GOOD MORNING….

ORAL EPITHELIUM

DR NAVEEN PARVATHAREDDY I MDS, NARAYANA DENTAL COLLEGE

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

INTRODUCTIONTHE TISSUE THAT FORMS THE SURFACE OF THE ORAL

MUCOSA

ACTS AS A BARRIER

IT IS OF STRATIFIED SQUAMOUS TYPE

MAINTAIN STRUCTURAL INTEGRITY

DERIVED FROM

TYPES OF ORAL EPITHELIUM ORTHOKERATINISED PARAKERATINISED NON

KERATINISED

GINGIVAL EPITHELIUM• JUNCTIONAL

EPITHELIUM• SULCULAR

EPITHELIM

KERATINOCYTES

KERATINOCYTES CONSISTS OF 2 FUNCTIONAL

POPULATIONS

• PROGENITOR POPULATION – PERFORMING

EPITHELIAL PROLIFERATION

• MATURING POPULATION – PERFORMING

EPITHELIAL MATURATION

CYTOKERATINS IN ORAL EPITHELIUM

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

Based on distribution Soft keratin Hard keratin

Based on X-ray diffraction pattern Alpha Beta Feather keratins Amorphous keratins

Types of keratins

Based on amino acid sequence and chargeo Type I: Acidic proteins : Keratins 9-20 o Type II: Basic or neutral proteins : Keratins 1-8

Based on molecular weighto Low molecular weight keratins(40kDa)o Intermediate molecular weight keratinso High molecular weight keratins(67kDa)

Known as intermediate filament associated proteins These include

Filaggrin

Trichohyalin

Desmosomal proteins

Proteins of cornified cell envelope

Keratin associated proteins

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

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.

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

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)

They together makes up 10% of cell population in the

oral epithelium

In light microscope –

No tonofilaments

No maturation

NON – KERATINOCYTES

Different non- keratinocytes in oral epithelium are

Melanocytes

Langerhans cells

Merkel cells

Inflammatory cells

Melanocytes LM EM

Langerhans Cells

H & E EM

Merkel Cells

INFLAMMATORY CELLS

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-

Epithelial proliferation

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 daysCheek – 25 days

Proliferation is controlled by biologically active substances called cytokines

MATURATION

Maturation follows 2 main patterns

Keratinization

Non– keratinization

Keratinization Occurs in masticatory mucosa which is

tough & resistant to abrasion

Histologically , shows a number of distinct layers or strata

Stratum basale OtherwiseDeepest layerFormed byBasal cells show

Stratum spinosum Otherwise Situated Contacts only at points known as intercellular bridges or

desmosomesBasal and prickle cell constitutesStratum germinivatum

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

Stratum granulosm Next to spinous layer

Consists of large flattened cells

Cells contain small granules that stain immensely with

hematoxylin

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

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

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

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

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

Stratum superficialeThe cells of the superficial layer,

Are more flattened

Contain dispersed tonofilaments and nuclei

Number of cell organelles are diminished

Not dehydrated

CELLULAR EVENTS IN CELL MATURATION

• CELL SIZE• TONOFILAMENTS• KERATINS• GRANULAR LAMELLAE• PERMEABILITY BARRIER

Keratinised epithelia Non keratinized epithelia

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

Permeability & absorption

BASEMENT MEMBRANE

• 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

• MAIN CONSTITUENTS OF BM ARE

• THE GLYCOSAMINOGLYCAN, HEPARIN SULPHATE

• FIBROUS PROTEIN –COLLAGEN TYPE-IV , VII

• STRUCTURAL GLYCOPROTEINS – FIBRONECTIN , LAMININ & ENACTIN

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

EPITHELIAL DISORDERS:

Epithelial atrophy Epithelial hyperplasia

HYPERKERATOSIS ULCERATED EPITHELIUM

ACANTHOLYSISACANTHOSIS

SUMMARY

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

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

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

CYTOKERATINS EXPRESSION IN EPITHELIAL TUMOR CELLS:

•best IHC marker for Merkel‑cell carcinomasCk 20

•markers for poorly differentiated squamous cell carcinomaCk 13 •a marker for odontogenic epithelial origin

Ck 14 & 19

Keratins can be used as differentiation markers in normal oral epithelia:

K8/18• markers for simple epithelial differentiation

K1/10• markers for keratinized epithelium

K4/13• markers for non-keratinized epithelium.

K6/16• considered as hyperproliferative markers• expressed in sites of high epidermal keratinocyte turnover and in pathological hyperproliferative conditions affecting the skin

SPECIAL STAINS

• MELANOCYTES- • LANGERHANS CELLS-• MERKEL CELLS-• LYMPHOCYTES-

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

REFERENCES