Oral Mucous Membrane

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Babylon University College of Dentistry Babylon University College of Dentistry

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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

Oral Mucous Membrane

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

Oral Epithelium -Keratinized

CELL LAYERS OF ORTHOKERATINISED EPITHELIUM

KERATINIZED EPITHELIUM

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

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

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

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

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

NON KERATINIZED EPITHELIUM

LAMINA PROPORIA

LAMINA PROPORIA

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

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

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

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

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

Vermelion Zone

VERMILLION BORDER OF LIP

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

Ventral surface of tongue

HARD PALATE

SOFT PALATE

Cheek

In the cheek the underlying submucosa contains fat cells and small mixed salivary glands

Cheek

Floor of the mouth

The mucous membrane of the floor of the mouth is thin and loosely attached to the underlying structures

Floor of the mouth

Masticatory mucosa

Masticatory mucosa covers the gingiva and hard palateIn edentulous mouth, masticatory mucosa covers the chewing surface of the dental arches

Gingiva

Gingiva has keratinized or parakeratinzed epithelium with no submucosal layerIt develops from the union of oral epithelium and reduced enamel epithelium of the developing toothGingiva can be classified as free gingiva, attached gingiva and interdental papilla

Normal Gingiva

Development of gingiva from oral epithelium and reduced enamel epithelium

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

Free gingiva

A- gingiva

B- sulcular epithelium

C- junctional epithelium

D- lamina propria (connective tissue)

E- alveolar process

F- PDL

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

Histology of gingiva

Mucogingival junction (arrows)

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

Interdental Papilla (arrow)

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

Histology of gingiva

GINGIVA

TYPES OF EPIFHELIUM:

Oral or outer epithelium sulcular epitheliumJunctional epithelium

Sulcular epithelium

Junction epithelium

Oral epithelium

HISTOLOGY OF GINGIVA

GINGIVAL EPITHELIUM

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 glandsThese 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

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

The different papillae found on the dorsal surface of the tongue are:1.Filliform papillae

2.Funginform papillae

3.Circumvallate papillae

4.Foliate papillae

Dorsum of Tongue

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

Scanning electron micrograph of Filliform papillae(arrow)

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

Scanning electron micrograph of Fungiform papillae (arrow) surrounded by Filliform papillae

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

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

TONGUE

PAPILLAE OF TONGUE

FILIFORM PAPILLAE

FUNGIFORM & CIRCUMVALLATE

TASTE BUDS

TASTE BUDS

TASTE PORES

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