ORAL MUCOSA

by

Dr.Carmina Romero Granado

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).

MASTICATORY MUCOSA – free and attached gingiva and hard palate comes in primary contact with food during mastication and is keratinized.LINING 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.SPECIALIZED MUCOSA – on the dorsal surface (dorsum) of the tongue. It is covered with cornified epithelial papillae.

Functions of the Oral Mucosa

Protection – acts as major barrier to microorganismsSensation – receptors that respond to temperature, touch, pain, taste; initiates reflexes such as swallowing, gagging and salivation Secretion – saliva, contributes to the maintenance of moist surfacePermeability and Absorption – thinnest epithelial regions, floor of the mouth, more permeable than other areasThermal Regulation – dogs, body heat is dissipated thru the oral mucosa by panting

General Histologic Characteristics of Oral Mucosa

Two main tissue components:Oral epithelium – stratified squamous epitheliumLamina Propia or Corium – undderlying connective tissue layer

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

Basement Membrane – structureless layer about 1 – 2 micrometers thick; interface between epithelium and connective tissueConnective tissue papilla - irregular and upward projections of connective tissue Rete Ridges – or rete pegs, epithelial ridges or pegs that interdigitate with the connective tissue papilla

BASEMENT LAMINACONNECTIVE TISSUE PAPILLA

RETE RIDGES

Histologic Characteristics of the Surface Epithelium

Keratinization (types)Orthokeratinization - About 20-30% of the gingiva, the stratum corneum is homogenous and made up of flat, closely packed keratinized cells without nuclei Parakeratinization - 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

Incomplete Keratinization - 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 into a keratinized cell.

Layers of the Keratinized Surface Epithelium

Stratum corneum dehydrated and flattened thus more resistant to mechanical damage and chemical solventsassume the form of hexagonal disks called squamesdo not contain any nuclei up to 20 layers of squames and is thicker than that of most of the skin except the soles and palms

Stratum Granulosum ( granular layer)

larger flattened cells containing small granules called keratohyalin granules

some regions of the masticatory oral epithelium (e.g. gingiva) it is difficult to see the granules under the light microscope

Stratum spinosum (Prickle-cell layer)several rows of larger elliptical or spherical cells

appearance of cells when prepared for histologic examination – shrink away from each other remaining in contact only at point known as intercellular bridges or desmosomes

Stratum Basale ( Basal layer)cuboidal to columnar cells adjacent to the basement membrane

Layers of Non-Keratinized Surface Epithelium

Stratum Basale

Cuboidal or columnar cells containing separate tonofilaments and other cell organelles

Site of most cell divisions

Stratum Intermedium

Slightly increase in cell size as well as accumulation of glycogen in cells of the surface layer

On rare occasion, keratohyalin granules can be seen

Stratum Superficiale ( Superficial layer)

Cells appear slightly flattened than in the preceding layers and contain dispersed tonofilaments and nuclei, the number of other cell organelles having diminished

Layers of Lamina Propia/Corium

Papillary layer or Connective tissue papilla

Indents and interdigitates with the epithelium (rete ridges/pegs)

May be short or absent in some mucosa

Reticular LayerConsists of densely arranged connective tissue fibers (reticular)

Subdivisions of the Oral Mucosa

Lining Mucosa

Lips

Lined by a moist, stratified squamous non-keratinized epitheliumNon-keratinized mucosa is distinguished by a red border known as vermilion borderThis area is at the junction between the oral mucosa and the skin of the lips, becoming modified into keratinized epihtelium

Three reasons why vermilion border is red:

Epithelium is thin

This epithelium contain eleidin, which is transparent

The blood vessels are near the surface of the papillary layer

Soft Palate

Stratified squamous non-keratinizing epithelium – highly vascularizedMore pink than the mucosa of the keratinized hard palate – lamina propia contains many small blood vesselsBeneath the CT of the lamina propia is the submucosa which contains muscles and mucous glands

Cheeks

Mucosa is same as the lips and soft palate, however, the submucosa contains fat cells and mixed glands (seromucous) located within and between the muscle fibers

The presence of these glands is a unique feature of the cheeks

Ventral Surface of the Tongue

Lining mucosa also contains lamina propia and submucosa

In the submucosa, muscle fibers are located under the surface of the tongue

The entire area exhibits dense, interlaced muscle and CT fibers

Floor of the Mouth

Non-keratinized mucous membrane

Covering appears loosely attached to the lamina propia in contrast to the mucosa of the ventral surface of the tongue which is firmly attached

Presence of minor salivary glands and right and left major mucous glands, the sublingual glands

Masticatory Mucosa

Gingiva or Marginal Epithelium

part of the oral mucosa and at the same time, the most peripheral part of the tooth-supporting apparatus.

It covers the coronal part of the alveolar process, passes over the crest of the alveolar bone and interdental septa and encircles the necks of teeth

Gingiva or Marginal Epithelium

Histological Characteristics of a Normal Marginal Periodontium“free” gingiva ends on the enamel surface at a shallow angleGingival sulcus is less than 0.2 mm depth or is absentThe junctional epithelium contains only a few isolated leukocytesCollagen Ct fibers extend directly alongside the junctional epithelium all the way to just under the gingival marginNo signs of acute inflammation or chronic cellular infiltration

Clinical Characteristic of Normal GingivaA pale, pink colorA smooth marginal and papillary gingivaAttached gingiva with distinct stipples in varying density.Firm consistency of all the tissues.The papillary gingiva reaches halfway to the incisal edge and fills the interdental space up to contact point.a fine probe without the use of apparent force.Sulcular fluid cannot be obtained on filter paper strips placed into the entrance to the sulcus

Gingiva or Marginal Epithelium

Normal gingiva that satisfies these criteria is not identical with “clinically healthy” gingiva

Two topographycally distinct zones:

Free gingivaa narrow band of tissue that follows the scalloped contour the necks of the teeth and the cementoenamel junction

is referred to as “free” because it can be moved mechanically along tooth surface as well as away from the tooth

has an epithelial attachment maintained by junctional epithelium along the tooth surface Separated from the attached gingiva by a slight indentation called the FREE GINGIVAL GROOVE, whose level corresponds approximately to that of the bottom of the gingival sulcusabout 1.1 mm in the primary dentition, about 1.5 mm, 0.8 – 1.8 mm in young adults and about 1.6 mm (0.9-2.1 mm) in older people

Marginal gingiva - that part of the free gingiva that tapers to a knife-like edge extending along the cervical level of the tooth on labial or buccal and lingual surfaces

Interdental gingival papilla – the bulges of gingival tissue on al occlusal direction in between teeth

Interdental col – the constriction in between the facial and lingual interdental gingival papilla

Gingival sulcus – a shallow groove extending around the circumference of the tooth

Depth varies from 0.6 mm and has the average depth of 1.8 mm

Attached GingivaIs part attached to the teeth and alveolar bone. It is bounded CORONALLY by the free gingival groove and APICALLY by the mucogingival junction

On the facial surface of both jaws, it is adjacent to the alveolar mucosaOn the lingual surface of the mandible it is adjacent to the floor of the mouthThe is NO attached gingiva on the palatal side of the maxilla since the immovable palatal mucosa extends all the way to the free gingivaExhibits many ovoid or elongated indentations called STIPPLES – reflects the arrangement, thickness and frequency of the rete ridges

Density varies between individuals

Especially pronounced on the anterior region of the maxilla

Absent in children younger that 6 years; and is present only 35% of children aged 5 – 13 years

GINGIVAL SULCUS

FREE GINGIVA

GINGIVAL GROOVE

ATTACHED GINGIVA

ALVEOLAR MUCOSA

Dentogingival Junction

Represents a unique anatomic feature concerned with attachment of the gingiva to the toothEctodermal in originConsist of fundamental 3 compartments:

Junctional epitheliumOral sulcular epitheliumOral gingival epithelium

Gingival Ligament or Supra-Alveolar Fiber Apparatus

Dentogingival fibersDentoperiosteal fibersAlveologingival fibersCircular an Semicircular fibersTranseptal fibersTransgingival and Intergingival fibersInterpapillary fibersPeriosteogingival fibersIntercircular gibers

1. Dentogingival fibers

The most numerous, consists of three groups:

First group extends from the cementum in an obliquely coronal directionSecond group streams horizontal from the cementum into the free marginal gingivaThird group, many of which run parallel with the dentoperiosteal fibers, curve from the cementum apically over the alveolar crest

1. Dentogingival fibers

FIRST

SECOND

THIRD

2. Dentoperiosteal Fibers

Insert into the supra-alveolar cementum at the same level as the transeptal fibers, pass apically over the crest of the alveolar bone into the periosteum of the outer and inner plates of the alveolar process

3. Alveologingival fibers

Insert into the crest of the alveolar bone, course coronally and enter the free and attached sections of the marginal and interdental gingiva

4. Circular and Semicircular fibers

Circular – small group of fibers that forms a band around the neck of the tooth helping to bind the free gingiva into the tooth

Semicircular – encircle only the vestibular or oral half of the root; lie apical to the circular fibers

5. Transeptal Fibers

Also called INTERDENTAL FIBERSBind the supra-alveolar cementum of one tooth to that of the adjacent toothImplicated as a major cause of post retention relapse of orthodontically positioned teeth

6. Transgingival and Intergingival fibers – reinforce the circular and semicircular

Transgingival – identical with semicircular, insert interdentally into a supra-alveolar cementum, pass obliquely through the interdental tissue stream into the free gingiva of the adjacent tooth where they may unite with the circular fiber

6. Transgingival and Intergingival fibers – reinforce the circular and semicircular

Intergingival – form a continuous series of fibers running under the epithelium along both the vestibular and oral aspects of the dental arch converging distal to the last molar

7. Interpapillary fibers

Cross through the free portion of interdental gingival tissue in an orovestibular direction to tie the oral and vestibular gingival papillae together

Periosteogingival fibersInsert into the periosteum of the outer and inner cortical plates of the alveolar process and pass facially and orally into the section of all attached gingiva lying over it

Intercircular fibersAre located on the vestibular and oral sides of the interdental gingiva and connect the circular fiber bundles of neighboring teeth. They form part of the Intergingival fiber bundles

Alveolar Mucosa

The gingival mucosa joins the alveolar mucosa at the mucogingival junctionIt is present only in the vestibular region and extends from the scalloped mucogingival junction to the vestibular fornix, where it is continuous with the mucosa covering the lips and cheeksThe alveolar mucosa is movable, can be lifted to a limited extent from its base and exhibits structural deep red in color and has a smooth surface

Hard Palate

Is the roof of the mouth and is supported by the palatine processes of the maxillary and horizontal parts of the palatine bone

At the level of the alveolar tuberosity, it joins the soft palate

The hard palate is pale pink

On the surface of the hard palate, the midline is known as MEDIAN RAPHE - fusiform mucosal mass and forming the midline of the palate and represent the fusion area of the palatine processes INCISIVE PAPILLA - oral mass of tissue capping the opening of incisive canal containing oral part of the nasopalatine duct On each side of the median raphe are ridges of tissue called TRANSVERSE RIDGES OR PALATINE RUGAE AND RUGAE PALATINI - ridges of mucous membrane with dense connective tissue core extending laterally from the incisive papillae and the anterior raphe

Specialized Mucosa

Dorsum of the tongue

Covered by a stratified squamous keratinizing epithelium

Consists of four types pf epithelial structures called papilla:

Filiform papilla – most numerous; arranged in rows

Fungiform papilla – fewer, distributed along the filiform; numerous near the tips of the tongue; contains taste buds

Circumvallate papilla – distributed along the V-shaped sulcus between the body and the base; 3 mm in diameter; contains taste buds

Foliate papilla – 4 – 11 vewrtical grooves or furrows on the lateral posterior sides of the tongue; contains taste buds

Taste Buds

Microscopically visible barrel-shaped bodies

Contains the chemical sense of taste

Generally associated with the papilla of the tongue – circumvallate, foliate, and fungiform, although some are distributed in the soft palate, epiglottis, larynx, and pharynx

Types of taste cells – found among the 10 – 14 cells in the taste bud

Supporting or Sustentacular cellsTall columnar cell; lie at the periphery of the taste bud

Taste cells/chief cells – tall columnar cells that bear either elongated microvilli that project into the taste pore or ones with shortened villi that open into the base of the pore

Each are associated with nerves

Basal cellsAre in close proximal contact with the basal lamina

Rapid turn-over of cells in the taste bud – approximately 10 days

Four taste sensations are sweet, salty, sour and bitter

Location of taste perception on the tongue and soft palate