oral epithelium , dr naveen reddy
TRANSCRIPT
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GOOD MORNING….
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ORAL EPITHELIUM
DR NAVEEN PARVATHAREDDY I MDS, NARAYANA DENTAL COLLEGE
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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
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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
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TYPES OF ORAL EPITHELIUM ORTHOKERATINISED PARAKERATINISED NON
KERATINISED
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GINGIVAL EPITHELIUM• JUNCTIONAL
EPITHELIUM• SULCULAR
EPITHELIM
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KERATINOCYTES
KERATINOCYTES CONSISTS OF 2 FUNCTIONAL
POPULATIONS
• PROGENITOR POPULATION – PERFORMING
EPITHELIAL PROLIFERATION
• MATURING POPULATION – PERFORMING
EPITHELIAL MATURATION
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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
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Based on distribution Soft keratin Hard keratin
Based on X-ray diffraction pattern Alpha Beta Feather keratins Amorphous keratins
Types of keratins
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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)
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Known as intermediate filament associated proteins These include
Filaggrin
Trichohyalin
Desmosomal proteins
Proteins of cornified cell envelope
Keratin associated proteins
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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
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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.
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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
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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)
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They together makes up 10% of cell population in the
oral epithelium
In light microscope –
No tonofilaments
No maturation
NON – KERATINOCYTES
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Different non- keratinocytes in oral epithelium are
Melanocytes
Langerhans cells
Merkel cells
Inflammatory cells
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Melanocytes LM EM
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Langerhans Cells
H & E EM
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Merkel Cells
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INFLAMMATORY CELLS
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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
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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
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Proliferation is controlled by biologically active substances called cytokines
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MATURATION
Maturation follows 2 main patterns
Keratinization
Non– keratinization
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Keratinization Occurs in masticatory mucosa which is
tough & resistant to abrasion
Histologically , shows a number of distinct layers or strata
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Stratum basale OtherwiseDeepest layerFormed byBasal cells show
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Stratum spinosum Otherwise Situated Contacts only at points known as intercellular bridges or
desmosomesBasal and prickle cell constitutesStratum germinivatum
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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
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Stratum granulosm Next to spinous layer
Consists of large flattened cells
Cells contain small granules that stain immensely with
hematoxylin
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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
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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
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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
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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
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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
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Stratum superficialeThe cells of the superficial layer,
Are more flattened
Contain dispersed tonofilaments and nuclei
Number of cell organelles are diminished
Not dehydrated
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CELLULAR EVENTS IN CELL MATURATION
• CELL SIZE• TONOFILAMENTS• KERATINS• GRANULAR LAMELLAE• PERMEABILITY BARRIER
Keratinised epithelia Non keratinized epithelia
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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
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BASEMENT MEMBRANE
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• 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
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• MAIN CONSTITUENTS OF BM ARE
• THE GLYCOSAMINOGLYCAN, HEPARIN SULPHATE
• FIBROUS PROTEIN –COLLAGEN TYPE-IV , VII
• STRUCTURAL GLYCOPROTEINS – FIBRONECTIN , LAMININ & ENACTIN
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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
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EPITHELIAL DISORDERS:
Epithelial atrophy Epithelial hyperplasia
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HYPERKERATOSIS ULCERATED EPITHELIUM
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ACANTHOLYSISACANTHOSIS
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SUMMARY
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ORAL EPITHELIUM• SERRATED AND NON-SERRATED BASAL CELLS• CYTOKERATINS EXPRESSION• SPECIAL STAINS FOR NON-KERATINOCYTES
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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
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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
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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
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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
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SPECIAL STAINS
• MELANOCYTES- • LANGERHANS CELLS-• MERKEL CELLS-• LYMPHOCYTES-
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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
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