Post on 07-Aug-2015
ORAL MUCOUS MEMBRANE
PRESENTED BY :- Dr. Aditya Shinde GUIDED BY :- Dr. Lalitagauri Mandke
Framework of the topic
DEFINITION
FUNCTIONS
ORGANIZATION
CLINICAL FEATURES
ORAL EPITHELIUM
BLOOD SUPPLY AND NERVE SUPPLY
Oral Cavity (Mouth) Extends from the lips to
the oropharyngeal isthmus
The oropharyngeal isthmus: Is the junction of mouth and pharynx.
Is bounded:
1- Above by the soft palate and the palatoglossal folds 2- Below by the dorsum of the tongue Subdivided into Vestibule
& Oral cavity proper
Vestibule Slit like space between
the cheeks and the gums Communicates with the
exterior through the oral fissure
When the jaws are closed, communicates with the oral cavity proper behind the 3rd molar tooth on each side
Superiorly and inferiorly limited by the reflection of mucous membrane from lips and cheek onto the gums
Vestibule cont’d
The lateral wall of the vestibule is formed by the cheek
The cheek is composed of Buccinators muscle, covered laterally by the skin & medially by the mucous membrane
A small papilla on the mucosa opposite the upper 2nd molar tooth marks the opening of the duct of the parotid gland
Oral Cavity Proper
It is the cavity within the alveolar margins of the maxillae and the mandible
Its Roof is formed by the hard palate anteriorly and the soft palate posteriorly
Its Floor is formed by the mylohyoid muscle. The anterior 2/3rd of the tongue lies on the floor.
hard
soft palate
mylohyoid
ORAL MUCOSA
Mucous Membrane: Moist lining of the gastrointestinal tract, nasal passages and other body cavities that communicate with the exterior
In the oral cavity the lining is called as Oral Mucous Membrane or Oral Mucosa
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, etching, gagging and salivating
3. Secretion: Salivary secretion
4. Thermal regulation: Important in dogs not in humans
CLASSIFICATION OF ORAL MUCOSA: FUNCTION
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MASTICATORY MUCOSA
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MASTICATORY MUCOSA
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LINING MUCOSA
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SPECIALIZED MUCOSA
CLINICAL FEATURES OF ORAL MUCOSA
1. Separated from the skin by vermillion zone of the lips which is more deeply colored 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 oral tissues appear red rather than the normal pale pink
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NORMAL VS INFLAMED TISSUES
LINEA ALBA
The linea alba (Latin for white line)to describe a horizontal streak on the inner surface of the cheek level with the biting plane.
It usually extends from the commissure to the posterior teeth and can extend to the inner lip mucosa and corners of the mouth.
most likely associated with pressure, frictional irritation, or sucking trauma from the facial surfaces of the teeth.
STRUCTURE OF ORAL MUCOSA
1. Overlying oral epithelium
2. Underlying connective tissue (lamina propria and sub mucosa)
In skin called epidermis and dermis
The oral mucosa is of stratified squamous type.
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The oral epithelium is keratinized or non-keratinized stratified squamous epithelium
The interface between epithelium and connective tissue is comprised of aStructure less layer called basement membrane
This interface is irregular and is composed of downward projections of epitheliumcalled 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
Junction between oral epithelium and lamina propria is more obvious than that betweenlamina propria and sub mucosa
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 sub mucosa 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
BASEMENT MEMBRANE Interface between
connective tissue and epithelium appears thick and it includes reticular fibres.
1-4 micrometre wide and cell free.
Ultra structurally , basement membrane is called Basal Lamina.
Basal lamina is made up of clear zone called Lamina Lucida just below the epithelial cells.
A dark zone beyond lamina lucida adjacent to the connective tissue is called Lamina Densa.
ULTRASTRUCTURE OF BASAL LAMINA
LAMINA PROPRIASuperficial papillary layer (associated with rete ridges) and deeper reticular layer(between papillary layer and deeper structures)
Reticular refers to the netlike arrangement of collagen fibers (nothing to do with reticulin fibers)
Papillary layer has thin and loose collagen fibers with many capillary loopsReticular layer has collagen fibers arranged in thick bundles that are parallel to surface
Lamina propria also contains various cells, blood vessels, nerves and fibers(collagen and elastic) embedded in an amorphous ground substance
SUBMUCOSA
Consists of connective tissue of varying thickness and density.
It attaches mucous membrane to underlying structures.
Glands , nerves , blood vessels and also adipose tissue are present.
STRATUM BASALE
Basal layer is made up of single layer of cuboidal cells that undergo mitosis.
New cells are generated in basal layer. The basal cell and parabasal spinous
cells are called Stratum Germinativum , but only basal cells divide.
Basal cells are made up of two populations: serrated and heavily packed with tonofilaments.
And the other is non serrated and is composed of slowly serrated stem cells.
Specialized structures called Hemi desmosomes which abut on the basal lamina are found on the basal surfaces.
The lateral border of adjacent basal cells are closely apposed and connected of Desmosomes.
STRATUM SPINOSUM
Spinous cells are irregularly polyhedral and larger than basal cells.
Cells are joined by intercellular bridges.
electron microscopy shows that the intercellular bridges are desmosomes and tonofibrils are bundles of tonofilaments.
The tonofilament network and desmosomes appear to make up tensile supporting system for the epithelium.
The spiny appearance of spinous layer is due to the shrinkage of cells during tissue preparation causing them to separate at points where the desmosomes do not attach them.
The spinous layer resemble a Cocklebur or sticker that has each spine ending at a desmosome.
STRATUM GRANULOSUM This layer contains flatter and
wider cells. This layer is named for basophilic
keratohyalin granule layer that it contains.
Nuclei shows degeneration and pyknosis.
The lamellar granule , a small organelle also known as keratinosome , Odland body or membrane coating granule , forms in upper spinous and granular layer.
In non keratinizing oral epithelium a small granule forms.
These granules are elongated ,and lamellar in keratinized & circular & amorphous in nonkeratinized epithelium.
STRATUM CORNEUM
Other name is cornified layer and horny layer.
Is made up of keratinized squamae which are larger and flatter than the granular cells.
All nuclei and ribosomes and mitochondria have disappeared.
The cells are densely packed with filaments in this nonfibrous interfilamentous matrix protein , filaggrin.
NONKERATINIZED EPITHELIUM They do not produce a
cornified surface layer.The cells in
nonkeratinizing epithelium are called as basal , intermediate, and superficial layer. ( stratum basale , stratum intermediate, stratum superficiale.)
The cells of stratum intermedium are larger than cells of larger than cells of stratum spinosum.
There is no stratum granulosum / nor there is stratum corneum.
NON-KERATINOCYTES IN ORAL EPITHELIUM
Constitute about 10% of epithelial cell population. Three major cells which are all clear cells with a halo around their nuclei.
1. Langerhans cells: found on stratum spinosum (suprabasal) and function inantigen trapping and processing. Dendritic cells. No desmosomes or tonofilaments.
2. Merkel cell: Located in basal cell layer (mostly in gingiva). Function as touchreceptors. Nondendritic. Sparse desmosomes and tonofilaments.
3. Melanocytes: Found in basal cells. Melanin-producing cells (mostly in gingiva).Dendritic. Presence of melanin granules (melanosome).
4. Lymphocytes and leukocytes: Inflammatory cells that are not clear cells.Associated with inflammatory response in oral mucosa
Epidermal/epithelial cells that secrete keratin
Shows intermediate filament protein
Undergoes: cell division, maturation and finally desquamate.
Increase in volume: from basal to superficial.
Function : The primary function of keratinocytes is the formation of a barrier against environmental damage such as pathogens bacteria fungi viruses heat UV radiation and water loss
KERATINOCYTES
MELANOCYTES
Melanocytes are melanin-producing cells located in the bottom layer (the stratum basale).
embryological neural crest and migrate into epithelium
establishes contact through dendritic processes
appear clear in H and E stains, hence called as clear cells or dendritic cells.
Function: Melanin production
LANGERHANS CELLS
Langerhans cells are dendritic cells (antigen-presenting immune cells) of the skin and mucosa, and contain large granules called Birbeck granules.
Hematopoietic in origin. Free of melanin, do not
give dopa reaction. presents antigen to T cells.Function: Contact hypersensitivityAnti tumour immunityGraft rejection
Merkel cells are found in the stratum basale.
Specialized neural pressure- sensitive receptor cell.
Commonly seen in masticatory mucosa.
Non dendriticMigrate from the neural
crest.
MERKELS CELLS
JUNCTION BETWEEN EPITHELIUM & LAMINA PROPRIA
CELL TYPES IN THE LAMINA PROPRIA OF ORAL MUCOSA
FIBRES AND GROUND SUBSTANCES
The intercellular matrix of the lamina propria consists of 2 major types of fibres i.e. collagen and elastin.
Together with fibronectin embedded in ground substance composed of glycosaminoglycan's and serum derived proteins.
Collagen: lamina propria is type I and type III , IV and VII in basal lamina. Type V in inflamed tissue.
Elastic fibres: consists of 2 protein components Ground substance: it consists of protein-carbohydrate
complexes permeated by tissue fluid.Chemically , these complexes can be sub divided into: proteoglycans and glycoproteins.
BLOOD SUPPLY AND NERVE SUPPLY
Blood supply of gingiva is derived chiefly from the branches of alveolar arteries that pass upward through interdental septa.
Gingiva is well innervated . Different types of nerve endings can be observed , such as the Meissner or Krause corpuscles , end bulbs , loops or fine fibres that enter epithelium as “ultratterminal” fibres.
Blood supply to the gingiva: Derived from periosteal vessels in the periosteum of the alveolar process
Blood supply to the dentogingival junction: Continuation of interalveolar arteries
Nerve supply to the gingiva: terminal branches of periodontal nerve fibers and by branches of the infraorbital and palatine, or lingual, mental, and buccal nerves
Components of Oral Epithelium
LINING MUCOSA:
Stratum Basale: Basal cell layer comprised of cuboidal cells. Progenitor cells that divide and provide new cells by mitotic division that migrate to the surface to replace cells that are shed.
Stratum Spinosum (or intermedium): Cells are oval and represent bulk of the epithelium. Stratum Superficiale: Cells are flat and contain small oval nuclei that are continuously shed.
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JUNCTIONAL EPITHELIUM
The epithelium that is attached to the tooth (enamel or sometimes cementum) surfacecontinuous with sulcular epithelium
Derived from reduced enamel epithelium of the tooth germ
Junctional epithelium consists of flat cells aligned parallel to the tooth surfaceincreasing in thickness from the apex to the crown
Attached to enamel by internal basal lamina and to the connective tissue by externalbasal lamina. Hemidesmosomes are present in both basal laminas.
EPITHELIAL CELL TURNOVER IN GINGIVASimilar to all other epithelia, the deepercells adjacent to the connective tissueundergo cell division to replenish thoselost at the surfaceHigh rate of cell divisionMigrate about 2 to 3 cell layers from thetooth surface and then join a main migratoryroute in a coronal direction, parallel to toothsurface, to be desquamated into thegingival sulcus.Key point: Junctional epithelium readilyregenerates from the sulcular epitheliumor oral epithelium if it is damaged or surgically excised Connective tissue normally contains plenty of neutrophils which is differentthan the normal oral mucosa
DENTOGINGIVAL FIBRES
DENTOPERIOSTEAL FIBRES
ALVEOGINGIVAL FIBRES
CIRCULAR AND SEMICIRCULAR FIBRES
TRANSSEPTAL FIBRES
TRANSGINGIVAL AND INTERGINGIVAL FIBRES
INTERPAPILLARY FIBRES
PERIOSTEOGINGIVAL FIBRES AND INTERCIRCULAR FIBRES
REFERENCE :-
TEN CATE’S – ORAL HISTOLOGY , DEVELOPMENT STRUCTURE AND
FUNCTION
(7TH EDITION)
ORBAN’S ORAL HISTOLOGY AND EMBRYOLOGY
( 11TH EDITION)