ORAL MUCOSA

ORAL MUCOSA

The oral cavity is lined with an uninterrupted mucous membrane, which is continuous with the skin near the vermilion border of the lips and with the pharyngeal mucosa in the region of the soft palate and anterior pillars of fauces.

The epithelium of the oral mucosa originates partly from the ECTODERM (lips, vestibule, gingiva, cheeks, palate, floor of the mouth), and pertly from the endoderm (tongue).

• free and attached gingiva and hard palate comes in primary contact with food during mastication and is keratinized.

MASTICATORY MUCOSA

• the lips cheeks, vestibule, floor of the mouth, interior surface of the tongue and soft palate. It does not function in mastication and therefore has little attrition. It is soft, pliable and non-keratinized.

LINING MUCOSA

• on the dorsal surface (dorsum) of the tongue. It is covered with cornified epithelial papillae

SPECIALIZED MUCOSA

FUNCTIONS OF THE ORAL

MUCOSA

• acts as major barrier to microorganismsProtection

• receptors that respond to temperature, touch, pain, taste; initiates reflexes such as swallowing, gagging and salivation

Sensation

• saliva, contributes to the maintenance of moist surface

Secretion

• thinnest epithelial regions, floor of the mouth, more permeable than other areas

Permeability and Absorption

• dogs, body heat is dissipated thru the oral mucosa by panting

Thermal Regulation

GENERALHISTOLOGIC

CHARACTERISTICSOF

ORALMUCOSA

Two main tissue components:

• stratified squamous epithelium

Oral epithelium

• undderlying connective tissue layer

Lamina Propia or Corium

The oral mucosa is attached to the underlying structures by a layer of loose fatty or granular connective tissue containing major blood vessels and nerves

• structureless layer about 1 – 2 micrometers thick; interface between epithelium and connective tissue

Basement

Membrane

• irregular and upward projections of connective tissue

Connective tissue papilla

• or rete pegs, epithelial ridges or pegs that interdigitate with the connective tissue papilla

Rete Ridges

HISTOLOGICCHARACTERIST

ICS OF THESURFACE

EPITHELIUM

Keratinization (types)• About 20-30% of the gingiva, the stratum corneum is

homogenous and made up of flat, closely packed keratinized cells without nuclei

Orthokeratinization

• Approximately 50-70% of the cases, the stratum corneum is homogeneous and consists of flat keratinized cells with pyknotic nuclei and remnants of cytoplasmic organelles

Parakeratinization

• - Least common type, approximately 7-10% of cases and is seen only in the region of the marginal gingiva. Stratum corneum is homogenous and consists of 2 cell types, which occasionally form 2 superimposed layers: the first type of cell is the same as cornified cell of a parakeratinized stratum corneum; the 2nd type is different from keratinized cells and seems to reach the stratum corneum and its surface without being transformed nto a keratinized cell.

Incomplete Keratinization

ORAL EPITHELIUMOral 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

Keratinized oral epitheliumMost 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 keratinizedThe 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

Layers of the Keratinized Surface Epithelium

1.Stratum

Basale2.Stratu

m Spinosu

m3.Stratum

Granulosum4.Stratum

Corneum

STRATUM BASALEThe 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

STRATUM SPINOSUM

Stratum spinosum is usually several cells thick

They are 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

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

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

Connective tissueConnective tissue can be differentiated as Lamina Propria and Submucosa

Lamina propria

• Lamina propria is the connective tissue layer immediately below the epithelium

Lamina propia can be divided into:1)papillary layer - prominent in masticatory mucosa2)reticular layer-prominent in lining mucosa• Lamina propria consists of blood vessels and cells

likefibroblasts, 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 of mucosa are nutrition and defensive.

Functional types of Oral Mucosa• Lining mucosa covers all soft

tissues of the oral cavity except the gingiva, hard palate and the dorsal surface of the tongue

A) Lining mucosa

LipLip is covered by lining mucosa

Lip with skin on outer surface and lining mucosa on inner surface

Vermilion borderThe junction between the skin and mucous membrane isknown as the vermilion border.Here the epithelium is thin therefore, the red blood cells in thecapillaries show through contributing to the vermilion colour

Ventral surface of the tongueThe lining mucosa here contains both lamina propria andsubmucosaThe submucosa merges with the muscle bundles of theventral surface of the tongue

CheekIn the cheek the underlying submucosa contains fat cells andsmall mixed salivary glands

Floor of the mouthThe mucous membrane of the floor of the mouth is thin andloosely attached to the underlying structures

• Masticatory mucosa covers the gingiva and hard palate.

• In edentulous mouth, masticatory mucosa covers the chewing surface of the dental arches.

B) Masticat

ory mucosa

Gingiva• Gingiva has keratinized or parakeratinzed

epithelium withno submucosal layer• It develops from the union of oral epithelium and

reducedenamel epithelium of the developing tooth

Hard palate• The surface of the hard palate that is visible in

the mouth iscovered by masticatory mucosa• The lateral regions of the posterior part

containspalatine 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 palatecalled rugae

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 papillae2.Funginform papillae3.Circumvallate papillae4.Foliate papillae

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)

2)Fungiform papillae• Fungiform papillae are fewer than the

filliform papillae and arescattered over the dorsal surface of the tongue• They are rounded elevations above the

surface of the tongue• They have taste buds on their superior

surfacesThe surface of fungiform papillae is not keratinized

3)Circumvallate papillae• The circumvallate papillae are located at

the junction of theanterior two thirds (body) and posterior one thirds (base) ofthe tongue• There are eight to twelve in number and

are bigger thanfungiform papillae• Circumvallate papillae are lined with taste

buds and alsoopenings of serous glands• The secretion from the serous glands

washes away food forrenewal of taste

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