The oral epithelium acts as a protective barrier for the oral mucosa. It is composed of keratinocytes that undergo proliferation and maturation as they move from the basal layer to the surface. Keratinocytes express different cytokeratins as they mature and differentiate. The oral epithelium can be keratinized or non-keratinized depending on its location. A basement membrane anchors the epithelium. Various cellular disorders can affect the oral epithelium. Non-keratinocytes including melanocytes, Langerhans cells, and lymphocytes are also present in small numbers.

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