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)