of cells , blood vessels
neural elements and fibres embedded in
amorphous ground substance.
Shows regional variation.
PAPILLARY LAYER RETICULAR LAYER
-It is the superficial layer - It is the deeper layer
-Collagen fibres are thin - Fibres are arranged in
and loosely arranged. thick bundles and tend
to lie parallel tosurface
CELLS OF CONNECTIVE TISSUE
The lamina propria contains several different cells
like fibroblasts , macrophages, mast cells and
It is the principle cell present.
Is responsible for elaboration and turnover of
fiber and ground substance thus playing a key role
in maintaining tissue integrity.
It is fusiform or stellate shaped cell with a long
process that lie parallel to bundles of collagen
Is an active synthetic cell that contains numerous
mitochondria, extensive granular endoplasmic
reticulum, prominent golgi complex and numerous
membrane bound vesicles.
Have a low rate of proliferation except in
It is also a stellate shaped cell so difficult to
distinguish from fibroblast
Smaller and denser nuclei and less granular
Cytoplasm contains membrane bound vesicles
that can be identified as lysosomes.
Principal function is phagocytosis which is
important as it increases the antigenicity
before it is presented to lymphocytes for
Large spherical or elliptical mononuclear
These cells are present in relation to blood
vessels so they play a role in maintaining
normal tissue stability and vascular
Lymphocytes and plasma cells can be seen
scattered throughout the lamina propria in
small numbers normally
Their number increase during injury and
according to nature of injury.
FIBRES AND GROUND SUBSTANCE
The intercellular matrix of lamina propria consists
of two major types of fibres
It constitutes the most abundant proteins found
in the body
The collagen family consists of atleast 30
different genes, which produce 19 known types of
STRUCTURE OF COLLAGEN
All collagens are composed of three polypeptide
alpha chains coiled around each other to form
typical collagen triple-helix configuration.
Common features include amino acid GLYCINE in
every third position, high proline residues and
presence of hydroxylysine and hydroxyproline.
Are classified according to structure as
1. Fibrillar collagens( TYPES I, II , III, V and XI)
These are fibrils forming collagens
They show typical 64 nm banding pattern
Type I collagen is most abundantly found collagen.
Type II is found in cartilage
Type III is found in granulation tissue.
Type V is found associated with type I and III and type
XI is found associated with type II.
2. FIBRIL ASSOCIATED COLLAGENS (type IX,
These are collagens with interrupted triple helices
i.e. consist of chains that have different lengths
and contain a variety of non-collagenous domains.
IX is associated with type II and the other two
with type I.
These collagens are believed to modulate
interactions between adjacent fibrils.
3.MESHWORK FORMING COLLAGENS (TYPE
VIII and X)
Type VIII is associated with basal laminae
Type X is found in epiphyseal growth plate.
They are believed to impart compressive strength
while providing open porous network.
ANCHORING FIBRIL COLLAGEN (type VII)
It extend from basal lamina to underlying
MICROFIBRIL FORMING COLLAGEN (TYPE VI)
This collagen binds cells, proteoglycans and type I
collagen and act as a bridge between them.
TRANSMEMBRANE COLLAGEN (TYPE XIII and
Help in cell- matrix adhesion
These are rubber like protein produced by fibroblasts
and smooth muscle cells.
The elastic properties are due to numeous
intermolecular cross- links between lysine groups,
formed by enzymes lysyl oxidase .
Glycoproteins fibrillin 1 and 2 and microfibrils are
In absence of elastin they are called as oxytalan fibres
Developing elastic fibres are called as elaunin fibres
Ground substance of extracellular matrix consists
of complex mixture of macromolecules.
These macromolecules interact with cells and the
fibrous components of the matrix and are involved
in adhesion and signaling events.
The ground substance is highly hydrated which
helps in regulating tissue water content and
diffusion of nutrients, waste products and other
Fibroblasts synthesize two main classes of
macromolecules making up ground substance –
proteoglycans and glycoproteins
Proteoglycans are large group of cell surface
associated molecules that consists of protein core
to which glycosaminoglycan chains are attached
Their important property is to bind growth
factors, cytokines and other biologically active
Major are fibronectin, tenascin,thrombospondin
They are majorly involved in attachment spreading
and migration of cells and organization of collagen
GROWTH FACTORS AND CYTOKINES
Fibroblasts secrete number of growth factors,
cytokines and inflammatory mediators like IL-1,
IL-6, IL-8, TNF-α, PDGF, keratinocyte growth
These have important roles in developmental
processes, wound healing and tissue remodelling.
MICROCIRCULATION OF GINGIVA
Microcirculatory tracts, blood vessels and
lymphatic vessels play an important role in
drainage of tissue fluid and in spread of
Microcirculation can be evidenced by:
Perfusion of dyes
Scanning electron microscopy
Laser doppler flowmetry
Sources of blood supply
SUPRAPERIOSTEAL ARTERIOLES- along facial
and lingual surfaces of alveolar bone, from which
capillaries extend along the sulcular epithelium and
between rete pegs of external gingival surface.
VESSELS OF PERIODONTAL LIGAMENT- extend
into gingiva and anastomose with capillaries in
ARTERIOLES- emerge from crest of interdental
septa and extend parallel to crest of bone, then
forming anastomosis with other capillaries.
Beneath the epithelium the capillaries extend in
papillary connective tissue in the form of terminal
hair pin loops.
LYMPHATIC drainage of gingiva brings in the
lymphatics of connective tissue papillae .it
progresses into the collecting network external to
the periosteum of alveolar processes , then to
regional lymph nodes , particularly submaxillary
lymph node group
Lymphatics beneath the junctional epithelium
extend into the periodontal ligament and
accompany the blood vessels
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