Oral Mucosa

ORAL MUCOSAOral HistologyOral Histology

Dent 206Dent 206

Functions of oral Mucosa Mechanical protection Barrier against microorganisms & toxins Immunological defense Lubrication Innervation

Touch Proprioception Taste Pain

Structure of Mucosa

Epithelium (vs. epidermis of skin) Stratified squamous Ectodermal or endodermal origin

Basal lamina Lamina Propria (vs. dermis of skin)

Papillary Layer Reticular layer

Submucosa (vs. subcutaneous tissue) Loose connective tissue Contains

Glandular tissue Adipose tissue Large blood vessels and nerves

Types of Oral Mucosa

Masticatory muscosa Lining mucosa Specialized mucosa

Masticatory Mucosa Where there is compression & friction Rough, thicker and whiter in colour compared to

lining mucosa Keratinized or parakeratinized epithelium Thick lamina propria bound down directly &

tightly to underlying bone Covering

Hard palate Oral surface of gingiva

Lining Mucosa Not subject to high level of friction Soft, mobile and distensible Thinner & redder in colour compared to

masticatory mucosa Non-keratinized epithelium Loose lamina propria Covering

Oral surface of cheeks, lips, alveolus, dentogingival region, floor of the mouth, ventral surface of tongue and soft palate

Specialized mucosa

Keratinized epitheliumCovers

Dorsum of the tongueAssociated with taste sensationGustatory mucosa

Vermilion zone of the lip

Epithelium Layers

Stratum germinativum (stratum basale)

Stratum spinosum (prickle cell layer)

Stratum granulosum (granular layer) Stratum corneum (Keratinized or

cornified layer) Progressive maturation /

differentiation process Superficial cells are shed & replaced

from below Turnover is fastest in junctional &

sulcular epithelia (5 days) Followed by lining mucosa Masticatory mucosa has the slowest

turnover rate

Stratum germinativum Single cuboidal cell layer Adjacent to lamina propria The only layer where

mitosis occurs Are all stem cells? Least differentiated cells Non-keratinocytes

Stratum spinosum Several cells thick Round or ovoid cells Larger & more mature than

those of s. germinativum Contain

Tonofilaments & involucrin Phospholipid granules (Odland

bodies) in upper part of stratum spinosum

Increased desmosomes (shrinkage during preparation gives the spiny appearance)

Stratum granulosum Cells of further increase in maturation Cells larger & flatter Contain

Tonofilaments & tonofibrils that occupy the cytoplasm

Keratohyaline granules (contain profilaggrin)

Stratum Corneum In keratinized epithelium

Highly mature epithelial cells (squames) All cellular organelles and nucleus lost (orthokeratinzation) In gingiva, nuclei may be retained (parakeratinization) Cells are packed with Keratin Kertain consists of

Tonofilaments surrounded by Filaggrin (matrix protein)

Desmosomes are weakened to allow for shedding (desquamation)

Involucrin is cross-linked to form a cornified envelop beneath plasma membrane

Stratum Corneum In non-keratinized epithelium

No keratin Tonofilaments are less & under-

developed Lack keratohyaline granules This layer is less distinct The outer layers of non-kertinized

epithelium may be termed stratum superficiale

The layers below may be termed stratum intermedium

Keratinization

Regional distribution Adaptation to abrasion by food - rough

surface Whiter than nonkeratinized mucosa Ortho- vs. parakeratinization

Non-keratinocytes 10% of oral epithelial cells Lack tonofilaments & desmosomes (except

Merkel cells) Appears as clear cells in routine H&E staining

as they lack the cytokeratin of keratinocytes Include

Melanocytes Langerhans cells Merkel cells

Melanocytes Located in stratum germinativum Pigment (melanin)-producing cells Derived from neural crest cells Long processes that extend through upper layers Packed with granules (melanosomes) Racial variance is due to

Melanocyte size difference Number of dendritic processes Melanosomes: granule number or size Melanin: degree of dipersion and rate of degradation

Langerhans cells Dendritic cells Located in the layers above stratum

germinativum Derived from bone marrow precursors Antigen-presenting cells Involved in contact-hypersensitivity reactions,

antitumour immunity & graft rejection Contain Birbeck granules

Merkel cells Located in stratum germinativum of

masticatory epithelium Absent in lining epithelium Closed apposed to nerve fibers Thought to act as receptors Derived from neural crest cells Associated with desmosomes

Lining mucosa Location

Mucosal surface of the Lip Soft Palate Cheeks Ventral surface of the tongue Floor of the mouth Alveolar Mucosa Frena Vestibular Fornix

Lining epithelium

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/09_big.html

Lip Oral surface Vermilion zone Skin surface

Oral surface

Epitheliumnonkeratinized

Lamina PropriaSeromucous minor salivary glands

SubmucosaOrbicularis Oris

Oral surface of the lip

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/15_big.html

Vermilion zone Junction between skin & oral mucosa Specialized keratinized mucosa different from both skin &

oral mucosa Lacks hair follicles or glandular tissue Sebaceous glands may be present at angles of the mouth Red in colour (human characteristics)

Thin epithelium Transparent Eleidin Rich blood vessels near the surface (long papillae)

Intermediate zone Junctional region with oral surface Parakeratinized

Vermilion zone

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/18_tns.html

Skin surface Skin appendages

Hair follicles Sebaceous glands Erector pili muscles Sweat glands

Subcutaneous layer Orbicularis Oris

Skin surface of the lip

Fordyce’s spots Ectopic sebaceous glands Not associated with a hair follicle Location

Corners of the mouth Buccal mucosa Soft palate

Fordyce’s spots

http://www.usc.edu/hsc/dental/PTHL501/QL/d_ql_11.html

Fordyce’s spots

http://www.usc.edu/hsc/dental/PTHL501/QL/d_ql_14.html

Soft palate Epithelium

Pink surface Lamina Propria

Highly vascularized Submucosa

Muscles Mucous minor salivary glands

Cheeks Epithelium Lamina Propria Submucosa

Fat cells Seromucous minor salivary glands Buccinator muscle

Ventral surface of the tongue Epithelium Lamina Propria Submucosa

Connective tissue and muscle fibers mixed together

*Firmly attached membrane

Ventral surface of the tongue

Floor of the mouth

Epithelium lamina Propria Submucosa

Minor salivary glands Sublingual major salivary glands

*Loosely attached membrane

Alveolar mucosa Epithelium

Nonkeratinized Lamina Propria

Dermal papillae are short and thick Numerous elastic fibers

Submucosa Loose and may contain seromucous glands

Periosteum /bone

Vestibular fornix and frena Fornix

Loosely attached to muscle Frena

Labial/buccal Folds of mucous membrane Contain connective tissues No muscles

Masticatory Mucosa Location

Gingiva Hard palate

Masticatory epithelium

Attachments Cell-to-cell

Desmosomes Epithelium to

Lamina Propria Basal Lamina

Hemidesmosomes Anchoring Fibrils

Gingiva Development

Coalescence of reduced enamel epithelium & oral epithelium

Three zones Free (marginal) gingiva Attached gingiva Interdental gingiva

Junctions Free gingival groove mucogingival junction

http://home.teleport.com/~bobh/gingiva.htm

Free gingiva

Free gingiva Surface

Smooth Keratinized Sulcular surface is not keratinized

Separated by: Gingival sulcus from the tooth Free gingival groove from the attached

gingiva

Free gingiva

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/18_tns.html

Free gingiva

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/18_tns.html

Free gingival - oral Surface

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/18_tns.html

Attached gingiva Surface

Stippled Separated by:

Free gingival groove from the free gingiva

Mucogingival junction from alveolar mucosa

No submucosa Periosteum/ bone

Junctional epithelium

Functions Floor of gingival sulcus Attachment Protection

Different cells Fewer desmosomes High rate of turnover High metabolic activity Stratum Germinativum

cells: hemidesmosomes

Junctional epithelium

http://www.usc.edu/hsc/dental/ohisto/Cards/muc/18_tns.html

Interdental papilla and col Interdental papilla

Facial or lingual parts of gingiva between teeth Col

Epithelium of the interproximal gingival tissue connecting facial and lingual interdental papillae

Thin Nonkeratinized Concave in shape

Hard palate Epithelium

Keratinized Lamina Propria

Dense under rugue Submucosa

Fatty cells in anterior lateral area Mucous glands in the posterior lateral area Absent in the midline under median raphe

Periosteum

http://www1.us.elsevierhealth.com/SIMON/Bird/modern/EIC/graphics/7627_17_14.jpg

Rugae Epithelial folds

Function Mastication Phonation

Traction Bands Bundles of collagen

fibers in LP origin: bony palate Insertion: papillary

fibers of LP Function: anchorage

www.forsyth.org/oralpathology/ case_008b.htm

Palatal mucosa

Specialized gustatory mucosa

Location Dorsum of the tongue

4 types of papillae Filiform

Fungiform Circumvallate Foliate

Filiform and fungiform papillae

www.forsyth.org/oralpathology/ case_086b.htm

Filiform papillae Anterior 2/3s of the dorsum of

the tongue Central cores of lamina propria

covered by Ortho or parakeratinized epithelium

No taste buds Fungiform papillae

Mushroom-shaped Vascular core of lamina propria

covered by keratinized or non-keratinized epithelium

Taste buds may be found on the surface

Filiform & fungiform papillae

Circumvallate papillae

www.forsyth.org/oralpathology/ case_011.htm

Located in the posterior region of anterior 2/3 just in front of sulcus terminalis

Large & rounded Surrounded by a trench-like feature Do not project over the surface Covered by non-keratinized epithelium Taste buds found on the internal wall of

the trench Associated with Von Ebner glands

Serous minor salivary glands Empty at the floor of the trench

Von Ebner’s Glands (serous glands)

Foliate papillae

http://www.forsyth.org/oralpathology/case_010.htm

At the side of posterior 1/3 of the tongue One or two longitudinal clefts Tastes buds found within the non-keratinized

parts

Foliate papillae

http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab17/Images/digl10.jpg

Papillae of the TonguePapillae ofthe tongue

Num-ber

Locat-ion

shape Tastebuds

Kerat-inized

Serousglands

Inner-vationof tastecells

Func-tion

FiliformPapillae

majority anterior 2/3of thedorsum ofthe tongue

slenderthreadlike 2-3mm long

no tastebuds

yes no no give theroughmastica-torysurface ofthe tongue

Fungi-formPapillae

few, morenumerousnear thetip of thetongue

inter-spersedbetweenfiliform inthe anterior2/3

mushroomshaped

on thesuperiorsurface

no no Chordatympani

taste

Circum-vallatePapillae

10-14 Justanterior tothe V-shapedsulcusbetweenthe bodyand thebase of thetongue

large 3mm indiameter witha surroundingtrench

on thewalls

yes VonEbner’sglands

Glosso-pharyngealnerve

taste

FoliatePapillae

4-11 Lateralposteriorpart of thetongue

verticalgooves orfurrows

on thewalls

yes yes Glosso-pahryngealnerve

taste

Taste buds Barrel-shaped organs in epithelium Neuroepithelial vs. epithelial cells associated

with sensory nerve endings Chemical response Rapid turnover/ 10 days

Taste buds

Location Tongue

associated with the papillae Soft Palate Pharynx Epiglottis Larynx

Taste Buds Taste Pore Cell types (10-14/bud)

Supporting Cells (sustentacular cells) Taste Cells

Type 1(dark) Type 2 (light) Type 3

Basal cells Type 4 Precursors

Taste buds

Taste buds

Taste buds

Taste sensations 4 types

Sweet Salt Sour Bitter

Regional Sensitivity Role of

Oder/olfaction Temperature

Innervations of taste Buds Chorda tympani of facial nerve

Fungiform papillae Glossopharyngeal nerve

Vallate and foliate papillae soft palate pharynx

Vagus nerve Epiglottis Larynx

Innervations of lingual taste buds

www.biology.eku.edu/RITCHISO/ tastebud.html

Nerves and blood vessels Submucosa

Primary plexus of larger vessels and nerves Lamina Propria (dermal papillae)

Secondary plexus of terminal nerve endings and capillary loops

Encapsulated touch and temperature endings Axons associated with Merkel’s cells

Epithelium Avascular Free endings associated with pain

Nerves and Blood Vessels

online-media.uni-marburg.de/ .../HIS/txt/skin/skin02.htm