HISTOLOGY OF ORAL MUCOSA AND GINGIVA AND PALATE

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HISTOLOGY OF ORAL MUCOSA AND GINGIVA AND PALATE
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THE MUCOGINGIVAL JUNCTION DELINEATES THE ORAL
MUCOSA WHICH IS VASCULAR ,HAS LOOSE COLLAGEN AND
ELASTIC FIBERS AND MUSCLE .IT IS COVERED BY A
THIN LAYER OF NON KERATINISED EPITHELIUM.THIS
PERMITS THE MOVEMENT AND STRETCHING ASSOCIATED
WITH MASTICATION ,SPEECH AND FACIAL EXPRESSION.
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UPPER MOLAR ON THE LEFT ARE THE LOOSE ELASTIC
BUCCAL ORAL MUCOSA BLENDING INTO THE DENSE FIRM
GINGIVA .ON THE RIGHT GINGIVA AND PALATE ARE
SIMILAR WITH DENSE FIRM COLLAGEN COVERED WITH
KERATINISED STRATIFIED SQUAMOUS EPITHELIUM
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ORAL MUCOSA
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THE ARROWS SHOW MUSCLE FIBERS SURROUNED BY LOOSE
ELASTIC CONNECTIVE TISSUE IN ORAL MUCOSA
ATTACHING TO CRESTAL BONE. ABOVE THIS THE
DENSE NON ELASTIC COLLAGEN OF THE GINGIVA RESISTS
MUSCLE PULL FROM MOVING THE GINGIVAL MARGIN AWAY
FROM THE TOOTH SURFACE THIS REULTS IN GINGIVAL
MARGIN STABILITY WITH NO PROGRESSIVE GINGIVAL
RECESSION
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THE FUNCTION OF GINGIVA IS DIFFERENT FROM ORAL
MUCOSA.GINGIVA MUST RESIST THE MECHANICAL STIMULI
OF COURSE FOOD PARTCLES IMPINGINGING ON IT
DURING MASTICATION AS WELL AS HAVING LARGE
ACCUMULATIONS OF PLAQUE BACTERIA IN DIRECT
CONTACT WITH THE GINGIVAL SULCUS.
GINGIVALTISSUE MUST FORM A SEAL IN THE SULCUS
THAT PROTECTS THE UNDERLYING TISSUE FROM SUB
GINGIVAL PLAQUE. ANDPREVENTS LOSS OF TISSUE FLUID.
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THE OUTER SURFACE OF GINGIVA IS COVERED WITH A
THICK LAYER OF KERATINISED SRATIFIED SQUAMOUS
EPITHELIUM WITH FINGER LIKE PROJECTIONS RETE
PEGS INTO THE DENSE COLLAGEN UNDERNEATH. THE
STRONG ATTACMENT OF COLLAGEN TO EPITHELIUM
BETWEEN THE RETE PEGS CAUSES THE GINGIVA TO
HAVE A STIPPLED SURFACE WHEN IT IS NORMAL AND
NOT INFLAMED
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THE TIP OF THE GINGIVAL CREST HAS AN OUTER LAYER
OF KERATIN WHILE THERE IS NO KERATIN ON THE
EPITHELIUM LINING THE GINGIVAL SULCUS
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THE BASAL LAYER IS ATTACHED TO THE BASEMENT
MEMBRANE BY HEMI DESMOSOMES. BASAL CELLS
PROLIFERATE AND PASS THROUGH THE VARIOUS LAYERS
UNTIL THEY REACH THE SURFACE AND HAVE BECOME
INACTIVE AND ARE DESQUAMATED OFF AS DEMOSOMES
FAIL TO HOLD THE CELLS TOGETHER. ON THE
KERATINISED OUTER GINGIVAL SURFACE THESE CELLS
HAVE LOST THEIR NUCLEI AND CYTOPLASMIC ORGANELLES
AND HAVE ACCUMULATED KERATIN GRANULES
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OUTER SURFACE OF GINIVA. TEN DAYS AFTER
LABELLING PROLIFERATING BASAL CELLS WITH H3
THYMIDINE MANY OF THE CELLS HAVE PASSED TO THE
OUTER SURFACE AND BECOMED KERATINISED .CELL
TURNOVER IS 10 TO 12 DAYS.
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ELECTRON MICROGRAPH 47,000 MAGNIFICATION OF
EPITHELEAL- CONNECTIVE TISSUE JUNCTION. Pv
pinocytotic vesicles of basal eptihelial cells
secreting glycoprotein laminin for the lamina
lucida layer of basement membrane. h lamina
densa layer type IV collagen from connective
tissue with adjacent epithelial attachent
organelle hemi-desmosome binding the epithelium
to the connective tissue.
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ELETRON MICROGRAH 32,000 MAGNIFICATION. SUPRA
BASILAR EPITHELIAL CELL WITH ACTIVE NUCLEUS,
MITOCHONDRIA , ENDO PLASMIC RETICULUM AND GOLGI
COMPLEX..
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ELECTRN MICROGRAPH SUB SURFACE EPITHELIAL CELL.
NO NUCLEUS, NO FUNCTIONING CYTOPLAMIC
ORGANELLES. PERIPHERY OF CELL STILL JOINED TO
ADJACENT CELLS BY DEMOSOMES, TIGHT JUNCTIONS AND
INTERMEDIATE JUNCTIONS,
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SURFACE EPITHELIAL CELL. NO CYTOPLASMIC NOR
NUCLEAR ACTIVITY. COTAINS LIPIDS AND
KERATINO-HYALINE DEPOSITS., HELD TO SUB-SURFACE
LAYER BY DESMOSOMES WITH NO TIGHT OR
INTERMEDIATE JUNCTIONS SURVIVING. CELL IS ABOUT
TO BE DESQUAMATED.
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IN SOME PATIENTS THE BASAL LAYER OF THE GINGIVA
CONTAINS MELANOCYTES--PIGMENT CONTAINING CELLS
WHICH GIVE A BROWNISH HUE TO PORTIONS OF THE
GINGIVA. THERE ARE ALSO AFEW CELLS IN THE
CONNECTIVE TISSUE WHICH HAVE TAKEN UP MELANIN
GRANULES -- MELANOPHORES.
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ANOTHER TYPE OF CELL FOUND IN NORMAL GINGIVA
ARE LANGERHANS CELLS . THESE CELLS HAVE
DENDRITIC EXTENSIONS AND ARE IN THE SUPRA BASILAR
LAYER.THEY FUNCTION AS ANTIGEN PROCESSING CELLS
AND ARE MODIFIED MACROPHAGES.
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ELECTRON MICROGRAPH OF A MERKEL CELL FOUND IN THE
DEEP LAYERS OF EPITHELIUM. THEY FUNCTION AS
TACTILE PROPRIOCEPTIVE CELLS AND ARE CONNECTED
TO NERVE FIBERS.
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THE CONNECTIVE TISSUE OF GINGIVA IS MADE UP OF
MAINLY TYPE 1 COLLAGEN BUNDLES WIH SOME TYPE 1V
FIBERS BETWEEN THE BUNDLES AND IN THE BASEMENT
MEMBRANE. THERE ARE AFEW ELASTIC FIBERS MADE UP
OF ELASTIN ELAUNIN AND OXYTALAN AMONG THE
COLLAGEN FIBERS. THE GROUND SUBSTANCE IS MAINLY
PROTEO GLYCANS---HYALURONIC ACID, CHONDROITIN
SULFATE AS WELL AS FIBRONECTIN A GLYCO PROTEIN
THERE ARE ALSO BLOOD VESSELS WHICH HAVE TERMINAL
LOOPS EXTENDING BETWEEN THE RETE PEGS .NERVES
PRESENT ARE MAINLY MYELINATED WITHTACTILE
RECEPTORS AND TEMPERATURE RECEPTORS
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SCANNING ELECTRON MICROGRAPH OF DENSE COLLAGEN
FIBERS OF GINGIVA
HEALTHY GINGIVA CONTAINS MANY FIBROBLASTS AND A
FEW INFLAMMATORY CELLS SUCH AS MACROPHAGES
,NEUTROPHILS, PLASMA CELLS AND LYMPHOCYTES.
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THE MAJOR GROUP OF GINGIVAL FIBERS ARE THE
GINGIVO DENTAL GROUP EMBEDDED IN CEMENTUM AND
FANNING OUT TO THE GINGIVAL MARGIN THE ELECTRO
MICROGRAPH SHOWS ORGANISED COLLAGEN FIBERS
ATTACHED TO CEMENTUM THERE ARE ALSO CIRCULAR
FIBERS IN A RING AROUND THE TOOTH AND
TRANSSEPTAL FIBERS BETWEEN ADJACENT TEETH
RUNNING HORIZONTALLY AND ATTACHED AT EACH END
TO THE CEMENTUM OF EACH TOOTH
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THE GINGIVAL SULCUS EXTENDS FROM THE GINGIVAL
MARGIN APICALLY TO THE CEMENTO-ENAMEL JUNCTION.
IT FORMS ASEAL AGAINST THE TOOTH AND ACTS AS A
BARRIER TO SUB GINGIVAL PLAQUE BACTERIA AND
PREVENTS FLUID LOSS FROM THE UNDER LYING
CONNECTIVE TISSUE
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THE CORONAL HALF OF THE GINGIVAL SULCUS IS LINED
BY THE SULCULAR EPITHELIUM.THIS IS A NON
KERATINISED STRATIFIED SQUAMOUS EPITHELIUM THAT
IS THINNER THAN THE OUTER GINGIVAL EPITHELIUM AND
IT SERVES AS A PROTECTIVE BARRIER. THE APICAL
HALF OF THE GINGIVAL SULCUS IS LINED BY THE
JUNCTIOAL EPITHELIUM WHICH ACTS AS ASEAL AGAINST
THE ENAMEL SURFACE.
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JUNCTIONAL EPITHELIUM. THIN LAYER OF CELLS 10 TO
20 CELLS THICK TAPERING TO 1 TO 2 CELLS AT
APICAL END. e enamel .BASAL CELLS AGAINST
CONNECTIVE TISSUE PROLIFERATE WITH TURNOVER RATE
OF 1 TO 6 DAYS. CELLS MIGRATE THROUGH TO BE
EXFOLIATED INTO THE GINGIVAL SULCUS. THE OUTER
SURFACE OF THIS EPITHELIUM FORMS A SEAL AGAINST
THE ENAMEL WITH A SECRETION OF A PROTEIN CUTICLE
LIKE SUBSTANCE AND PRESENCE OF HEMI- DESMOSOMES
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ELECTRON MICROGRAPH JUNCTIONAL EPITHELIUM 47,000
MAG ES enamel surface DL dental lamina. HD
hemidesmosome BL basal lamina M
mitochondria.THE OUTER CELLS OF JUNCTIONAL
EPITHELIUM HAVE A HIGHLY SPECIALISED FUNCTION--
THEY ARE METABOLICALLY ACTIVE, HAVE HEMI
DESMOSOMES SECRETE LAMININ AS A BASAL LAMINA AND
THESE TOGETHER WITH THE PROTEINS OF THE DENTAL
LAMINA ATTACH THE GINGIVA TO THE TOOTH AND FORM
A SEAL AT THE APICAL END OF THE GINGIVAL SULCUS,
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THE JUNCTIONAL EPITHELIAL SEAL IS ESSENTIAL FOR A
HEALTHY GINGIVA .IT IS DEPENDANT ON AN INTACT
EPITHELIAL LAYER AND AND THE STRONG ORGANISED
COLLAGEN GINGIVAL FIBERS THAT KEEP THE GINGIVA
IN INTIMATE CONTACT WITH THE TOOTH. A SIMILAR
ARRANGEMENT CAN OCCUR ON CEMENTUM ANB EVEN ON
DENTAL IMPLANTS.
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PALATAL MUCOSA
ON THE RIGHT SIDE IS THE PALATAL MUCOSA WHICH IS
CONTINUOUS AND SIMLIAR WITH THE GINGIVA IT IS
COVERED WITH STRATIFIED SQUAMOUS EPITHELIUM WITH
A HIGHLY KERATINISED SURFACE. AND HAS UNDER THIS
A DENSE LAYER OF COLLAGEN.
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HIGHER POWER VIEW OF PALATE. EPITHELIUM SAME AS
GINGIVA PROVIDES ATHICK PROTECTIVE COVER AGAINST
MECHANICAL. CHEMICAL AND THERMAL INSULTS THE
IMMEDIATE SUB MUCOSA IS DENSE COLLAGEN. AND BELOW
THIS IS A LOOSE CONECTIVE TISSUE THAT CONTAINS
MAJOR NERVES AND BLOOD VESSELS. IN THIS TISSUE
THERE ARE ADIPOSE CELLS IN THE ANTERIOR PART OF
THE PALATE AND ACCESORY SALIVARY GLANDS IN THE
POSTERIOR PART. IN THE DEEPEST LAYER THERE IS
PERIOSTEUM COVERING THE PALATAL BONE.
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