Oral Mucosa

ORAL MUCOSA

• It is a mucous membrane epithelium of the mouth.

• Divided into 3 types:• Lining mucosa – covers the floor of the

mouth, the cheeks, lips and soft palate• Masticatory mucosa – covers the hard palate

and alveolar ridges• Specialized mucosa – covers the surface of

tongue

The mucosa has lamina propria, the connective tissue just below the epithelium

Lamina propria is composed of papillary and reticular layers

In the papillary layer, the connective tissue extends into pockets in the epithelium.

This increases the surface of the epithelium for contact with vascular supply and nerves

The reticular layer contains the deeper plexus of vessels and nerves

Below the lamina propria is the submucosa

Lining mucosaIts soft, pliable and nonkeratinizedCovers the lips, cheeks, soft palate, floor of

mouth and ventral surface of the tongueMucosa is composed of thin layer of

epithelium and lamina propriaFrom bottom to top the epithelium has this

layers: stratum basale, stratum intermedium or spinosum and stratum superficiale

Stratum basale – cells are cuboidalStratum intermedium – cells are oval and

somewhat flattenedStratum superficiale – cells are flanned with

small oval nuclei

The lining is similar to that of the pharynx

Associated with small, round seromucous glands of the lamina propria

Submucosa has fibers of M. Orbicularis oris The mucosa is distinguished by a red border

known as vermillion borderVermillion border is the junction between the

oral mucosa and the skin of the lips, becoming modified into keratinized epithelium

Why is the vermilion border red in colour?The epithelium is thinThe epithelium contains eleidin, which is

transparentThe blood vessels are near the surface of the

papillary layer, revealing the red blood cell colour

The skin of the lip has hair follicles and associated sebaceous glands, erector pili muscles and sweat glands

Sometimes the sebaceous glands may be seen at the angle of the mouth without associated hair follicles. The glands are termed Fordyce’s spots

Soft palateMucosa is more pink than that of the hard

palate. Why pink? Because the lamina propria

contains many small blood vesselsThe submucosa contains muscles of the soft

palate and minor salivary (mucous) glands

Cheeks CheeksThe submucosa contains fat cells and

seromucous glands located within and between the muscle fibers

Ventral surface of the tongueIn the submucosa, muscle fibers are located

under the surface of the tongue

The entire are exhibits dense, interlaced muscle and connective tissue fibers

Limits of the submucosa are not distinct because the submucosa continues with the deep muscles of the tongue along with the CT fibers

The mucosa is well vascularized and is used for drug delivery in patients who suffer from cardiovascular and other systemic disease

Floor of the mouthThe epithelium appear loosely attached to the

lamina propria in contrast to the adjacent undersurface of the tongue mucosa which is firmly attached

The area contains minor salivary glands and right and left major mucous glands, sublingual glands

Masticatory mucosaIt’s a thick keratinized epithelium that

renders the epithelium resistance to attritionCovers gingiva and hard palateLayers of the epithelium from bottom to top:

stratum basale, stratum intermedium, stratum granulosum and stratum corneum

Stratum basal – cells are cuboidal/columnar with irregularly oval nuclei and numerous mitotic figures

Cont….The layer exhibit numerous mitotic figures as

they undergo constant cell divisionThe cells gradually migrate to the surface of

the mucosaBasal cells are attached to the basal lamina

(membrane that separate epithelium and connective tissue) by a minute disks termed hemidesmosomes

These thickenings of the cell membrane are supported by filaments from within the cells,

Also by anchoring fibrils that attach the basal lamina and the epithelial cells to the collagen fibers of the lamina propria

Stratum spinosum – several cells thick, cells are oval polygonal in shape

Stratum granulosum – contain many keratohyalin granules

Stratum corneum – cells are thin, flattened and nonnucleated. The cells contain soft keratin

Keratin is tough, nonliving material resistant to friction and impervious to bacterial invasion

The cells continually get lost and replaced by cells of the underlying layers = desquamation

Gingiva and epithelial attachment

Gingiva surrounds the necks of the teeth and extends apically to the mucogingival junction.

Divided into 3 zones: 1. Free or marginal zone – encloses the tooth

and defines the gingival sulcus2. Attached gingiva – portion of the

epithelium attached to the neck of the tooth by means of junctional epithelium

3. Interdental zone – area between the two adjacent teeth beneath their contact point

Free gingival groove is an indistinct groove that separates the free and attached gingivae

Attached gingiva is separated from the alveolar mucosa by mucogingival junction

Attached gingivae is stippled and the free gingiva has a smooth surface

Junctional epitheliumProvides attachment for the gingiva to the tooth

in the cervical areaForms the epithelium-lined floor of the sulcusThe cells have fewer desmosomes, indicating a

higher rate of turnover than occurs in the other gingival epithelial cells

Turnover time is approximately 6 daysStratum basale cells also contain

hemidesmosomes, the mechanism for attachment of cells to the salivary protein layer which covers the cervical area of enamel

Disturbance of this attachment to the tooth by infection, food impaction, calculus or other irritants results in a deepening of the gingival sulcus

Gingiva located between the teeth and extending high on the interproximal area of crowns on the labial and lingual surfaces is known as the interdental papilla

In the interproximal area, between the lingual and vestibular papilla, is a concave zone of the gingiva that follows the contour of each crown. The junctional epithelium of the zone is known as the col

The col is a thin nonkeratinized epithelium. Its more inclined in a peak between anterior teeth and more flattened or concave between the posterior teeth

When the interproximal gingiva is inflammed or hyperemic, the col is exaggerated and positioned higher on the neck of the tooth

Hard palateThe midline is known as median rapheOn each side of the median raphe are folds

known as rugaeAnterior lateral palate has fatty tissue in the

submucosaPosterior lateral area has mucous glandular

tissue Traction bands are bundles of collagen fibers

that insert into the papillary fibers of the lamina propria and extend into the bony palate

Traction bands are found in lamina propria of the rugae and between the lobules fatty tissue and glands

Helps in anchoring the palatal mucosa to the underlying bone

Hard palate assist in mastication

Specialized MucosaCovers the dorsum or superior surface of the

anterior 2/3 of the tongueHas four types of papille1.Filiform 2. Fungiform 3. Circumvallate 4. Foliate

Filiform papillaeMany, slender, threadlike keratinized extensions

of the surface epithelial cellsProjects 2-3 mm high from the surface of the

tongue

Covers the entire roughened surface of the tongueFunction: They facilitate mastication and

movement of the food on the surface of the tongue

Fungiform PapillaeFew in number, interspersed between the filiform

however numerous near the tip of the tonguePink or reddish, Mushroom-shaped with a cap

usually larger than the stalkTaste buds occasionaly found on superior surface

Circumvallate papilla10 – 14 in number, located along the V-shaped

sulcus between the body and base of the tongueThey are level with the surface of the tongue, each

surrounded by a grooveLarge to 3mm in diameterTaste buds line the walls of the papillaeDucts of Von Ebner’s glands opens into the

grooves Watery secretions washes out substances so that

new taste can be perceived

Foliate papillaeVertical grooves or furrows located on the

lateral posterior sides of the tongue4 to 11 in numberAlso contains serous glands underlying the

taste buds, which cleanse the trenches of the papillae

Taste budsSense organs containing the chemical sense of tasteMicroscopically visible, barrel-shaped bodies found

in the oral epitheliumGenerally associated with papillae of the

tongue(10000)Some distributed in the soft palate (2500), epiglottis

(900), larynx and pharynx (600), oropharynx (250)Taste cells are epithelial cells that are closely

associated with club-shaped sensory nerve endingsNerve arises from the chorda tympani

Four types of taste sensation can be detected: sweet, salty, sour and bitter

There is regional selectivity of taste in the mouth; maybe inpart caused by the origin of the nerve supply

Sweet – on the tip of tongueSalty – on the front sides of tongueSour – on the posterior sides of the tongueBitter – On the posterior centre of tongue and

soft palate

Nerves for taste buds of the anterior 2/3 pass to the chorda tympani branch of facial nerve

Those of posterior 1/3 pass to the glossopharyngeal nerve

Those from the epiglottis and larynx pass to the vagus nerve

Levels of sensitivity of the oral region

Sensation Greatest Moderate sensitivity sensitivity

Pain Lips, larynx Anterior tongue

base of tongue Heat Lips Tip of tongueCold Lips, Base of tongue posterior palate ventral tongueTouch Lips, tip of tongue Gingiva

EPITHELIAL NONKERATINOCYTELangerhans’ cellsFound in stratum spinosumResponsible for processing of antigenic

materialThe cell have processes but no desmosomes.

Unique racket-shaped organellesMerkel’s cell located in basal layer of gingival epithelium.

Associated with terminal axonFunction as touch receptors

MelanocyteMelanin producing cells located in the basal

layer of the gingival epitheliumLacks desmosomes, and tonofilaments and

are dendriticHas melanin granules in the cytoplasm

Changes with agingThinning of epitheliumLess moist mucosaAbility to repair is reduced, length of healing

time is increasedApical migration of gingivaCellular activity decreases, fibrosis increases