ultrastructure of gingiva

1. ULTRASTRUCTURE
OF
GINGIVA

2. GINGIVA
 It is that part of
oral mucosa that
covers the
alveolar
processes of jaw
and surrounds
the necks of
teeth

3. Clinically,
Gingiva is divided
clinically into:
 Marginal gingiva
 Attached gingiva
 Interdental
gingiva
 Gingival sulcus

4. Ultrastructurally,
Gingiva is composed
of
 Overlying
stratified
squamous
epithelium
 Central connective
tissue core

5. THE EPITHELIUM
 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
lumen

6. 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
manner.
 Signaling functions

7. 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.

8. 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
layers.

9. EPITHELIAL PROLIFERATION
 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
ridges
 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
maturation.

10.  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
mitosis.
 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.

11. ULTRASTRUCTURE OF
EPITHELIAL CELL
 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
tonofilaments
 Intercellular bridges or desmosomes.

12.  TONOFILAMENTS- are fibrous proteins
synthesized by the ribosomes and are seen as long
filaments.
 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
charge.
 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”

13.  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
14
 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.

14. EPITHELIAL MATURATION
 The cells arising by division in basal layer
undergo a maturation process as they move
to surface.
 Maturation follows two patterns:
(i) Keratinized
(ii) Non- keratinized

15. KERATINIZATION
 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
subsequently
 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

16.  type appearance
 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.

18. This process of keratinization forms two
patterns.
(i)orthokeratinization (ii)parakeratinization
ORTHOKERATINIZED
Uppermost layer do not
contain any nuclei
Stratum granulosum
has more no of
keratohyaline
granules
PARAKERATINIZED
Uppermost layer contains
pyknotic nuclei
The keratohyaline granules
are less in number and
dispersed

19. NON- KERATINIZED
 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
arbitrary zones
STRATUM INTERMEDIUM
STRATUM SUPERFICIALE
 Granular layer is absent
 Superficial layer consists of nuclei.
 This pattern leads to formation of flexible, soft
epithelium

20. NON-KERATINIZED EPITHELIUM

21.  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
cells themselves.
 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
(ii) hemidesmosomes
3. Communicating (gap) junctions

23.  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
intercellular spaces

24. ADHESIVE JUNCTIONS- Intercellular space is 20 nm
ZONULA ADHERENS
Junction that completely
encircles cells
Transmembrane proteins are
E-cadherin and catenin of
cadherin family
MACULA ADHERENS
Junction that is
circumscribed (spot like)
Transmembrane proteins are
desmoglein and desmocollin
of cadherin family

25. 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.

26. NON-KERATINOCYTES IN ORAL
EPITHELIUM
 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-
KERATINOCYTES.
 These cells make 10% of total cell population.
These cells are
 MELANOCYTES
 LANGERHANS’ CELLS
 MERKEL CELLS
 INFLAMMATORY CELLS

27.  MELANOCYTES- These cells arise embryologically from
neural crest ectoderm.
 Present in basal layer and produce melanin, the color
pigment.
 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.

28.  LANGERHANS’ CELLS- present in
suprabasal layers
 Dendritic in nature
 No desmosomes or tonofilaments.
 Antigenic in nature.
 Contain small rod or flask shaped granules
called as birbeck’s granules.

29.  MERKEL CELLS- present in basal layer.
 No desmosomes and tonofilaments.
 Unlike the other two cells, it is not dendritic in
nature.
 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

30.  INFLAMMATORY CELLS-seen transiently
in between nucleated cell layers.
 Most commonly seen are lymphocytes.
 Others are neutrophils and mast cells.
LYMPHOCYTE NEUTROPHIL MAST CELL

31. JUNCTION OF EPITHELIUM AND
CONNECTIVE TISSUE
 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.

32. HEMIDESMOSOMES FOCAL ADHESIONS

33.  Basal lamina act as filter to contro passage of
molecules.
 It also has signaling functions essential for
epithelial differentiation
 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

35. LAMINA PROPRIA
 The connective tissue supporting the oral
epithelium is termed as LAMINA PROPRIA.
 Divided in two layers:
PAPILLARY LAYER
RETICULAR LAYER
 Lamina propria consists of cells , blood vessels
neural elements and fibres embedded in
amorphous ground substance.
 Shows regional variation.

37. 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
plane.

38. CELLS OF CONNECTIVE TISSUE
The lamina propria contains several different cells
like fibroblasts , macrophages, mast cells and
inflammatory cells.
FIBROBLAST
 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
fibres
 Is an active synthetic cell that contains numerous
mitochondria, extensive granular endoplasmic
reticulum, prominent golgi complex and numerous

39. membrane bound vesicles.
 Have a low rate of proliferation except in
healing phases.
MACROPHAGES
 It is also a stellate shaped cell so difficult to
distinguish from fibroblast
 Smaller and denser nuclei and less granular

40. endoplasmic reticulum
 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
immunologic response.

41.  MAST CELL
 Large spherical or elliptical mononuclear
cell
 These cells are present in relation to blood
vessels so they play a role in maintaining
normal tissue stability and vascular
homeostasis.
 INFLAMMATORY CELLS
 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.

42. FIBRES AND GROUND SUBSTANCE
The intercellular matrix of lamina propria consists
of two major types of fibres
 COLLAGEN
 ELASTIC FIBRES
COLLAGEN
 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
collagens

43. 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.

44.  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.

45.  2. FIBRIL ASSOCIATED COLLAGENS (type IX,
XII,XIV)
 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.

46.  They are believed to impart compressive strength
while providing open porous network.
 ANCHORING FIBRIL COLLAGEN (type VII)
 It extend from basal lamina to underlying
connective tissue.
 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
XVII)
 Help in cell- matrix adhesion

47.  ELASTIN FIBRES
 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
required.
 In absence of elastin they are called as oxytalan fibres
 Developing elastic fibres are called as elaunin fibres

48. GROUND SUBSTANCE
 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
molecules
 Fibroblasts synthesize two main classes of
macromolecules making up ground substance –
proteoglycans and glycoproteins

49.  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
molecules.
GLYCOPROTEINS
 Major are fibronectin, tenascin,thrombospondin
 They are majorly involved in attachment spreading
and migration of cells and organization of collagen
fibrils.
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
factor etc.
 These have important roles in developmental
processes, wound healing and tissue remodelling.

50. GROUND SUBSTANCE

51. MICROCIRCULATION OF GINGIVA
Microcirculatory tracts, blood vessels and
lymphatic vessels play an important role in
drainage of tissue fluid and in spread of
inflammation.
Microcirculation can be evidenced by:
 Immunhistochemical reactions
 Histoenzymatic reactions
 Perfusion of dyes
 Scanning electron microscopy
 Laser doppler flowmetry

52.  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
sulcus area.
 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.

54.  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