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Brief histology of oral mucous membrane
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Oral Mucous Membrane
1.Oral Mucosa
The moist lining of the oral cavity is called Oral Mucosa or Oral Mucous Membrane
The function of oral mucosa is protection, sensation and secretion
It is continuous with the skin outside the oral cavity and differs from it in appearance and structure
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Dr.S
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Oral Mucous Membrane
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Oral Mucous Membrane
Epithelium
Lamina Propria
Submucosa
PeriosteumBone
Oral Epithelium
Oral epithelium forms the surface of the oral mucosa that forms a barrier between the oral environment and the deeper tissues
It is derived from the embryonic ectoderm
It is stratified squamous epithelium and may or may not be keratinized
Beneath the epithelium lies the connective tissue
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Oral Epithelium -Keratinized
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Keratinized oral epithelium
Most of the oral mucosal surface is lined by nonkeratinized stratified squamous epithelium except gingiva, hard palate and dorsal surface of the tongue where the epithelium is keratinized
The keratinized cells have no nuclei and the cytoplasm is displaced by large numbers of keratin filaments
Keratinized epithelium is associated with masticatory function and have four layers of cells
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The four layers are:
1.Stratum Basale
2.Stratum Spinosum
3.Stratum Granulosum
4.Stratum Corneum
Cellular layers of oral epithelium - Keratinized
1. Stratum Basale
The cells of the stratum basale are cuboidal or low columnar and form a single layer resting on the basal lamina
The basal lamina is at the interface of the epithelium and lamina propria
Epithelial cells of the oral mucosa are in a constant state of renewal
The basal cells show the maximum mitotic activity
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2. Stratum Spinosum
Stratum spinosum is usually several cells thick
They shaped like polyhedron with short cytoplasmic processes
The stratum basale and the first layers of stratum spinosum are referred to as stratum germinativum because these cells give rise to new epithelial cells
3. Stratum Granulosum
Cells of stratum granulosum are flat and are found in layers of three to five cells thick
This layer is prominent in keratinized epithelium (and absent in nonkeratinized epithelium)
These cells have keratohyaline granules in their cytoplasm
Keratohyaline granules help to form the matrix of the keratin fibres found in the superficial layer
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4. Stratum Corneum
Cells of stratum corneum are flat, devoid of nuclei and full of keratin filament surrounded by a matrix
These cells are continuously being sloughed and are replaced by epithelial cells that migrate from the underlying layers
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Nonkeratinized oral epithelium
Nonkeratinized epithelial cells in the superfecial layers do not have keratin filaments in the cytoplasm
The surface cells also have nuclei
The stratum corneum and stratum granulosum layers are absent
This epithelium is associated with lining of the oral cavity
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Connective tissue
Connective tissue can be differentiated as Lamina Propria and Submucosa
Lamina propria
Lamina propria is the connective tissue layer immediately below the epithelium
It can be divided into papillary layer and the reticular layer
Papillary layer forms finger like projections of connective tissue that extend deep in the epithelial layers
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Papillary layer is prominent in masticatory mucosa and reticular layer is prominent in lining mucosa
Lamina prorpria consists of blood vessels and cells like fibroblasts, cells of blood vessels and lymphatics and nerves
Epithelium is avascular, hence its metabolic needs come via the vessels of the lamina propria
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Submucosa
Submucosa lies below the lamina propria and serves as an attachment between lamina propria and bone or skeletal muscle
It is found in the cheeks, lips and parts of the palate
It consists of large blood vessels, nerves and lymphatics and its functions are nutrition and defense
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2. Functional types of Oral Mucosa
Lining mucosa and Masticatory mucosa
Lining mucosa
Lining mucosa covers all soft tissue of the oral cavity except the gingiva, hard palate and the dorsal surface of the tongue
Lip
Lip is covered by lining mucosa
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Lip with skin on outer surface and lining mucosa on inner surface
Vermilion border
The junction between the skin and mucous membrane is known as the vermilion border
Here the epithelium is thin therefore, the red blood cells in the capillaries show through contributing to the vermilion colour
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Vermelion Zone
Ventral surface of the tongue
The lining mucosa here contains both lamina propria and submucosa
The submucosa merges with the muscle bundles of the ventral surface of the tongue D
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Ventral surface of tongue
Cheek
In the cheek the underlying submucosa contains fat cells and small mixed salivary glands
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Cheek
Floor of the mouth
The mucous membrane of the floor of the mouth is thin and loosely attached to the underlying structures
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Floor of the mouth
Masticatory mucosa
Masticatory mucosa covers the gingiva and hard palate
In edentulous mouth, masticatory mucosa covers the chewing surface of the dental arches
Gingiva
Gingiva has keratinized or parakeratinzed epithelium with no submucosal layer
It develops from the union of oral epithelium and reduced enamel epithelium of the developing tooth
Gingiva can be classified as free gingiva, attached gingiva and interdental papilla
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Normal Gingiva
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Development of gingiva from oral epithelium and reduced enamel epithelium
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Anatomy of gingiva
Free gingiva (or marginal gingiva)
It is that part of the oral mucosa that surrounds the necks of the teeth and forms the free margin of the gingival tissue
It is differentiated apically from the attached gingival by the free gingival groove
The inner side of it forms the gingival sulcus
The free gingival mucosa is composed of stratified squamous epithelium that may be keratinized, parakeratinzed or sometimes nonkeratinized
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Free gingiva
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Alveolar Mucosa (Arrows - Interdental Papillae)
Attached gingiva
The attached gingiva lies between the free gingival groove and the alveolar mucosa
The junction of the attached gingiva and the alveolar mucosa is called mucogingival junction
In healthy mouth attached gingiva shows stippling (orange-peel appearance) which is a characteristic of this type of mucosa
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Histology of gingiva
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Mucogingival junction (arrows)
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Alveolar Mucosa
Interdental papilla
Interdental papillae are those parts of gingival tissue that appear in-between teeth apical to the contact points
Interdental grooves extend vertically between the interdental papilla corresponding to the depressions between the roots
Confirming to the shape of the interproximal contact area is a valley like depression in the interdental papilla called Col.
This depression lies in the facial and lingual plane
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Interdental Papilla (arrow)
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Diagram of positional relation of col in health and disease for canine, premolar and molar
Col accentuated during inflammation (arrows)
Junctional epithelium
Junctional epithelium forms the seal of the gingival epithelium and the tooth
It forms the floor of the gingival sulcus and extends apically to the enamel of the tooth
Disturbances of epithelial attachment results in deepening of the sulcus which is a sign of gingival/periodontal disease
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Histology of gingiva
Hard palate
The surface of the hard palate that is visible in the mouth is covered by masticatory mucosa
The lateral regions of the posterior part contains palatine glands
These glands are purely mucous glands
The midline of the hard palate is called median raphe where there is no submucosa
A series of folds appear in the anterior part of the palate called rugae
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Hard Palate and Soft Palate
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Palatal rugae (arrow)
3 Mucosa of the Tongue
Specialized mucosa covers the dorsal surface of the body of the tongue
The connective tissue binds the epithelium to the underlying skeletal muscle
The epithelium is modified, keratinized, stratified covered with papillae, which can be seen by naked eye
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The different papillae found on the dorsal surface of the tongue are:
1.Filliform papillae
2.Funginform papillae
3.Circumvallate papillae
4.Foliate papillae
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Dorsum of Tongue
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Cross section of tongue
1. Filliform papillae
Filliform papillae are pointed extensions of the keratinized epithelial cells
They are the most numerous papillae of the tongue
They are not associated with taste buds
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Scanning electron micrograph of Filliform papillae(arrow)
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Filliform Papillae
2. Fungiform papillae
Fungiform papillae are fewer than the filliform papillae and are scattered over the dorsal surface of the tongue
They are rounded elevations above the surface of the tongue
They have taste buds on their superior surfaces
The surface of fungiform papillae is not keratinized
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Scanning electron micrograph of Fungiform papillae (arrow) surrounded by Filliform papillae
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Fungiform Papillae
3. Circumvallate papillae
The circumvallate papillae are located at the junction of the anterior two thirds (body) and posterior one thirds (base) of the tongue
There are eight to twelve in number and are bigger than fungiform papillae
Circumvallate papillae are lined with taste buds and also openings of serous glands
The secretion from the serous glands washes away food for renewal of taste
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Circumvallate Papilla and Taste buds (arrows)
4. Foliate papillae
Foliate papillae are located in the furrows along the posterior sides of the tongue
They may be lined with taste buds
They are not prominent in human beings
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