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Jeena Sara Paul 15th Jan 2009 Ist year MDS 9.00 AMChristian Dental College Ludhiana
The moist lining of the oral cavity that is in continuation with the exterior surface of skin on one end and oesophagus on the other end is called the oral mucosa or oral mucous membrane.
It is protective mechanically against both compressive and shearing forces. It provides a barrier to microorganisms , toxins and various antigens. It has a role in immunological defence, both humoral and cell- mediated. Minor glands within the oral mucosa provide lubrication and buffering as well as secretion of some antibodies. The mucosa is richly innervated, providing input for touch, proprioception, pain and taste. Reflexes such as gagging, retching and salivating are initiated by receptors in the oral mucosa.
Primitive oral cavity develops by fusion of embryonic stomatodeum with foregut after rupture of buccopharyngeal membrane at 26 days IU Structures from branchial arches like tongue epiglottis and pharynx covered by epithelium derived from endoderm Epithelium covering palate cheeks and gingivae of ectodermal origin
5-6 weeks: 2 layers of cells have formed lining oral cavity 8 weeks: thickening in area of vestibular dental lamina complex, extracellular reticular fibres accumulate 10-14 wks: cellular degeneration forming oral vestibule 8-11 wks Palatal shelves elevate and close. Capillary buds and collagen fibres detected At this time morphology of future mouth is apparent
7 wks: circumvallate and foliate papillae appear followed by fungiform . 10 wks: filiform papillae appear 10-12 wks: future lining and masticatory mucosa stratification of epithelium and different morphology Areas destined to become keratinised have darkly staining columnar basal epithelium Epithelial cells in areas of future lining mucosa retain cuboidal cells
13-20 wks: all oral epithelia thicken with appearance of sparse keratohyalin granules Melanocytes and langerhans cells appear Surface layers show parakeratinisation; orthokeratosis occurs only after eruption of teeth post-natally 17-20 wks: completely formed with appearance of elastic fibres in the ectomesenchyme
The oral cavity consists of 2 parts: outer vestibule (bounded by lips and cheek) oral cavity proper (separated by alveolus bearing teeth and gingivae). Superiorly: hard and soft palate Inferiorly: floor of mouth, base of tongue Posteriorly: pillars of fauces, tonsils
3 main types of mucosa Masticatory Lining Specializedidentified mucosa Mucosa Mucosaaccording (60%) (25%) (15%) to their primary function:
Although continuous with skin, oral mucosa differs in a number of ways. Colour: Oral mucosa is more deeply coloured, most obviously at the lips. Concentration and state of dilatation of blood vessels. Thickness of epithelium Degree of keratinisation Amount of melanin pigment
Moist surface and absence of appendages. Glandular component of oral mucosa represented by minor salivary glands. Occasional sebaceous glands in upper lip and buccal mucosa: Fordyces spots. Smoother surface and fewer wrinkles. Papillae on dorsum of tongue. Transverse ridges of palate
Stratified squamous epithelium: oral epithelium (epidermis) Connective tissue layer: Lamina Propria (dermis) Interface: Upward projections of connective tissue- Connective tissue papillae interdigitate with epithelial ridges- Rete ridges or rete pegs Typical haematoxylin-eosin stain shows this interface as a structure less layer about 1-2 microns thick- basement membrane.
The junction between oral epithelium and lamina propria is obvious, unlike that between oral mucosa and underlying tissue. Oral mucosa has no muscularis mucosae. In cheeks, lips and parts of hard palate, a layer of loose fatty glandular tissue containing vessels and nerves supplying the mucosa separates the oral mucosa from underlying bone or muscle: Submucosa In gingiva and parts of hard palate, oral mucosa directly attached to underlying bone. This provides a firm inelastic attachment: Mucoperiosteum
Minor salivary glands in submucosa Sebaceous glands in lamina propria produce sebum said to lubricate the surface of the mucosa. This might actually be an embryologic anomaly. Nodules of lymphoid tissue are present in various areas consisting of crypts formed by invaginations of epithelium into lamina propria. Capillaries carry adhesion molecules like: Endothelial cell leukocyte adhesion molecule Intercellular adhesion molecule Vascular cell adhesion molecule These facilitate trafficking of leukocytes (lymphocytes and plasma cells) from blood. Found as lingual, palatine and pharyngeal tonsils forming Waldeyers ring. Small nodules also in soft palate, ventral surface of tongue, floor of mouth.
Constitutes primary barrier between oral environment and deeper tissues. The oral epithelium is a stratified squamous epithelium consisting of cells tightly attached to each other and arranged in a number of distinct strata. Maintains its structural integrity by a process of continuous cell renewal. Cells produced by mitotic divisions in deepest layers replace those that are shed. Thus there are 2 populations of cells: A progenitor population A maturing population
In thin epithelia, progenitor cells seen in basal layer In thicker epithelia, seen in lower 2-3 cell layers Studies on epidermis and oral epithelium indicate that progenitor compartment consists of 2 functionally distinct subpopulations: A small population of slowly cycling stem cells: Retains proliferative potential A larger population of amplifying cells: increases number of cells available for maturation Turnover time: time taken for a cell to divide and pass through the entire thickness of epithelium. 52-75 days in skin 4-14 days in gut 41-57 days in gingiva 25 days in cheek
OUTER SURFACE OF GINGIVA. TEN DAYS AFTER LABELLINGPROLIFERATING BASAL CELLSWITH H3 THYMIDINE MANY OF THE CELLS HAVEPASSED TO THE OUTER SURFACEAND BECOMED KERATINISED.CELL TURNOVER IS 10 TO 12DAYS.
Mitotic activity affected by: Epidermal growth factorKeratinocyte growth factor Interleukin 1Transforming growth factors Time of the day Stress Inflammation
2 main patterns: keratinisation and nonkeratinization Keratinisation: Inflexible, tough, resistant to abrasion and tightly bound to lamina propria The mucosal surface results from formation of a surface layer of keratin and process of maturation is called keratinisation or cornification. Shows 4 stratae: Stratum basale Stratum spinosum Stratum granulosum Stratum corneum
Basal layer- layer of cuboidal or columnar cells adjacent to basement membrane Stratum spinosum- several rows of larger elliptical or spherical cells also known as prickle cell layer. Cells aligned such that they remain in contact only at points known as desmosomes or intercellular bridges Stratum granulosum- Larger flattened cells with small granules that stain intensely with acidic dyes. Stratum corneum- The surface layer composed of flat cells called squames that stain bright pink with eosin and has no nuclei. The pattern of maturation of these cells is called orthokeratinization Parakeratinisation is a variation of keratinisation seen in masticatory mucosa. The surface layer stains for keratin but pyknotic nuclei are retained in some or all squames. Keratohyalin granules present but fewer granules
Non keratinisation Lips, buccal mucosa, alveolar mucosa, soft palate, underside of tongue, floor of mouth Sometimes thicker than keratinised mucosa Epithelium of cheek more than 500 m thick with broader epithelial ridges Stratae: Stratum basale Stratum intermedium Stratum superficiale/ distendum
An important property of any epithelial cell is its ability to function as a barrier. This is brought about by tonofilaments, desmosomes and hemidesmosomes. Ceramides, cholesterol and long chain fatty acids also regulate the membrane permeability Characteristic structures for epithelial cells include: Filamentous strands called tonofilaments Intercellular bridges or desmosomes
Tonofilaments Fibrous proteins synthesized by ribosomes Long filaments with diameter of 8nm Chemically cytokeratins CKs function as components of cytoskeleton and cell contacts. All stratified oral epithelia possess CK 5 and 14. Keratinised oral epithelium contain Ck 1,6,10,16. Non keratinised contains 4,13 and 19. May be important in maintaining metabolic homeostasis of cell. Recent research on keratins and cell surface markers has focussed on early identification of aberrant maturation like in case of cancer.
Desmosomes or macula adherens are circular or oval areas of adjacent cell membranes, adhering by intracellular thickenings: attachment plaques and containing proteins: desmoplakin and plakoglobin. Cadherins penetrate the membrane and enter the intercellular region of desmosome. Hemidesmosomes are present on cells of basal layer and provide adhesion between epithelium and connective tissue Studies indicate that desmosomes and hemidesmosomes differ in their molecular constituency. When these are disturbed like in pemphigus, there is epithelial or sub epithelial splitting of the epithelial cells
Gap junction or nexus is a region where membranes of adjacent cells run closely together; separated by a small gap. They allow electrical or chemical communication between cells.
Tight junction or occluding junction is so tightly apposed such that intercellular space is absent.
The major changes involved are Change in cell size and shape Synthesis of structural proteins and tonofilaments Appearance of new organelles Production of additional intracellular material.
Membrane coating or lamellate granule: Small membrane bound structures in spinous cell layer about 250 nm in size and contains glycolipids formed in Golgi bodies
KERATINISED EPITHELIUM NONKERATINISED EPITHELIUM Increase in size from basal Greater increase in cell size layer to prickle cell layer Tonofilaments dispersed and Tonofilaments aggregated in less conspicuous bundles to form tonofibrils Lamellate granules appear Lamellate granules are circular with amorphous elongated and contain a content series of parallel lamellae The contents of these have a The contents of these different lipid composition granules are discharged to and forms a less effective form a lipid rich permeability barrier barrier
Cells in superficial part of granular layer develop a noticeable thickening on the inner surface of cell membrane formed by proteins like involucrin. This contributes to the resistance of keratinised layer to chemical solvents. A similar but less obvious thickening is seen in surface cells of non keratinised epithelia.
Keratohyalin granules of the granular cell layer are characteristic in keratinised epithelium. They have mainly the protein filaggrin and a sulphur rich compound loricrin thought to facilitate aggregation and formation of cross-links between cytokeratin filaments of keratin layer. As they reach the junction with keratinised layer, the organelles disappear, the cells dehydrate, flatten, form hexagonal disks called squames and get packed with filaments cross linked by disulfide bonds. Squames are lost by a process of desquamation and replaced by cells from underlying layers.
The keratinised layer in oral cavity is composed of up to 20 layers of squames. The tightly packed cytokeratins within an insoluble tough envelope makes the layer resistant to mechanical and chemical damage. The surface layer of nonkeratinised epithelium consists of cells with loosely arranged filaments that are not dehydrated. Thus they form a surface that is flexible and tolerant of compression and distension.
Suprabasilar cell with active nucleiSubsurface epithelial cell withtight junctions and gap junctions
Histologic sections of oral epithelium show cells with dark nuclei surrounded by a light halo: Clear cells Make up 10% of cell population Include melanocytes, Langerhans cells, Merkel cells and inflammatory cells All except Merkel cells lack desmosomal attachments They have lesser number of tonofilaments and desmosomes None undergo epithelial maturation
2 types of pigmentation: endogenous and exogenous The main endogenous pigments involved with oral pigmentation are melanin and haemoglobin Melanin is produced by melanocytes found in basal cell layer of oral epithelium and epidermis Formed from neural crest ectoderm; found in epithelium at 11th week of gestation They divide and maintain themselves as a separate population. Melanin secreted in the form of melanosomes Macrophages that have taken up melanosomes appear dark and are called melanophages Pigmentation seen in gingiva, buccal mucosa, hard palate, tongue
THE BASAL LAYER OF THEGINGIVA CONTAINSMELANOCYTES—PIGMENT CONTAINING CELLSWHICH GIVE A BROWNISH HUE TOPORTIONS OF THE GINGIVA.THERE ARE ALSO A FEW CELLS INTHE CONNECTIVE TISSUE WHICHHAVE TAKEN UP MELANINGRANULES -- MELANOPHORES.
Dendritic cell seen above basal layer Contains small rod or flask shaped granule: Birbeck granule Revealed under EM with ATP stain They form in bone marrow and appear at 11th month IU Immunologic function recognising and processing antigenic material and presenting it to T lymphocytes They can migrate from epithelium to regional lymph nodes
THESE CELLS HAVEDENDRITIC EXTENSIONSAND ARE IN THE SUPRABASILAR LAYER.THEY FUNCTION ASANTIGEN PROCESSINGCELLS AND AREMODIFIEDMACROPHAGES.
Situated in basal layer NOT Dendritic; contain keratin tonofilaments and desmosomes Said to arise from division of an epithelial cell Has small membrane bound vesicles in cytoplasm, sometimes situated adjacent to a nerve fibre These granules release a transmitter across the synapse like gap between it and the nerve fibre triggering impulse Sensory and respond to touch
ELECTRON MICROGRAPH OF AMERKEL CELL FOUND IN THEDEEP LAYERS OFEPITHELIUM.THEY FUNCTION ASTACTILE PROPRIOCEPTIVECELLS AND ARE CONNECTEDTO NERVE FIBERS.
These include lymphocytes most commonly; PMNLs and mast cells also seen Usually seen associated with Langerhans cells A few inflammatory cells can be considered a normal component of the oral mucosa
Keratinocytes produce cytokinesMSH acts onmelanocytes - > CKspigmentation modulate function of Inter relation of Langerhans cells keratinocytes and nonkeratinocytes IL-1 activates T lymphocytes Langerhans and increases cells produce no of receptors CKs such as IL- to MSH 1
The junction of epithelium and lamina propria is an undulating interface at which the papilla of the connective tissue interdigitates with the epithelial ridges. This arrangement increases the surface area of the attachment enabling applied forces to be dissipated over a greater area. Masticatory mucosa has a greater no. while lining mucosa has lesser and shorter undulations This junction is also important for metabolic exchange as the epithelium has no blood vessels
In histological sections, (BM) basement membrane between epithelium and connective tissue appears as a structure less band and stains with PAS stain.
Lamina lucida: Bullous pemphigoid antigen Laminin Lamina densa (45 nm thick) Type IV collagen in chicken wire configuration Anchoring fibrils (50 nm thick) Type VII collagen Collagen of connective tissue: Type I Type III
Hemidesmosomes represent condensations of bullous pemphigoid antigen and intermediate filament associated protein Cytokeratin filaments loop into the hemidesmosomes Proteins of integrin family traverse the membrane and enter the lamina lucida Inserted into lamina densa are small loops of finely banded fibrils called anchoring fibrils
The connective tissue supporting the oral epithelium Divided for descriptive purpose into Superficial papillary layer: Collagen fibres thin and loosely arranged Several capillary loops present Deeper reticular (meaning netlike) layer: Collagen fibres arranged in thick bundles Parallel to surface Lamina propria consists of cells, vessels, neural elements and fibres embedded in amorphous ground substance.
Fibroblasts: Principal cell Responsible for maintaining tissue integrity by regulating cell turnover LM: cigar shaped(fusiform) or star shaped(stellate) with long processes that lie parallel to collagen fibres Nuclei contain 1 or more prominent nucleoli EM: Numerous mitochondria, extensive granular ER, prominent golgi complex and numerous membrane bound vesicles Low proliferation except in wound healing Participates in wound contraction In certain cases like gingival overgrowth, secrete more ground substance than normal
Macrophages Histiocyte LM: stellate or fusiform cell EM: Smaller and denser nuclei; less granular ER, cytoplasm contains lysosomes Ingests damaged tissue or foreign material in phagocytic vacuoles Processing of ingested material may be important in increasing antigenicity before it is presented to lymphocytes 2 types: melanophage and siderophage –resultant brownish colour appears clinically as a bruise
Mast cells Large spherical/elliptical mononuclear cell Contains large number of intensely staining granules that occupy its cytoplasm. Stain with basic dyes due to presence of heparin and histamine Found in association with small blood vessels Said to maintain normal tissue stability and vascular homeostasis
Inflammatory cells: Present in CT in the event of an injury or as part of a disease process When in significant numbers, they influence the behaviour of overlying epithelium by releasing cytokines Acute conditions: PMNLs Chronic conditions: lymphocytes, plasma cells monocots and macrophages
Collagen: Type I and Type III in lamina propria Type IV and VII in basal lamina Type V in inflamed tissue Elastic fibres: Elastin is responsible for elastic properties of fibre Second is a glycoprotein with microfibrillar morphology Initially elastic fibres consist entirely of microfibrils till they mature and get replaced by elastin
Consists of heterogenous protein-carbohydrate complexes permeated by tissue fluid Chemically proteoglycans and glycoproteins Proteoglycans: Polypeptide core with attached GAGs- hyaluronan, heparan sulphate, versican, decorin, biglycan and syndecan Interaction of these with cell surface molecules (integrins) important in modulating behaviour and function of cell Glycoproteins: Branched polypeptide chain to which few simple hexoses are attached.
Blood supply of oral mucosa is rich and much more profuse than skin. Blood supply greatest in gingiva Human oral mucosa lacks arteriovenous shunts but has rich anastomoses of arterioles and capillaries contributing to its ability to heal more rapidly than skin after an injury.
Oral region Sub-terminal branchesUpper lip Superior labial arteryUpper gingiva: Anterior Anterior superior alveolar artery, Lingual Major palatine artery Buccal Buccal artery Posterior Posterior superior alveolar arteryHard palate Major palatine artery, Nasopalatine artery Sphenopalatine arterySoft palate Minor palatine arteryCheek Buccal artery, Tl branches of facial artery Posterior alveolar artery, Infraorbital arteryLower lip Inferior labial artery, Mental artery, Br of inferior alveolar arteryLower gingiva: Ant buccal Mental artery Ant lingual Incisive artery, Sublingual artery Post lingual Inferior alveolar artery, Sublingual artery Post buccal Inferior alveolar artery, Buccal arteryFloor of mouth Sublingual artery, Br of lingual arteryTongue: Ant two thirds Deep lingual artery Posterior third Dorsal lingual artery
Because mouth is the gateway to the respiratory and alimentary tracts, it is richly innervated The supply is overwhelmingly sensory Efferent supply is autonomic, supplies blood vessels and minor salivary glands and may modulate activity of sensory receptors: 2nd ,3rd divisions of trigeminal nerve Afferent supply is from facial, glossopharyngeal and vagus nerves The sensory nerves lose their myelin sheaths and form a network in reticular layer of lamina propria Sensory nerves terminate in free and organised nerve endings These specialised nerve endings have been grouped according to morphology as Meissners/Ruffinis corpuscles, Krausses bulbs and mucocutaneous end organs
Sensory nerve networks more developed in oral mucosa lining anterior than in posterior regions of mouth ‘Touch’ more acute in tip of tongue and hard palate Touch receptors in soft palate and pharynx help initiate reflexes like swallowing, gagging and retching Temperature reception more acute in vermillion border, tip of tongue and ant hard palate.
Lip has skin on outer surface and labial mucosa on inner surface Between these tissues lie vermillion/red/transition zone Lips have striated muscle that are part of muscles of facial expression Minor mucous salivary glands in submucosa beneath oral mucosa Skin on outer surface is similar to skin elsewhere with a keratinised layer of epithelium on a bed of connective tissue
Lacks appendages of skin Occasional sebaceous glands at corner of mouth Requires constant moistening to prevent drying Epithelium: keratinised but thin and translucent CT papillae of lamina propria long, narrow; has capillary loops Hence the red colour
Inner surface of lip Covered by relatively thick non keratinised epithelium Wide lamina propria Short irregular papillae Submucosa with minor salivary glands Dense CT strands bind mucosa to underlying orbicular is ores Sebaceous glands may be present in cheek as Fordyces spots
Covers areas like hard palate and gingiva which are exposed to compressive and shear forces and to abrasion during mastication of food. Epithelium: moderately thick, frequently orthokeratinised though areas of parakeratinisation may be seen Junction between epithelium and lamina propria: convoluted with numerous elongated papillae Lamina propria: thick, contains dense network of collagen fibres as large closely packed bundles enabling mucosa to resist heavy loading
Covers immobile structures like palate and alveolar processes by direct firm attachment to periosteum to form mucoperiosteum OR indirectly by a fibrous mucosa Lat regions of palate show fat and glandular tissue interspersed with fibrous mucosa to cushion mucosa and protect vessels and nerves
Part of the oral mucosa that covers Alveolar process of the jaws and surrounds the neck of the teeth. Divided anatomically into: Marginal gingiva: Terminal edge or border of gingiva surrounding teeth in collar like fashion Attached gingiva: Continuous with marginal gingiva. Width of attached gingiva is distance between mucogingival junction and the projection of gingival sulcus or periodontal pocket
Width of attached gingiva greatest in incisor region: 3.5-4.5 mm in maxilla 3.3-4.9 mm in mandible Least in premolar region: 1.9 mm in maxilla 1.8 mm in mandible Width is least in children and increases with age
Gingival sulcus: Shallow v shaped crevice or space coronal to attachment of junctional epithelium Normally 0.5 – 3 mm with avg of 1.8 mm Depth> 5 mm is called periodontal pocket When the tooth first becomes functional, it lies at the cervical half of crown. It contains sulcular fluid, desquamated cells, neutrophils
Interdental gingiva: occupies gingival embrasure It can be: Pyramidal Col- Valley like depression that connects facial and lingual papilla
Oral epithelium: It covers the crest and outer surface of marginal gingiva and surface of attached gingiva. Sulcular epithelium: It lines the gingival sulcus. It is thin, non keratinised SSE without retepegs and extends from coronal limit of junctional epithelium to crest of gingiva.
Junctional epithelium: It consists of collar like band of non keratinised SSE. It is attached to tooth surface with basement membrane.
• After enamel formation is complete, enamel is covered with reduced enamel epithelium attached to tooth by hemidesmosomes and basal lamina.• During eruption, tip of tooth approaches oral mucosa causing REE and oral epithelium to meet and fuse.• Once tip of crown has emerged, REE is termed junctional epithelium.• As the tooth erupts, REE grows shorter; a shallow groove develops between the gingiva and tooth surface to form the sulcus.
The attachment ofjunctional epitheliumto tooth is reinforcedby gingival fibreswhich brace thegingiva against thetooth surface. Hencecalled dentogingivalunitA. DentogingivalfibresB. Longitudinal fibresC. Circular fibresD. AlveologingivalfibresE. Dentoperiostealfibres
F. Transseptal fibres G. Semicircular fibres H. Transgingival fibres I. Interdental fibres J. Vertical fibres
1. Supraperiosteal arterioles along facial and lingual surfaces of alveolar bone2. Vessels of periodontal ligament extending into gingiva and anastomosing with capillaries in sulcus3. Arterioles which emerge from crest of interdental septa to anastomose with vessels of PDL, capillaries in gingival crevicular area and vessels that run over alveolar crest
Terminal branches of periodontal nerve fibres Br of infraorbital or palatine, or lingual mental and buccal nerves
• Hard palateIt shows various zones:• Gingival region adjacent to tooth• Palatine raphe extending from incisal papillae posteriorly• Anterolaeral area or fatty zone• Posterolateral area or glandular zone between raphe and gingiva
Underside of tongue, inside of lips, cheeks, floor of mouth, alveolar processes far as gingiva and soft palate Epithelium: thicker than masticatory mucosa (>500 µm) , nonkeratinised Surface flexible, can withstand stretching Interface with CT: Smooth with slender CT papillae Lamina propria: thicker, fewer collagen fibres which follow irregular course between anchoring points
Assoc with elastic fibres to control extensibility of mucosa Where lining mucosa covers muscle, it is attached by a mixture of collagen and elastic fibres As mucosa slacks with movement, the elastic fibres retract mucosa and prevents injury by biting Submucosa: thick and loosely attached in alveolar mucosa and floor of mouth: underside of tongue- firmly attached
Clinical considerations: Lining mucosa is soft and pliable; Gingiva and hard palate covered by firm immobile layer. Local injections: fluid introduced easily into loose lining mucosa; injection into masticatory mucosa is difficult and painful. Biopsy/wounds: Lining mucosa gapes and requires suturing; masticatory mucosa does not. Inflammation: Accumulation of fluid obvious and painful in masticatory mucosa; in lining mucosa, the fluid disperses and inflammation not that evident or painful.
Mucosa of dorsal surface of tongue covered functionally by masticatory mucosa It has, in addition, different types of lingual papillae which possess a mechanical or sensory function
Cover the entire anterior part of tongue Cone shaped structures with a core of CT covered by a thick keratinised epithelium Form a tough abrasive surface to help in compressing and breaking food when tongue is apposed to hard palate Build-up of keratin results elongation of papillae in some patients: Hairy tongue LP- lamina propria SM- submucosa Mf - myofibrils
Single fungiform papillae scattered between numerous filiform papillae at tip of tongue Smooth round structures Appear red high vascular CT core visible through a thin nonkeratinised covering epithelium Taste buds present in epithelium on superior surface
Leaf like papillae Seen on lateral margins of posterior part of tongue More frequently in mammals other than humans Pink papillae 4-11 parallel ridges that alternate with deep grooves in mucosa Taste buds in epithelium of lateral walls of ridges
Adjacent and anterior to sulcus terminalis 8-12 in number Large structures surrounded by deep circular groove Ducts of von Ebner glands open into these grooves Have a CT core covered superiorly by keratinised epithelium Epithelium of lateral walls is non keratinised, contains taste buds
Barrel shaped structure composed of 30-80 spindle shaped cells Cells separated from underlying CT by basement membrane Apically , terminates just below the epithelial surface in a taste pit that communicates with surface through a taste pore 3 types of cells: Type I- light, most common Type II- dark, contain vesicles, adj to intra epithelial nerves Type III-intermediate
Replaced continually Presence depends upon presence of a functional gustatory nerve Taste bud cells and merkel cells are the only truly specialised cells in oral mucosa Regions: Sweet at tip, salty and sour on lateral aspects, bitter and sour at posterior region
Generation of taste stimuliAdsorption of molecules onto membrane receptors on surface of taste bud cells Activation of signalling cascade: release of TRANSDUCIN, GUSTDUCIN Change in membrane polarisation Release of transmitter substance Stimulation of unmyelinated nerve fibres of glossopharyngeal nerve
Smelly fruitThe durian fruit smellshorrible. Some people cannotbear to eat it because it smellsso foul. But it is called the"King of Fruits" and tastesdelicious. It is very large (canbe the size of a football) andcomes from South East Asia
The skin with hair follicles and sebaceous and sweat glands is continuous with the oral mucosa at the lips Epithelium keratinised, with thin long CT papillae containing capillary loops This brings blood close to the surface and gives strong red coloration called red /vermillion zone The line separating vermillion zone from skin of lip called vermillion border. In young persons, this border demarcated sharply, later becomes diffuse
Vermillion zone lacks salivary glands, contains only a few sebaceous glands, it tends to dry out, becomes cracked and sore in cold weather Between vermillion zone and thicker non keratinised labial mucosa is an intermediate zone covered by parakeratinised epithelium In infants this region is thickened and more opalescent: suckling pad
Although masticatory mucosa meets lining mucosa at more than 1 site, most abrupt is between attached gingiva and alveolar mucosa Identified clinically by indentation called mucogingival groove and by change from bright pink of alveolar mucosa to paler pink of gingiva Epithelium of attached gingiva is keratinised or parakeratinised Lamina propria contains numerous coarse collagen bundles attaching tissue to periosteum; reflected clinically as stippling
The structure of mucosa changes at mucogingival junction where alveolar mucosa has thicker nonkeratinised epithelium over loose lamina propria with numerous elastic fibres extending into thick submucosa
Region where oral mucosa meets surface of tooth Important because it represents a potential weakness in the otherwise continuous epithelial lining Principal seal between epithelium and enamel In germ free animals and in strictly healthy plaque free gingivae, sulcus is absent and gingival margin corresponds to coronal extent of junctional epithelium In avg human mouth, gingival sulcus has a depth of 0.5-3 m with an avg of 1.8 mm
The basic considerations in oral mucosa are variation in tissue colour, dryness, smoothness or firmness and bleeding tendency of gingiva Periodontal pocket: It is a pathologically deepened gingival sulcus as a response to plaque toxins and subsequent immunologic response. Restorative dentistry: In young patients, when the clinical crown is smaller than the anatomic crown, it is difficult to prepare a tooth for an abutment or crown. The restoration may require replacement when the crown is fully exposed
Gingival recession: May result in cemental /root caries and sensitivity of the exposed dentin Keratinisation of gingiva: Can be achieved by massage or brushing thus helping in stimulation and minimising plaque accumulation Discoloration of gingiva: Metal poisoning by lead or bismuth causes characteristic discoloration. Blood dyscrasias can be diagnosed by characteristic infiltration of the oral mucosa. Viral diseases like measles manifest as typical lesions of oral mucosa
Changes of tongue: In scarlet fever, atrophy of lingual mucosa causes peculiar redness of Strawberry tongue. Systemic diseases such as vitamin deficiencies lead to typical changes as Magenta tongue and beefy red tongue. Macule: A flat spot/stain/discoloration of the oral mucosa. Amalgam tattoo, nevus, rash of secondary syphilis Papule: Small rounded pimple like variably coloured. White variably patterned elevations of Lichen planus
Plaque: Slightly raised clearly demarcated area that may be smooth pebbly cracked or fissured. Leukoplakia, Erythroplakia Vesicle: Small circumscribed elevated blister not more than 5 mm in diameter with covering layer of epithelial cells and containing an accumulation of fluid. Herpes labialis Pustule: Vesicle predominantly containing pus
Bulla: Large vesicle or blister. Pemphigus and drug rections. May appear white due to necrosis of epithelium forming pseudomembrane Ulcer: Sore characterised by loss of epithelium yielding a punched out area. Traumatic ulcers, aphthous stomatitis, cancer and tuberculosis Fissure: Narrow linear crack of epidermis with an ulcer at its base. Fissured tongue Erosion: Partial loss of upper layers of epithelium. Toothbrush trauma, erosive lichen planus
Cyst: Cavity lined by epithelium containing fluid or cells. Gingival cyst Nodule: Localised elevated mass of tissue projecting from surface. Fibroma, mucocele Tumour: swelling of part of an organ. Inflammatory, Developmental or neoplastic. Carcinoma is a malignant tumour of epithelial cells Wheal: Pruritic reddened oedematous papule. Allergy Sinus/sinus tract: leading from underlying cavity cyst or abscess and opening onto surface
Scar: White depressed mark, line or area representing healing after injury. Gingivectomy, apicoectomy, deep inflammation, previous trauma
• In pathological conditions, the cytokeratin profile of epithelium has been seen to be altered.• Pancytokeratin antibodies are now in use to differentiate neoplasms.• Also helpful in determining the origin of cysts within jaws and to differentiate odontogenic cysts from non odontogenic cysts. (CK 13)
• Ten Cate’s Oral Histology: Development, Structure and function by Antonio Nanci. 6th edition• Oral Anatomy Histology and Embryologyby Berkovitz, Holland, Moxham . 3rd edition• Essentials of Oral Histology and Embryology by James K. Avery• Carranza;s Clinical Periodontology by Newman, Takei, Carranza. 9th edition• Dentistry for Child and Adolescent by Mc Donald, Avery, Dean . 8th edition• Orban’s Oral Histology and Embryology . 10th edition