oral mucosa 2020 part 1
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Oral Mucosa
Part 1
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Oral Mucosa
Mucous Membrane: Moist lining of the gastrointestinal tract, nasal passages andother body cavities that communicate with the exterior
In the oral cavity the lining is called as oral mucous membrane or oral mucosaThe oral mucosa begins at the junction of the vermillion and labial mucosa
Lips mark the entrance into the oral cavityExternal or “dry” areaVermillion between the external and internalInner aspect of the lip
Oral Mucosa
• Posterior aspect– Palatopharyngeal folds (opening of the
oropharynx)– Palatoglossal folds
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Functions of the Oral Mucosa
1. Protection: Barrier for mechanical trauma and microbiological insults
2. Sensation: Temperature (heat and cold), touch, pain, taste buds, thirst;reflexes such as swallowing, retching, gagging and salivating
3. Secretion: Salivary secretion
4. Thermal regulation: Important in dogs not in humans; panting dogs
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Organization of the Oral Mucosa
3 types according to FUNCTION:
1. Masticatory Mucosa: 25% of total mucosa. Gingiva (free, attachedand interdental) and hard palate. Primary mucosa to be in contact with foodduring mastication. MASTICATORY MUCOSA IS USUALLY KERATINIZED.
2. Lining Mucosa: 60% of total mucosa. Covers the floor of mouth, ventral(underside) tongue, alveolar mucosa, cheeks, lips and soft palate.Does not function in mastication and therefore has minimal attrition.Non-keratinized; soft and pliable.
3. Specialized Mucosa: 15% of total mucosa. Covers dorsal tongue andcomposed of cornified epithelial papillae.
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Masticatory Mucosa
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Masticatory Mucosa
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Lining Mucosa
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Specialized Mucosa
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General Features of Oral Mucosa
1. Separated from the skin by vermillion zone of the lips which is more deeplycolored than rest of the oral mucosa
2. Factors affecting color of the oral mucosa:a. Concentration and state of dilation of the blood vessels in
underlying connective tissueb. Thickness of the epitheliumc. Degree of keratinizationd. Amount of melanin pigmentation
Clinically, color of oral mucosa is very important. For example, inflamed oraltissues appear red rather than the normal pale pink
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How is the oral mucosa different from skin?
1. Color
2. Moist surface
3. Absence of adnexal skin structures such as hair follicles, sweat glandsand sebaceous glands (exception in Fordyce’s disease)
Fordyce’s disease: Sebaceous glands in oral cavity predominantly in upper lip, buccal mucosa and alveolar mucosa
4. Presence of minor salivary glands in oral mucosa
5. Texture of surface: Oral mucosa is smoother than the skin (few exceptionslike dorsal tongue – due to papillae; hard palate – rugae; gingiva – stippling)
6. Firmness: Oral mucosa varies in its firmness. For example buccal mucosaand lips are loose and pliable whereas the gingiva and hard palate are firmso critical clinically while giving injections
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Skin Oral Mucosa-Cheek
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Fordyce’s Spots
• Pale yellow spots
• Normal variation
• Lips, buccal mucosa, alveolarmucosa and tonsillar pillar
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Structure of Oral Mucosa1. Overlying oral epithelium2. Underlying connective tissue (lamina propria and submucosa)
In skin called epidermis and dermis
Rete ridges/pegs
Connective tissue papilla
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The oral epithelium is keratinized or non-keratinized stratified squamous epithelium
The interface between epithelium and connective tissue is called basement membrane
Downward projections of epithelium called rete ridges or rete pegs, and upward projection of connective tissue termed as connective tissue papillae
A: EpitheliumB: Connective tissueC: Salivary gland
A: Startum basaleB: Startum spinosumC: Startum superficiale
http://dentistry.ouhsc.edu/intranet-WEB/Courses/CELL8002/Home.html
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Junction between oral epithelium and lamina propria is more obvious than that betweenlamina propria and submucosa
No muscularis mucosae layer seen in oral mucosa
Loose fat and glandular tissue with blood vessels and nerves seen underneath oral mucosafrom underneath bone or muscle layer - this layer is termed SUBMUCOSA – provides flexibility
In gingiva and hard palate, no submucosa is seen and the lamina propria is directlyattached to the periosteum of the underlying bone which provides firm, inelastic attachment –this is called ORAL MUCOPERIOSTEUM
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Connective tissue in oral cavity is comprised of salivary glands, sebaceous glands(Fordyce’s disease) and lymphoid tissue (tonsillar tissue)
Salivary glands Sebaceous glands Lymphoid tissue (tonsil)
www.usc.edu/hsc/dental/opfs/QL/09tn.html
http://www.usc.edu/hsc/dental/ohisto/index.html
High Power view of sebaceous glands
http://dentistry.ouhsc.edu/intranet-WEB/Courses/CELL8002/Home.html
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Oral Epithelium
Progenitor population: Divide and provide new cells (Proliferation)Maturing population: Undergo differentiation (maturation)
Estimated time necessary to replace all the cells in the epithelium: turnover time
Skin: 52 to 75 daysGut: 4 to 14 daysGingiva: 41 to 57 daysCheek: 25 days
Nonkeratinized epithelium turns over faster than keratininzed epithelium
Clinical correlation: Oral ulcers during cancer chemotherapeutic treatment
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Types of Oral EpitheliumOrthokeratinized stratified
squamous epitheliumParakeratinized stratified
squamous epitheliumNonkeratinized stratified
squamous epithelium
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Components of Oral Epithelium
Lining Mucosa:
Stratum Basale: Basal cell layer comprised of cuboidal cells. Progenitorcells that divide and provide new cells by mitotic division that migrate to thesurface to replace cells that are shed.
Stratum Spinosum (or intermedium): Cells are oval and represent bulkof the epithelium.
Stratum Superficiale: Cells are flat and contain small oval nuclei that arecontinuously shed.
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Histology of Lip
A: SkinB: Vermillion zoneC: Oral (labial) mucosaD: Minor salivary glands
Skin: keratinized stratified squamousepithelium with adnexal skin structures
Oral Mucosa: Moist-surface, covered bynonkeratinized stratified squamous epitheliumassociated with small round seromucousglands of the lamina propria. In thesubmucosa fibers of orbicularis oris muscle isnoted.
Vermillion zone: Very thin keratinizedepithelium that contains no adnexal skinstructures (can contain sebaceous glands)
What gives the vermillion zone the red color?1. Epithelium is thin2. Epithelium contains eleidin, which is
transparent3. Blood vessels are present near the surfaceEleidin is a semi-fluid clear substance presentin the stratum lucidum of the skin epithelium
http://dentistry.ouhsc.edu/intranet-WEB/Courses/CELL8002/Home.html
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Skin of the Lip Vermillion Zone and Labial Mucosa
A: Sweat glandsB: Sebaceous glandsC: Hair follicles
A: Vermillion zoneB: Labial mucosaC: Orbicularis oris muscle
http://dentistry.ouhsc.edu/intranet-WEB/Courses/CELL8002/Home.html
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Soft palate
A: Hard PalateB; Soft palateC: Nasal cavity
1. Nonkeratinized2. Highly vascularized so more pink
than hard palate2. Lamina propria and submucosa
present (unlike hard palate whenonly lamina propria is noted –mucoperiosteum)
3. Submucosa contains salivaryglands and muscle soft palatehttp://dentistry.ouhsc.edu/intranet-WEB/Courses/CELL8002/Home.html
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Cheeks (Buccal Mucosa)
Similar to lips and soft palate
Nonkeratinized stratified squamous epithelium, lamina propria and submucosa
Submucosa of cheeks contain fat cells along with lobules of minor salivaryglands and muscle fibers
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Ventral surface of tongue
Nonkeratinized stratified squamousepithelium, lamina propria andsubmucosa
Extremely dense muscle fibersinterlacing connective tissue fibersin submucosa
Floor of mouth
Nonkeratinized stratified squamousepithelium, lamina propria and submucosa
Epithelium is loosely attached tolamina propria
No muscle
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Masticatory Mucosa
Epithelium that covers gingiva and hard palate
Mucosa is thicker than nonkeratinized because of the keratin layer
Stratum basaleStartum spinosum
Stratum granulosum: Cells contain keratohyaline granules
Stratum corneum: Contains thin, flat and nonnucleated cells which are filled withkeratin. In contrast to the hard keratin seen in nails and hair, keratin overlyingnormal masticatory oral mucosa is soft. Keratin is tough, nonliving material thatis resistant to friction and impervious to bacterial invasion
Same as nonkeratinized epithelium
Miller SE. Histology for Pathologists. 3rd edition. LWW. 2007
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Types of Keratinized Epithelium
The superficial cells are dead but retain the nucleus in parakeratinized epitheliumbut the nuclei are lost in orthokeratinized epithelium
The rete pegs are long and slender in keratinized epithelium
Mucoperiosteumhttp://dentistry.ouhsc.edu/intranet-WEB/Courses/CELL8002/Home.html
Miller SE. Histology for Pathologists. 3rd edition. LWW. 2007