SALIVARY GLANDSSALIVARY GLANDS

Oral Histology Oral Histology Dent 205Dent 205

Summer semesterSummer semester2005/20062005/2006

Salivary GlandsSalivary Glands CharacteristicsCharacteristics

Compound – more than one tubule entering the main ductCompound – more than one tubule entering the main duct Tubuloacinar – morphology of secreting cellsTubuloacinar – morphology of secreting cells Merocrine – only secretion of the cell is releasedMerocrine – only secretion of the cell is released Exocrine – secretion onto a free surfaceExocrine – secretion onto a free surface

PhysiologyPhysiology Stimulants-taste and masticationStimulants-taste and mastication Autonomic nervous system – Afferent nervesAutonomic nervous system – Afferent nerves Salivary centreSalivary centre Autonomic nervous system – Efferent nervesAutonomic nervous system – Efferent nerves SecretionSecretion

Classification of Salivary GlandsClassification of Salivary Glands SizeSize

MajorMajor ParotidParotid SubmandibularSubmandibular SublingualSublingual

Minor: scattered throughout the oral Minor: scattered throughout the oral mucosamucosa

Labial, buccal, palatoglossal, palatal, and Labial, buccal, palatoglossal, palatal, and lingual mucosaelingual mucosae

Not present in gingivae and dorsum of Not present in gingivae and dorsum of anterior 2/3 of the tongueanterior 2/3 of the tongue

SecretionSecretion MucousMucous Serous Serous MixedMixed

SalivaSaliva

ConstituentsConstituents Water-99%Water-99% OrganicOrganic

ProteinsProteins GlycoproteinsGlycoproteins EnzymesEnzymes

InorganicInorganic MineralsMinerals

SalivaSaliva

FunctionsFunctions LubricationLubrication

MucinMucin Physical protection of oral mucosaPhysical protection of oral mucosa

TasteTaste Antibacterial and immunityAntibacterial and immunity

LysozymeLysozyme IgA – produced by plasma cellsIgA – produced by plasma cells

DigestionDigestion AmylaseAmylase

BufferingBuffering MineralsMinerals Helps in maintaining the integrity of enamelHelps in maintaining the integrity of enamel

Wound healing and upper GI mucosal integrityWound healing and upper GI mucosal integrity Epidermal Growth Factor – produced and secreted by the submandibular salivary glandsEpidermal Growth Factor – produced and secreted by the submandibular salivary glands

Blood coagulationBlood coagulation KallikreinKallikrein

Salivary GlandsSalivary Glands Main tissue elementsMain tissue elements

Glandular secretory tissueGlandular secretory tissue ParenchymaParenchyma EctodermalEctodermal Acini and duct epitheliumAcini and duct epithelium

Supporting Connective tissueSupporting Connective tissue StromaStroma MesodermalMesodermal

Macro-to-microscopic levelsMacro-to-microscopic levels GlandGland LobeLobe LobuleLobule Secretory units – AciniSecretory units – Acini

The Secretory Units The Secretory Units - ACINI- ACINI

A grape-like cluster of A grape-like cluster of parenchymal cells around a parenchymal cells around a lumenlumen

TypesTypes SerousSerous MucousMucous MixedMixed

Serous demilunes capping Serous demilunes capping mucous cellsmucous cells

Myoepithelial cells around the Myoepithelial cells around the aciniacini Contactile cells with several Contactile cells with several

processesprocesses Synonyms: basket cellsSynonyms: basket cells

The Duct SystemThe Duct System Intra-lobularIntra-lobular

Acinus lumenAcinus lumen Intercalated ductsIntercalated ducts Striated ductStriated duct* In intra-lobular system, * In intra-lobular system,

composition is affectedcomposition is affected Plasma cells in stromaPlasma cells in stroma ElectrolytesElectrolytes Epidermal GF and KallikreinEpidermal GF and Kallikrein

Inter-lobular Inter-lobular Collecting ductsCollecting ducts*The inter-lobular system is inert, *The inter-lobular system is inert,

does not affect the compositiondoes not affect the composition

StromaStroma

Connective tissueConnective tissue Mesenchymal originMesenchymal origin Macro-to-microscopic levelsMacro-to-microscopic levels

CapsularCapsular Inter-lobar Inter-lobar Inter-lobularInter-lobular Inter-acinousInter-acinous

Capsular, inter-lobar, and inter-Capsular, inter-lobar, and inter-lobular septa contain blood vessels lobular septa contain blood vessels and nervesand nerves

ConstituentsConstituents Collagen fibersCollagen fibers FibroblastsFibroblasts Fat cellsFat cells

With age, there is a decrease in With age, there is a decrease in parenchyma and an increase in parenchyma and an increase in stroma (esp. far cells)stroma (esp. far cells)

Synthesis of SalivaSynthesis of Saliva

Active secretory processActive secretory process Not a blood ultra-filtrateNot a blood ultra-filtrate Serous cellsSerous cells

Watery proteinaceous fluid contains amylaseWatery proteinaceous fluid contains amylase Mucous cellsMucous cells

Proteins linked to a greater amount of carbohyratesProteins linked to a greater amount of carbohyrates Plasma cellsPlasma cells

IgAIgA

Secretion of SalivaSecretion of Saliva Throughout the dayThroughout the day

Low level in generalLow level in general Periodic large addition from major glandsPeriodic large addition from major glands

Average flow rate (90% from Major SG)Average flow rate (90% from Major SG) 0.3 ml/min0.3 ml/min 500-700 ml/day500-700 ml/day

Contribution of gingival fluidsContribution of gingival fluids SecretionSecretion

SpontaneousSpontaneous Small amounts from sublingual and minor SGsSmall amounts from sublingual and minor SGs

Stimulated (nerve-mediated)Stimulated (nerve-mediated) The bulk of saliva from all glandsThe bulk of saliva from all glands Parotid and Submandibular SGs do not secret spontaneouslyParotid and Submandibular SGs do not secret spontaneously

Anaesthesia ceases secretion as it is nerve-mediatedAnaesthesia ceases secretion as it is nerve-mediated

Serous cellsSerous cells

Light MicroscopyLight Microscopy Basophilic because of Rough Basophilic because of Rough

Endoplasmic ReticulumEndoplasmic Reticulum Characteristic granular appearance Characteristic granular appearance

with H & Ewith H & E Round prominent nuclei located at the Round prominent nuclei located at the

basal third of the cellbasal third of the cell Ultra-structureUltra-structure

Wedge-shaped outlineWedge-shaped outline Basal lamina separates from stromaBasal lamina separates from stroma Luminal part contains zymogen Luminal part contains zymogen

granulesgranules MicrovilliMicrovilli Desmosomes, gap and tight junctionsDesmosomes, gap and tight junctions

Mucous cellsMucous cells

Appear pale in H & E stainsAppear pale in H & E stains Basally-compressed nucleiBasally-compressed nuclei Acini may be surrounded Acini may be surrounded

by crescent-shaped serous by crescent-shaped serous demilunesdemilunes

Debate whether demilunes Debate whether demilunes are connected with the are connected with the lumenlumen

Mucin granulesMucin granules

Acinus lumen

Serous demilunes

Mucous cells

Myoepithelial cellsMyoepithelial cells

Lie between basal lamina and basal Lie between basal lamina and basal membranes of acinar cells and ICDmembranes of acinar cells and ICD

Around acinar cellsAround acinar cells DendriticDendritic Long tapering processesLong tapering processes

Around ICDAround ICD LongitudinalLongitudinal Few short processesFew short processes

ContracttionContracttion ParasympatheticParasympathetic SympatheticSympathetic

Ultra-structureUltra-structure Flattened nucleusFlattened nucleus Desmosomes with parenchymal cellsDesmosomes with parenchymal cells Gap junctions and hemidesmosomes with Gap junctions and hemidesmosomes with

basal laminabasal lamina

Intercalated ductsIntercalated ducts

Drainage from several aciniDrainage from several acini Compressed between the aciniCompressed between the acini Cuboidal epithelial cellsCuboidal epithelial cells Prominent nucleiProminent nuclei In Parotid, they are long, In Parotid, they are long,

narrow, and branchingnarrow, and branching

Striated ductsStriated ducts

Larger and longer than ICDLarger and longer than ICD Simple columnar epitheliumSimple columnar epithelium Cells have large centrally-located nucleiCells have large centrally-located nuclei Luminal surfaces have microvilliLuminal surfaces have microvilli Basal surfaces separated from Basal surfaces separated from

connective tissue by basal laminaconnective tissue by basal lamina Striation (in light microscopy) Striation (in light microscopy)

corresponds to multiple infoldings of corresponds to multiple infoldings of the basal membrane of the cellsthe basal membrane of the cells

DesmosomesDesmosomes Electrolyte re-absorption (active) and Electrolyte re-absorption (active) and

secretionsecretion Secretion of Epidermal GF and Secretion of Epidermal GF and

KallikreinKallikrein

Collecting ductsCollecting ducts Bi-layered epithelium (lacks Bi-layered epithelium (lacks

striation)striation) Columnar epithelial layerColumnar epithelial layer Basal layerBasal layer

As it enlarges, it gets a As it enlarges, it gets a connective tissue adventitiaconnective tissue adventitia

Terminated as stratified Terminated as stratified epithelium to merge with the epithelium to merge with the oral mucosaoral mucosa

Parotid glandParotid gland

The largestThe largest Serous AciniSerous Acini Adult PG vs. Infant’s PGAdult PG vs. Infant’s PG Fat cells vs. ageFat cells vs. age

Submandibular Submandibular glandgland

22ndnd largest largest Mixed serous-Mixed serous-

mucous secretion mucous secretion (7:3)(7:3)

Intercalated ducts Intercalated ducts are short and are short and difficult to locatedifficult to locate

Striated ducts are Striated ducts are long and obvious long and obvious

Sublingual glandsSublingual glands 2 segments all empty 2 segments all empty

to the sublingual foldto the sublingual fold Major sublingual glandMajor sublingual gland 8 - 30 mixed minor SGs8 - 30 mixed minor SGs

Mixed gland, mucous Mixed gland, mucous outnumber serous cellsoutnumber serous cells

Most of the serous Most of the serous cells are in demilunescells are in demilunes

Lacking striated ductsLacking striated ducts

Minor Salivary glandsMinor Salivary glands

Primarily mucousPrimarily mucous Labial, buccal, palatal, palatoglossal, and Labial, buccal, palatal, palatoglossal, and

linguallingual Lingual glandsLingual glands

Anterior glandsAnterior glands Embedded in muscle near the ventral surface of the Embedded in muscle near the ventral surface of the

tonguetongue Mucous glandsMucous glands

Posterior glandsPosterior glands At the root of the tongueAt the root of the tongue Mucous glandsMucous glands

Von Ebner glandsVon Ebner glands SerousSerous Associated with the Circumvallate papillaeAssociated with the Circumvallate papillae

Clinical ConsiderationsClinical Considerations Dry Mouth (xerostomia)Dry Mouth (xerostomia)

CausesCauses Ageing – Parenchymal tissue < StromaAgeing – Parenchymal tissue < Stroma DrugsDrugs

Central action on the salivary centreCentral action on the salivary centre Diuretics, sedatives, hypnotics, antihistamines, antihypertensives, Diuretics, sedatives, hypnotics, antihistamines, antihypertensives,

antipsychotics, antidepressants, anticholinergics, and appetite suppressantsantipsychotics, antidepressants, anticholinergics, and appetite suppressants Loss / destruction of salivary tissueLoss / destruction of salivary tissue

RadiotherapyRadiotherapy Autoimmune disordersAutoimmune disorders

Sjogren’s syndrome – destruction by lymphoid tissue (autoimmune disease)Sjogren’s syndrome – destruction by lymphoid tissue (autoimmune disease) Salivary gland surgerySalivary gland surgery

Endocrine disordersEndocrine disorders DiabetesDiabetes HyperthyroidismHyperthyroidism

Clinical Considerations Clinical Considerations

Dry mouth (xerostomia)Dry mouth (xerostomia) Signs and symptomsSigns and symptoms

Dry, red, glossy atrophic mucosaDry, red, glossy atrophic mucosa Difficulty chewing, swallowing, or speakingDifficulty chewing, swallowing, or speaking Altered / diminished taste abilityAltered / diminished taste ability Dental cariesDental caries

Saliva contains re-mineralising mineralsSaliva contains re-mineralising minerals Periodontal diseasePeriodontal disease Candidal infectionCandidal infection

TreatmentTreatment Consider stopping offending medication Consider stopping offending medication Commercial saliva substituteCommercial saliva substitute Fluoride SupplementationFluoride Supplementation Scrupulous dental careScrupulous dental care

Clinical considerationsClinical considerations Obstructive disordersObstructive disorders

Sialolithiasis (salivary calculi)Sialolithiasis (salivary calculi) 80% in submandibular SG80% in submandibular SG

Mucoceles and cystsMucoceles and cysts Minor SGsMinor SGs Retention of mucous outside the ductRetention of mucous outside the duct

RanulaRanula Submandibular and sublingual SGsSubmandibular and sublingual SGs

Inflammatory disorders (Sialadenitis)Inflammatory disorders (Sialadenitis) Viral Viral

MumpsMumps Bacterial – uncommonBacterial – uncommon

Suppurative parotitisSuppurative parotitis Autoimmune diseasesAutoimmune diseases

Sjogren’s syndromeSjogren’s syndrome Salivary gland tumoursSalivary gland tumours

http://www.fo.usp.br/estomato/patobucal/images/mucocele.jpg

http://www.infocompu.com/adolfo_arthur/images/ranula.jpg