oral mucosa
TRANSCRIPT
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