ORAL EPITHELIUM

1. GOOD MORNING….

2. ORAL EPITHELIUM
DR NAVEEN PARVATHAREDDY
I MDS, NARAYANA DENTAL COLLEGE

3. CONTENTS
• INTRODUCTION
• TYPES OF ORAL EPITHELIUM
• KERATINOCYTES
CYTOKERATINS IN ORAL EPITHELIUM
KERATIN ASSOCIATED PROTEINS
• NON-KERATINOCYTES
• EPITHELIAL PROLIFERATION
• EPITHELIAL MATURATION
• CELLULAR EVENTS IN CELL MATURATION
• BASEMENT MEMBRANE
• EPITHELIAL DISORDERS
• SUMMARY
• REFERENCES

4. INTRODUCTION
THE TISSUE THAT FORMS THE SURFACE OF THE ORAL MUCOSA
ACTS AS A BARRIER
IT IS OF STRATIFIED SQUAMOUS TYPE
MAINTAIN STRUCTURAL INTEGRITY
DERIVED FROM

5. TYPES OF ORAL EPITHELIUM
ORTHOKERATINISED PARAKERATINISED NON KERATINISED

6. GINGIVAL EPITHELIUM
• JUNCTIONAL EPITHELIUM
• SULCULAR EPITHELIM

7. KERATINOCYTES
KERATINOCYTES CONSISTS OF 2 FUNCTIONAL POPULATIONS
• PROGENITOR POPULATION – PERFORMING
EPITHELIAL PROLIFERATION
• MATURING POPULATION – PERFORMING EPITHELIAL
MATURATION

8.  Keratins (previously also called cytokeratins) are
filament forming proteins of epithelial cells and are
essential for normal tissue structure and function
 Forms the cytoskeleton of all the epithelial cells,
along with microfilaments & microtubules.
 Provide mechanical linkage & distribute force over
wide area

9. Based on distribution
Soft keratin
Hard keratin
Based on X-ray diffraction pattern
Alpha
Beta
Feather keratins
Amorphous keratins

10. Based on amino acid sequence and charge
o Type I: Acidic proteins
: Keratins 9-20
o Type II: Basic or neutral proteins
: Keratins 1-8
Based on molecular weight
o Low molecular weight keratins(40kDa)
o Intermediate molecular weight keratins
o High molecular weight keratins(67kDa)

11.  Known as intermediate filament associated proteins
 These include
Filaggrin
Trichohyalin
Desmosomal proteins
Proteins of cornified cell envelope

12. FILAGGRIN
• CATIONIC PROTEIN; AIDS IN
DENSE PACKING OF KERATIN
• SYNTHESIZED IN THE
GRANULAR CELL LAYER
• FACILITATES DISULFIDE BOND
FORMATION
• MARKER FOR KERATINIZED
TYPE OF EPITHELIUM

13. TRICHOHYALIN
• EXPRESSED IN THE KERATINIZING FILIFORM PAPILLA OF
TONGUE
• SINGLE STRANDED ALPHA-HELICAL ROD THAT BIND
KERATIN
• FUNCTION AS INTRACELLULAR CEMENT
• ALSO FUNCTIONS AS CROSS BRIDGING PROTEINS.

14. DESMOSOMAL PROTEINS
• LINKS EPITHELIAL CELLS TO EACH OTHER; ATTACHES KERATIN
CYTOSKELETON TO CELL SURFACE
• INTEGRAL PROTEINS: DESMOGLEIN & DESMOCOLLIN
• CYTOPLASMIC PLAQUE PROTEIN: DESMOPLAKIN & PLAKOGLOBIN
• PLAQUE ASSOCIATED PROTEINS: PLAKOPHILIN, ENVOPLAKIN &
PERIPLAKIN

15. PROTEINS OF CORNIFIED CELL ENVELOPE
• DEPOSITED ON THE INNER FACE OF PLASMA MEMBRANE OF
KERATINOCYTES.
• BARRIER FUNCTION OF STRATIFIED KERATINIZED EPITHELIA
• EXPRESSED IN
• MOST ABUNDANT CE PROTEINS
oLORICRIN
oINVOLUCRIN
oSMALL PROLINE RICH PROTEINS (SPR’S)

16.  They together makes up 10% of cell population in
the oral epithelium
 In light microscope –
 No tonofilaments
 No maturation

17.  Different non- keratinocytes in oral epithelium are
Melanocytes
Langerhans cells
Merkel cells
Inflammatory cells

18. Melanocytes
LM EM

19. Langerhans Cells
H & E EM

20. Merkel Cells

21. INFLAMMATORY CELLS

22.  Progenitor cells present in the basal layer
 Dividing cells tend to occur on clusters
 Progenitor compartment consists of 2 functional sub
population of cells
◦ Small stem cells-
◦ Large amplifying cells-

25.  Turnover time of the epithelium is the time it takes
for a cell to divide and pass through the entire
epithelium
 Turnover time
Skin – 52 – 75 days
Gut – 4 – 14 days
Gingiva – 41 – 57 days
Cheek – 25 days

26.  Proliferation is controlled by biologically active
substances called cytokines

27. MATURATION
Maturation follows 2 main patterns
Keratinization
Non– keratinization

28. Keratinization
Occurs in masticatory mucosa which is tough
& resistant to abrasion
Histologically , shows a number of distinct
layers or strata

30. Stratum basale
Otherwise
Deepest layer
Formed by
Basal cells show

31. Stratum spinosum
 Otherwise
 Situated
 Contacts only at points known as intercellular bridges or desmosomes
 Basal and prickle cell constitutes
 Stratum germinivatum

32. LAMELLAR BODIES, LAMELLAR GRANULES,
MEMBRANE COATING GRANULES OR
KERATINOSOMES.
THESE GRANULES ARE
• SMALL
• MEMBRANE BOUND
• SIZE – 250 NM
• CONTAIN GLYCOLIPID
• ORIGINATE FROM GOLGI SYSTEM
ODLAND BODIES

33. Stratum granulosm
Next to spinous layer
Consists of large flattened cells
Cells contain small granules that stain immensely with
hematoxylin

34. KERATOHYALIN GRANULES
• CHARACTERISTIC FEATURE
• UNDER LM,EM
• IRREGULAR IN SHAPE
• SIZE 0.5 – 1 MICROMETER
• SYNTHESIZED BY RIBOSOMES
• KERATOHYALIN GRANULES ASSOCIATED WITH
TONOFIBRILS ,
• FILAGGRIN, LORICRIN

35. Stratum corneaum
Surface layer
Composed of very flat cells
Eosinophilic, do not contain any nuclei
This pattern of maturation is called orthokeratinization
Some times in some mucosa, retain the shrunken nuclei
called as parakeratinisation

36. Non keratinization
◦ Usually the lining mucosa
◦ Basal & prickle layers resemble that of keratinized
except the prickle cells of non- keratinized epithelium
are slightly larger and intercellular bridges are less
conspisious

37. Above the prickle layer, divided into 2 zones
Stratum intermedium
Stratum superficiale
# No granular layer
# Superficial layer contain plump nucleus
# Not stain intensely with eosin

38. spinous cell layer (s. intermedium)
In prickle cell layer, increase in size is more than that of
keratinized epithelium
Tonofilaments remain dispersed
Contain membrane bound granules
They are circular in shape, with an amorphous coat

39. Stratum superficiale
The cells of the superficial layer,
Are more flattened
Contain dispersed tonofilaments and nuclei
Number of cell organelles are diminished
Not dehydrated

40. • CELL SIZE
• TONOFILAMENTS
• KERATINS
• GRANULAR LAMELLAE
• PERMEABILITY BARRIER
Keratinised epithelia Non keratinized epithelia

41.  Depends on the
Thickness of the epithelium
Pattern of maturation
Thinnest epithelium allow better penetration
Permeability barrier is due to the lipids derived
from the membrane coating granules

42. BASEMENT MEMBRANE

43. • FORMED BY
• LM – AMORPHOUS, DENSE LAYER OF VARIABLE THICKNESS
• PAS STAIN - WELL DEFINED MAGENTA LAYER
• IN ELECTRON MICROSCOPE BM CONSISTS OF 3 LAYER
• LAMINA LUCIDA
• LAMINA DENSA
• LAMINA FIBRO-RETICULARIS
BASEMENT MEMBRANE

44. • MAIN CONSTITUENTS OF BM ARE
• THE GLYCOSAMINOGLYCAN, HEPARIN SULPHATE
• FIBROUS PROTEIN –COLLAGEN TYPE-IV , VII
• STRUCTURAL GLYCOPROTEINS – FIBRONECTIN , LAMININ &
ENACTIN

45. Functional role
 Compartmentalize tissues
 Anchor cell sheets
 Play major role in control of cell migration
 Act as an stimulus
 Serve as a barrier
 As epithelium devoid of blood vessels
 Fenestrations in BM

46. EPITHELIAL DISORDERS:
Epithelial atrophy Epithelial hyperplasia

48. HYPERKERATOSIS ULCERATED EPITHELIUM

49. ACANTHOLYSISACANTHOSIS

51. ORAL EPITHELIUM
• SERRATED AND NON-SERRATED BASAL CELLS
• CYTOKERATINS EXPRESSION
• SPECIAL STAINS FOR NON-KERATINOCYTES

53. SERRATED HEAVILY PACKED WITH TONOFILAMENTS WHICH
ARE ADAPTATIONS FOR ATTATCHMENT
NON-SERRATED - SLOWLY DIVIDING CELLS WHICH SERVE TO
PROTECT GENETIC INFORMATION OF TISSUE
• PERIMETER OF BOTH NUCLEUS & CYTOPLASM
• CYTOPLASM IS PRIMITIVE & CONTAIN

54. Cytokeratin expression in normal oral
mucosa:
Basal cells
• Keratinised sites : k5 & k14
• Non-keratinised sites : k19
Supra-basal cells
• Keratinised sites : k1 & k10
• Non-keratinised sites : k4 & k13

55. CYTOKERATINS EXPRESSION IN EPITHELIAL
TUMOR CELLS:
• best IHC marker for Merkel-cell
carcinomas
Ck 20
• markers for poorly differentiated
squamous cell carcinoma
Ck 13
• a marker for odontogenic epithelial
origin
Ck 14 & 19

56. Keratins can be used as differentiation markers in
normal oral epithelia:
• markers for simple epithelial differentiation
K8/18
• markers for keratinized epithelium
K1/10
• markers for non-keratinized epithelium.
K4/13
• considered as hyperproliferative markers
• expressed in sites of high epidermal keratinocyte turnover and in pathological
hyperproliferative conditions affecting the skin
K6/16

57. • MELANOCYTES-
• LANGERHANS CELLS-
• MERKEL CELLS-
• LYMPHOCYTES-

58.  Ten Cates Oral Histology – Antonio Nanci –
8th edition
 Anatomy, histology & embryology –
Berkovitz – 3rd edition
 Atlas of histology – Difiore’s – 9th edition
 Text book of basic histology – Wheater’s
 Text book of human histology – Inderbir
Singh – 5th edition
 Ham’s histology -9th edition
 Internet sources