oral mucosa
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Oral Mucosa. Dr. Ali Tahir. Mucous membrane. Moist lining of GIT, Nasal passages & body cavities that communicate with the exterior The mucous membrane of oral cavity is called “Oral Mucosa” Located anatomically between skin & GIT mucosa & shows some properties of both - PowerPoint PPT PresentationTRANSCRIPT
Oral Mucosa
Oral MucosaDr. Ali TahirMucous membraneMoist lining of GIT, Nasal passages & body cavities that communicate with the exteriorThe mucous membrane of oral cavity is called Oral MucosaLocated anatomically between skin & GIT mucosa & shows some properties of bothBecause of its various functions, it is considered an organ
Dr. Ali Tahir, M.Phil (Part I)Functions of Oral MucosaProtectionFrom mechanical forces & abrasion while chewing food & from micro-organisms resident in the oral cavitySensationTemperature, Touch, Pain, TasteReceptors for Satisfaction of thirst, Swallowing, gagging, salivationSecretionMajor secretion is salivaMajor & minor salivary glandsSebaceous glands are frequently present (upper lip & buccal mucosa) sometimes called Fordyces spots but their secretions are insignificantMay be an accident of embryologic development
Dr. Ali Tahir, M.Phil (Part I)AnatomyTwo partsOuter vestibule (bounded by lips & cheeks)Oral cavity proper (separated from vestibule by teeth & gingiva)Superiorly bound by hard & soft palateInferiorly by floor of mouth & tonguePosteriorly by pillars of fauces
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)TypesLining MucosaConstitutes the large part (60%)Soft, pliableMasticatory mucosa25%Firm, immobileGingiva & hard palateSpecialized mucosaDorsum of tongue, in the form of papillaeUnique to oral cavity15%Dr. Ali Tahir, M.Phil (Part I)Clinical featuresOral mucosa is more deeply coloured compared to skinB/c of Concentrated & dilated blood vesselsThickness of epitheliumDegree of keratinizationAmount of melaninInflamed mucosa is more red b/c of dilation of blood vessels
Dr. Ali Tahir, M.Phil (Part I)ComponentsTwo main componentsStratified Squamous Epithelium (oral Epithelium)Lamina PropriaInterface b/w these two is irregular consisting of C.T papillae & rete ridges/pegsBasal lamina separates the two
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)Types & Layers of EpitheliumKeratinized EpitheliumHard palate gingiva & tongueBasal cell layerPrickle cell layerGranular cell layerKeratinized layerNon-keratinized EpitheliumBuccal mucosa, floor of mouth, ventral surface of tongueBasal cell layerPrickle cell layerIntermediate cell layerSuperficial cell layer
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)SubmucosaA layer of loose fatty or glandular connective tissue may be present between the oral mucosa & underlying bone/muscleThis layer contains blood vessels, nerves & minor salivary glandsComposition of submucosa determines the flexibility of the attachment of oral mucosa to underlying sturucturesEg, in gingiva & hard palate, oral mucosa is directly attached to periosteum & no submucosa is present. This is called mucoperiostium & is firm and inelasticDr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)Lymphoid tissueIn several regions, nodules of lymphoid tissue consisting of crypts formed by invaginations of the epithelium into the lamina propria are presentMostly present in posterior parts of oral cavityLingual tonsilsPalatine tonsilsPharyngeal tonsilsTogether form Waldeyers ringSmall nodules may also be present in soft palate, ventral surface of tongue & floor of mouthDr. Ali Tahir, M.Phil (Part I)Oral epitheliumConsist of tightly packed cells called keratinocytesMaintains its structural integrity by a continuous process of cell renewalTwo types of cell populationProgenitor cellsMaturing cellsCells produced by mitosis in the deeper layers (basal & parabasal layers) migrate to the surface layers
Dr. Ali Tahir, M.Phil (Part I)Epithelial proliferationDividing cells are present in clusters at the bottom of epithelial ridgesProgenitor population consists of two groupsStem cells (slow cell cycle)Produce basal cells & retain proliferative potential of tissueAmplifying cellsIncrease the no. of cells available for maturationAfter division, each daughter cell recycles in the progenitor population or enters the maturing populationTime required to replace all the cells in the epithelium is called Turnover time
Dr. Ali Tahir, M.Phil (Part I)Turn over timeWide range of estimates have been made52-75 days for skin4-14 days for gut41-57 days for gingiva25 days for cheekNon-keratinized epithelium turns over faster than the keratinized
Dr. Ali Tahir, M.Phil (Part I)SignificanceCancer chemotherapy drugs block the life cycle of cancer cells as well as normal host cellsCells with short turnover time are most affected. These includeBlood cells precursors in bone marrowIntestinal epitheliumOral epitheliumLeads to formation of oral ulcersIn addition, inflammation also affects rate of mitosisDr. Ali Tahir, M.Phil (Part I)Factors influencing the epithelial proliferationEpidermal growth factorKeratinocyte growth factorInterleukin-1Transforming growth factor and Dr. Ali Tahir, M.Phil (Part I)KeratinizationPresent on masticatory mucosa (hard palate, gingiva, parts of dorsal surface of tongue)Inflexible, tough, abrasion resistant, tightly bound to lamina propriaProcess of maturation is called keratinization or cornification
Dr. Ali Tahir, M.Phil (Part I)KeratinizationBasal cell layer (stratum basale)Cuboidal or columnar cells containing bundles of tonofibrils. Site of most cell divisionsPrickle cell layer (stratum spinosum)Larger, ovoid cells with conspicous tonofibril bundles, upper part of layer contains membrane-coating granulesGranular cell layer (Stratum granulosum)Flattened cells, keratohyaline granules associated with tonofibrilsKeratinized (stratum corneum)Extremely flattened & dehydrated cells with loss of all organells, cells filled with fibrillar material. If pyknotic nuclie retained, called para-keratinizedDr. Ali Tahir, M.Phil (Part I)Non-keratinizedBasal cell layer (stratum basale)Cuboidal/columnar cells containing separate tonofilamentsPrickle cell layer (stratum spinosum)Larger ovoid cells containing dispersed tonofilaments, membrane coated granules in upper part of layerIntermediate layer (stratum intermedium)Slightly flattened cells containing dispersed tonofilaments & glycogenSuperficial layer (stratum superficiale)Slightly flattened cells, dispersed tonofilaments, glycogen, fewer organelle, nuclie
Dr. Ali Tahir, M.Phil (Part I)Ultra structure of epithelial cellsCells of basal layer are least differentiated cellsContain organelles & certain structures such as tonofilaments & desmosomesTonofilaments are fibrous proteins & belong to the class of intermediate filamentsAggregate to form bundles called tonofibrilsChemically represent cytokeratins which are chracteristic constituents of epithelial cells
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)KeratinsRepresent a large family of proteinsClassified according to the molecular weight & charge. E.g..Low molecular weight (40kDa) found in glandular & simple epitheliaIntermediate molecular weight found in stratified epitheliaHigh molecular weight (67kDa) in keratinized stratified epitheliaKeratinzed epithelium hasType1, 5, 6, 10, 14, 16Non-keratinized epithelium hasType 4, 5, 13, 14, 19Dr. Ali Tahir, M.Phil (Part I)Adhesions & AttachmentsCohesion b/w cells is provided by protein-carbohydrate complexes produced by epithelial cells themselvesIn addition, modifications of adjacent cell membranes of cells called desmosomes provide attachment into which tonofilaments insertAdherence b/w epith & C.T is provided by hemidesmosomes which attach the cells to basal laminaDr. Ali Tahir, M.Phil (Part I)Adhesions & AttachmentsTwo other types of connections areGap junctionsTight junctionsGap junction:Membranes of adjacent cells run closely together separated by a small gapSmall interconnections are presentGap junctions allow electric/chemical communicationTight junctionAdjacent cell membranes are tightly apposed
Dr. Ali Tahir, M.Phil (Part I)Membrane-coated granulesAlso called lamellate granulesAre small memrane bound structures about 250nm in size containing glycolipid, originate from golgi complexAppear in the upper part of prickle layerThey are elongated in keratinized & circular in non-keratinized epitheliumIn the upper part of stratum granulosum/intermedium, these granules appear to fuse with superficial cell membrane to discharge their contents into intercellular spaceDr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)Cell Maturation in Keratinized epithCells in the superficial part of granular layer develop a thickening on the intra-cullular aspect of their membraneIt contributes in resistance of keratinized layer to chemical solventsOne of the major constituent of this thickening is a protein called involucrin
Dr. Ali Tahir, M.Phil (Part I)Granular layerFound in keratinized epitheliumContains keratohyalin granules, which are basophilic granules under light microscopeThese are irregular in shape0.5-1nm in sizeSynthesized by ribosomesIntimately associated with tonofibrilsFacilitate aggregation & formation of cross-links b/w cytokeratin filamentsProteins making bulk of these granules are called Loricrin
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)SquamesAs the cells of granular layer reach the junction with the keratinized layer, a sudden change occursAll organelles are lost, including nuclie & keratohyalin granulesCells dehydrate & assume the shape of hexagonal disksThese are called squamesSquames are lost within days, a process called desquamation & replaced by cells from underlying layersLimit the colonization of pathogenic micro-organismsKeratin layer in oral cavity may be upto 20 layers of squames
Dr. Ali Tahir, M.Phil (Part I)Cell maturation in non-keratinized epitheliumA slight increase in size occurs in intermediate cell layerAccumulation of glycogen in cells of surface layerOccasionally keratohyalin granules are seen but these arent associated with tonofilamentsThese granules may remain upto the surface layer
Dr. Ali Tahir, M.Phil (Part I)Non-keratinized epitheliumCells in the superficial layer are slightly more flattenedContain dispersed tonofilaments, retain nuclie & do not dehydrateThus are tolerant to compression & distension
Dr. Ali Tahir, M.Phil (Part I)Anatomical variationsSome variation of anatomical locations of keratinized & non-keratinized epithelium may occurHyperkeratosis of keratinized oral epithelium is physiological to chronic irritationHyperkeratosis of non-keratinized epithelium can be associated with abnormal cellular changes that can lead to cancerInflammation of gingiva can lead to loss of keratinization or parakeratinizationThese changes are usually reversible when irritant is removedDr. Ali Tahir, M.Phil (Part I)Permeability & absorption of oral epitheliumOral epithelium is largely impermeable & lacks absorptive capacityEpithelium at the floor of the mouth, however, is thin & more permeable comparatively (Nitroglycerin to relieve angina pain)Oral epithelium thus limits the absorption of toxins from micro-organisms except in dentogingival junctionDr. Ali Tahir, M.Phil (Part I)Other cells in oral epitheliumMelanocytesPresent in basal layerLack desmosomes & tonofilamentsDendritic, synthesis of melanin pigment granules (melanosomes)Merkel CellsPresent in basal layerNon-dendritic, tactile sensationLangerhans cellsDendriticPresent in parabasal layerAntigen trapping & processingLymphocytesVariable locationInflammatory responseB or T cellsDr. Ali Tahir, M.Phil (Part I)PigmentationTwo types of pigmentation is seen in oral mucosaEndogenousExogenousEndogenous pigments in oral mucosa are melanin & hemoglobinMelanocytes are derived from neural crest ectodermEnter the epithelium at 11th week of gestationMelanosomes are injected into adjacent keratinocytes by long dendritic processes that often pass through several layers of epitheliumGroups of melanosomes can be seen under light microscope, called melanin granulesDr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)PigmentationLight & dark individuals have the same number of melanocytes, the difference results from the activity of melanocytesIn persons with heavy melanin pigmentaion, melanophages are seen in the connective tissueIn oral mucosa, melanin pigmentation is most commonly seen in gingiva, buccal mucosa, hard palate & tongue & is more in dark skinned individuals
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)Pigmented pathologiesOral melanotic maculeIncreased production of melanin pigment without proliferation of melanocytesNevus (Mole)Benign proliferation of melanocytesMelanomaMalignant tumour of melanocytesMelanoma of oral cavity is aggressiveDr. Ali Tahir, M.Phil (Part I)PigmentationExogenousCaused by foreign material introduced locally or systemicallyOne of the most common oral exogenous pigment is amalgumGives rise to bluish-gray patch called amalgum tattooSystemic administration of metals such as lead & bismuth can cause gingival margin pigmentation (called Burtons line)Dr. Ali Tahir, M.Phil (Part I)MCQsStratum distendum is another name forSubmucosa of lining oral epitheliumPrickle layer of non-keratinized epitheliumSuperficial layer of Non-keratinized epitheliumGranular layer of keratinized epitheliumDr. Ali Tahir, M.Phil (Part I)MCQsThe superficial cells of granular layer of keratinized oral epithelium have intra-cellular thickenings to resist chemical solvents containing which proteins?CytokeratinsGlycoproteinsInvolucrinFilaggrinDr. Ali Tahir, M.Phil (Part I)MCQsBlood flow in oral mucosa is the greatest in which regionSoft palateFloor of mouthGingivatongueDr. Ali Tahir, M.Phil (Part I)MCQsIn infants, Suckling Pad refers toA thickened vermillion zoneA thickened intermediate zone A thickened labial mucosaA thickened muco-cutaneous junctionDr. Ali Tahir, M.Phil (Part I)MCQsDr. Ali Tahir, M.Phil (Part I)Dr. Ali Tahir, M.Phil (Part I)