Core Features

• Embryologyofthesalivaryglandsandtheiras-sociatedstructures

• Detailedanatomyoftheparotid,submandibular,sublingual,andminorsalivaryglands,includingnervousinnervation,arterialsupply,andvenousandlymphaticdrainage

• Histologyandorganizationoftheaciniandductsystemswithinthesalivaryglands

• Physiology and function of the glands with re-specttotheproductionofsaliva

• Considerationswhentakingapatient’shistory

• The intra- and extraoral aspects of inspectionandpalpationduringaphysicalexamination

Chapter

 Anatomy, Function, and Evaluation of the Salivary GlandsF. Christopher Holsinger and Dana T. Bui

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Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

DevelopmentalAnatomy . . . . . . . . . . . . . . . . . . . . . . . . . . 2

ParotidGland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Fascia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Stensen’sDuct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

NeuralAnatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

AutonomicNerveInnervation . . . . . . . . . . . . . . . . . . . 4

ArterialSupply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

VenousDrainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

LymphaticDrainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

ParapharyngealSpace . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

SubmandibularGland . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Fascia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Wharton’sDuct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

NeuralAnatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

ArterialSupply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

VenousDrainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

LymphaticDrainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

SublingualGland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

MinorSalivaryGlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Histology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

PhysiologyofSalivaryGlands . . . . . . . . . . . . . . . . . . . . . 11

EvaluationoftheSalivaryGlands . . . . . . . . . . . . . . . . . . 13

History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

PhysicalExamination . . . . . . . . . . . . . . . . . . . . . . . . . . 13

RadiologicandEndoscopicExaminationoftheSalivaryGlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Introduction

Thehumansalivaryglandsystemcanbedividedintotwodistinct exocrine groups . The major salivary glands in-cludethepairedparotid,submandibular,andsublingualglands .Additionally,themucosaoftheupperaerodiges-tive tract is lined by hundreds of small, minor salivary glands . The major function of the salivary glands is tosecrete saliva, which plays a significant role in lubrica-tion,digestion,immunity,andtheoverallmaintenanceofhomeostasiswithinthehumanbody .

Developmental Anatomy

In the last 15years, significant improvement has beenmade in our understanding of the molecular basis ofsalivaryglanddevelopment,supplantingandexpandingclassicalteachingintheembryologyanddevelopmentalanatomy .

Earlyworksuggeststhatdevelopmentofthesalivaryglandsbeginsduringthesixthtoeighthembryonicweekwhenoralectodermaloutpouchingsextendintothead-jacentmesodermandserveasthesiteoforiginformajorsalivaryglandgrowth .Thedevelopmentofmajorsalivaryglands is thought toconsistof threemainstages [1,8] .Thefirststageismarkedbythepresenceofaprimordialanlage(fromtheGermanverbanlagen,meaningtolayafoundationortoprepare)andtheformationofbranchedductbudsduetorepeatedepithelialcleftandbuddevel-opment . Ciliated epithelial cells form the lining of thelumina,whileexternalsurfacesare linedbyectodermalmyoepithelial cells [2] . The early appearance of lobulesand duct canalization occur during the second stage .Primitiveacinianddistalductregions,bothcontainingmyoepithelial cells, form within the seventh month ofembryoniclife .Thethirdstageismarkedbymaturationoftheaciniandintercalatedducts,aswellasthedimin-ishingprominenceofinterstitialconnectivetissue .

Thefirstoftheglandstoappear,duringthesixthges-tationalweek,istheprimordialparotid gland .Itdevelopsfromtheposteriorstomodeum,whichlaterallyelongatesinto solidcordsacross thedevelopingmassetermuscle .Thecordsthencanalizetoformducts,andaciniareformedat the distal ends . A capsule formed from the ambientmesenchymesurroundstheglandandassociatedlymphnodes[14] .Smallbudsappearinthefloorofthemouthlateraltothetongueduringthesixthweekofembryonic

lifeandextendposteriorlyaroundthemylohyoidmuscleinto the submandibular triangle . These buds eventuallydevelop into the submandibular glands . A capsule fromthesurroundingmesenchymeisfullydevelopedaroundtheglandbythethirdgestationalmonth[8] .Duringtheninth embryonic month, the sublingual gland anlage isformedfrommultipleendodermalepithelialbudsintheparalingualsulcusofthefloorofthemouth .Absenceofacapsuleisduetoinfiltrationoftheglandsbysublingualconnective tissue . Intraglandular lymph nodes and ma-jorductsalsodonotgenerallydevelopwithinsublingualglands .Upperrespiratoryectodermgivesrise tosimpletubuloacinarunits .Theydevelopintotheminor salivary glandsduringthe12thintrauterineweek[17] .

Recent work using murine models has shown thecomplexity of the underlying molecular events orches-trating classical embryological findings . Developmentof the salivary glands is an example of branching mor-phogenesis, a process fundamental to many developingorgans, including lung, mammary gland, pancreas, andkidney[12] .Branchingorgansdevelopacomplexarbo-rization and morphology through a program of repeti-tive,self-similarbranchingforkstocreatenewepithelialoutgrowths .Thedevelopmentalgrowthofamulticellularorgansuchasasalivaryglandisbasedonasetofinterde-pendentmechanismsandsignalingpathways .Theresult-ingexpressionofthesepathwaysisdynamic,organized,and changes correspondingly with each developmentalstage . The sonic hedgehog (Shh) signaling plays an es-sentialroleduringcraniofacialdevelopment[13] .Otherpathways,includingthefibroblastgrowthfactorfamilyofreceptorsandassociatedligands,havealsobeenshowntoplayacrucialrole[28] .

Parotid Gland

Anatomy

Thepairedparotidglandsarethelargestofthemajorsali-varyglandsandweigh,onaverage,15–30g .Located inthepreauricularregionandalongtheposteriorsurfaceofthemandible,eachparotidglandisdividedbythefacialnerve into a superficial lobe and a deep lobe (Fig .1 .1) .The superficial lobe, overlying the lateral surface of themasseter,isdefinedasthepartoftheglandlateraltothefacialnerve .Thedeep lobe ismedial to the facialnerveandlocatedbetweenthemastoidprocessofthetemporal

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boneandtheramusofthemandible .Mostbenignneo-plasmsarefoundwithinthesuperficial lobeandcanberemovedbyasuperficialparotidectomy .Tumorsarisinginthedeeplobeoftheparotidglandcangrowandextendlaterally, displacing the overlying superficial lobe with-out direct involvement . These parapharyngeal tumorscangrowinto“dumbbell-shaped”tumors,becausetheirgrowth is directed through the stylomandibular tunnel[5] .

Theparotidglandisboundedsuperiorlybythezygo-maticarch .Inferiorly,thetailoftheparotidglandextendsdownandabutstheanteromedialmarginofthesterno-cleidomastoidmuscle .This tailof theparotidglandex-tendsposteriorlyoverthesuperiorborderofthesterno-cleidomastoidmuscle toward themastoid tip .Thedeeplobeoftheparotidlieswithintheparapharyngealspace[10] .

Anaccessory parotid glandmayalsobepresent lyinganteriorlyoverthemassetermusclebetweentheparotidductandzygoma .Itsductsemptydirectlyintotheparotidductthroughonetributary .Accessoryglandulartissueishistologicallydistinct fromparotidtissue inthat itmaycontainmucinousacinar cells inaddition to the serousacinarcells[6] .

Fascia

Thedeepcervicalfasciacontinuessuperiorlytoformtheparotid fascia, which is split into superficial and deeplayers toenclose theparotidgland .Thethickersuperfi-cialfasciaisextendedsuperiorlyfromthemasseterandsternocleidomastoidmusclestothezygomaticarch .Thedeep layer extends to the stylomandibular ligament (or membrane), which separates the superficial and deeplobesoftheparotidgland .Thestylomandibularligamentisanimportantsurgicallandmarkwhenconsideringtheresection of deep lobe tumors . In fact, stylomandibulartenotomy [22] can be a crucial maneuver in providingexposure forenbloc resectionsofdeep-lobeparotidorother parapharyngeal space tumors . The parotid fasciaformsadenseinelasticcapsuleand,becauseitalsocoversthemassetermuscledeeply,cansometimesbereferredtoastheparotid masseteric fascia.

Stensen’s Duct

Theparotidduct,alsoknownasStensen’sduct,secretesaseroussalivaintothevestibuleoftheoralcavity .From

Fig. 1.1:Theparotidglandandthefacialnervebranching

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theanteriorborderofthegland,ittravelsparalleltothezygoma,approximately1cmbelowit,inananteriordi-rectionacrossthemassetermuscle .Itthenturnssharplytopiercethebuccinatormuscleandenterstheoralcavityoppositetheseconduppermolartooth .

Neural Anatomy

Thefacialnerve(CNVII)exitstheskullbaseviathesty-lomastoidforamen,whichisslightlyposterolateraltothestyloidprocessandanteromedialtothemastoidprocess .Beforeenteringtheposteriorportionoftheparotidgland,threemotorbranchesaregivenofftoinnervatethepos-teriorbellyofthedigastricmuscle,thestylohyoidmuscle,andthepostauricularmuscles .

Themaintrunkofthefacialnervethenpassesthroughtheparotidglandand,atthepes anserinus(Latin:goose’sfoot),divides intothetemporofacialand lowercervico-facialdivisionsapproximately1 .3cmfromthestylomas-toidforamen .Theuppertemporofacial divisionformsthefrontal, temporal, zygomatic, and buccal branches . Thelowercervicofacial divisionformsthemarginalmandibu-larandcervicalbranches .Branchesfromthemajorup-per and lower branches often anastomose to create thediversenetworkofmidfacialbuccalbranches .

The temporal branch traverses parallel to the super-ficial temporal vessels across the zygoma to supply thefrontalbellyof theoccipitofrontalismuscle, theorbicu-larisoculi,thecorrugatorsupercilii,andtheanteriorandsuperiorauricularmuscles .Thezygomatic branchtravelsdirectlyovertheperiosteumofthezygomaticarchtoin-nervatethezygomatic,orbital,andinfraorbitalmuscles .The buccal branch travels with Stensen’s duct anteriorlyoverthemassetermuscletosupplythebuccinator,upperlip,andnostrilmuscles .Buccalbranchescaneitherarisefromtheuppertemporofacialorthelowercervicofacialdivision .Themarginal mandibular branchcoursesalongtheinferiorborderoftheparotidglandtoinnervatethelowerlipandchinmuscles .Itliessuperficialtothepos-teriorfacialveinandretromandibularveinsintheplaneofthedeepcervicalfasciadirectlybeneaththeplatysmamuscle .Thecervical branchsuppliestheplatysmamuscle .Likethemarginalmandibularbranch,itislocatedwithintheplaneofthedeepcervicalfasciadirectunderneaththeplatysma .

Smallconnectionscanexistamongthetemporal,zy-gomatic,andbuccalbranches,andanatomicvariationsinfacial nerve branching patterns occur commonly . Each

terminalbranchcanbelocateddistallyandtracedretro-gradeacrosstheparotidglandtothemaintrunkofthefacialnerve .Thefacialnervecanalsobeidentifiedatthestylomastoidforamenbyperformingamastoidectomyifidentificationbytheusual landmarks isnotpossible[5,10,23] .

The great auricular nerve is a sensory branch of thecervical plexus, particularly C2 and C3, and innervatesthe posterior portion of the pinna and the lobule . Thenerveparallelstheexternaljugularveinalongthelateralsurfaceof the sternocleidomastoidmuscle to the tailoftheparotidgland,whereitsplitsintoanteriorandposte-riorbranches .Thegreatauricularnerveisofteninjuredduringparotidectomy,whichcanresultinlong-termsen-sory loss in the lobule . Harvesting of this nerve can beusedforfacialnervegraftingincertaincases .

The auriculotemporal nerve is a branch of the man-dibular nerve, the third inferior subdivision of the tri-geminalnerve(V3) .Afterexitingtheforamenovale,thenervetraversessuperiorlytoinnervatetheskinandscalpimmediatelyanteriortotheear .Itscourserunsparalleltothesuperficialtemporalvesselsandanteriortotheexter-nalauditorycanal .

Autonomic Nerve Innervation

The glossopharyngeal nerve (CNIX) provides visceralsecretory innervation to the parotid gland . The nervecarries preganglionic parasympathetic fibers from theinferior salivatory nucleus in the medulla through thejugular foramen (Fig .1 .2) . Distal to the inferior gan-glion, a small branch of CNIX (Jacobsen’s nerve) reen-ters theskull throughthe inferior tympaniccanaliculusand into the middle ear to form the tympanic plexus .Thepreganglionicfibers thencoursealongas the lesserpetrosalnerveintothemiddlecranialfossaandouttheforamen ovale to synapse in the otic ganglion . Postgan-glionicparasympatheticfibersexittheoticganglionbe-neaththemandibularnervetojointheauriculotemporalnerve in the infratemporal fossa .Thesefibers innervatetheparotidglandforthesecretionofsaliva .Postgangli-onic sympatheticfibers innervate salivaryglands, sweatglands,andcutaneousbloodvesselsthroughtheexternalcarotid plexus from the superior cervical ganglion . Ace-tylcholineservesas theneurotransmitter forbothpost-ganglionicsympatheticandparasympatheticfibers[10] .Thisphysiologiccoincidenceallowsforthedevelopmentof“gustatorysweating”(alsoknownasFrey’ssyndrome)

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followingparotidectomy[19,26] .Patientsdevelopsweat-ingandflushingoftheskinoverlyingtheparotidregionduring eating due to aberrant autonomic reinnervationofthesweatglandsbytheregeneratingparasympatheticfibers fromanyresidualparotidgland .Frey’s syndromemayoccurinasmanyas25–60%ofpatientspostopera-tively .TheriskforFrey’ssyndromecanbeminimizedfirstby complete and meticulous superficial parotidectomy .Second, by developing skin flaps of appropriate thick-ness,exposedapocrineglandsof theskinareprotectedfromingrowthandstimulationbytheseveredbranchesoftheauriculotemporalnerveandtheirparasympatheticstimulationduringmeals .Therearenumerousnonsurgi-calandsurgicaltreatmentsforpersistentFrey’ssyndromefollowing parotidectomy (see Chapter5, Treatment ofFrey’sSyndrome) .

Arterial Supply

Thebloodsupplytotheparotidglandis frombranchesof the external carotid artery, which courses superiorlyfromthecarotidbifurcationandparalleltothemandibleundertheposteriorbellyofthedigastricmuscle .Thear-tery then travels medial to the parotid gland and splitsinto two terminal branches . The superficial temporal artery runs superiorly from the superior portion of theparotidgland to thescalpwithin thesuperiorpretragalregion . The maxillary artery leaves the medial portionof theparotidand supplies the infratemporal fossaandthepterygopalatinefossa .Duringradicalparotidectomy,thisvesselmustbecontrolledespeciallywhenmarginalorsegmentalmandibulectomyisrequired .Thetransverse facial arterybranchesoffthesuperficialtemporalarteryandrunsanteriorlybetweenthezygomaandparotidducttosupply theparotidgland,parotidduct,andthemas-setermuscle[10] .

Fig. 1.2:Parasympatheticsupplytothemajorsalivaryglands

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Venous Drainage

The retromandibular vein, formed by the union of themaxillary vein and the superficial temporal vein, runsthrough the parotid gland just deep to the facial nerveto join the external jugular vein . There is substantialvariationinthesurgicalanatomyoftheretromandibularvein,whichmaybifurcateintoananteriorandposteriorbranch .Theanterior branchcanunitewiththeposteriorfacial vein, forming the common facial vein . The pos-terior facial vein lies immediately deep to the marginalmandibular branch of the facial nerve and is thereforeoftenusedasa landmarkfor identificationof thenervebranch,especiallyattheantegonialnotchofthemandiblewherethenervedipsinferiorly[3] .Theposterior branch of the retromandibular veinmaycombinewiththepost-auricularveinabovethesternocleidomastoidmuscleanddrainintotheexternaljugularvein .

Lymphatic Drainage

Contrarytothelymphaticdrainageoftheothersalivaryglands,thereisahighdensityoflymphnodeswithinandaroundtheparotidgland .Theparotidistheonlysalivaryglandwithtwonodallayers,bothofwhichdrainintothesuperficial and deep cervical lymph systems . Approxi-mately90%ofthenodesarelocatedinthesuperficiallayerbetweentheglandulartissueanditscapsule .Theparotidgland,externalauditorycanal,pinna,scalp,eyelids,andlacrimalglandsarealldrainedbythesesuperficialnodes .Thedeeplayerofnodesdrainsthegland,externalaudi-torycanal,middleear,nasopharynx,andsoftpalate[7] .

Parapharyngeal Space

Tumors of the deep parotid lobe often extend mediallyintotheparapharyngealspace(PPS) .Thisspacejustpos-teriortotheinfratemporalfossaisshapedlikeaninvertedpyramid .Thegreatercornuof thehyoidboneservesastheapexandthepetrousboneoftheskullbaseactsasthepyramidalbase .ThePPSisboundmediallybythelateral pharyngeal wall,whichconsistsofthesuperiorconstric-tor muscles, the buccopharyngeal fascia and the tensorvelipalatine .Theramusofthemandibleandthemedialpterygoidmusclemakeupthe lateralborder .Thepara-pharyngealspaceisborderedanteriorlybythepterygoidfascia and the pterygomandibular raphe . The posterior

borderislinedbythecarotidsheathandprevertebralfas-cia .

Alinefromthestyloidprocesstothemedialportionofthemedialpterygoidplatedividestheparapharyngealspace into two compartments . The prestyloid compart-mentcontainsthedeeplobeoftheparotidgland,minorsalivary glands, as well as neurovascular structures, in-cludingtheinternalmaxillaryartery,ascendingpharyn-gealartery,theinferioralveolarnerve,thelingualnerve,andtheauriculotemporalnerve .Thepoststyloid compart-mentcontainstheinternaljugularvein,carotidarteryandvagusnervewithinthecarotidsheath,aswellascranialnervesIX, X, XI, and XII and the cervical sympatheticchain . Neurogenic tumors or paragangliomas from thecervicalsympatheticsorcranialnervescanthusariseinthiscompartment[4] .

Submandibular Gland

Anatomy

Thesubmandibulargland(inoldertexts,thisglandwassometimesreferredtoas“thesubmaxillarygland”)isthesecond largest major salivary gland and weighs 7–16g(Fig .1 .3) .Theglandislocatedinthesubmandibular tri-angle,whichhasasuperiorboundaryformedbytheinfe-rioredgeofthemandibleandinferiorboundariesformedbytheanteriorandposteriorbelliesofthedigastricmus-cle .Alsolyingwithinthetrianglearethesubmandibularlymphnodes, facialarteryandvein,mylohyoidmuscle,andthelingual,hypoglossal,andmylohyoidnerves .Mostofthesubmandibularglandliesposterolateraltothemy-lohyoidmuscle .Duringneckdissectionorsubmandibu-larglandexcision,thismylohyoidmusclemustbegentlyretractedanteriorlytoexposethelingualnerveandsub-mandibularganglion .Often,smaller,tongue-likeprojec-tionsof thegland follow theduct, as it ascends towardtheoralcavity,deeptothemylohyoidmuscle[29] .How-ever,theseprojectionsshouldbedistinguishedfromthesublingual gland which lies superior to the mylohyloidmuscle .(Formoredetail,seeChapter21,ManagementofTumorsoftheSubmandibularandSublingualGlands .)

Fascia

Themiddlelayerofthedeepcervicalfasciaenclosesthesubmandibulargland .Thisfasciaisclinicallyrelevantbe-

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causethemarginalmandibularbranchofthefacialnerveissuperficialtoit,andcaremustbetakentopreservethenerveduringsurgeryinthesubmandibularregion .Thus,divisionofthesubmandibularglandfascia,whenonco-logically appropriate, is a reliablemethodofpreservingandprotectingthemarginalmandibularbranchofthefa-cialnerveduringneckdissectionand/orsubmandibularglandresection .

Wharton’s Duct

The submandibular gland has both mucous and serouscellsthatemptyintoductules,whichinturnemptyintothe submandibular duct . The duct exits anteriorly fromthesublingualaspectofthegland,coursingdeeptothelingualnerveandmedialtothesublingualgland .Iteven-tuallyformsWharton’sductbetweenthehyoglossusandmylohyoid muscles on the genioglossus muscle . Whar-ton’sduct,themainexcretoryductofthesubmandibulargland,isapproximately4–5cmlong,runningsuperiortothehypoglossalnervewhileinferiortothelingualnerve .Itemptieslateraltothelingualfrenulumthroughapapillainthefloorofthemouthbehindthelowerincisortooth .Theopeningsforthesublingualgland,orthesublingual caruncles,arelocatednearthemidlineofthesublingualfoldintheventraltongue .

Neural Anatomy

Both the submandibular and the sublingual glands areinnervatedbythesecretomotorfibersofthefacialnerve(CNVII) .Parasympatheticinnervationfromthesuperior salivatory nucleus in the pons passes through the ner-vus intermediusand into the internalauditorycanal tojointhefacialnerve .Thefibersarenextconveyedbythechorda tympani nerveinthemastoidsegmentofCNVII,whichtravelsthroughthemiddleearandpetrotympanicfissure to the infratemporal fossa . The lingual nerve, abranchof themarginalmandibulardivisionof thefifthcranialnerve(CNV),thencarriesthepresynapticfibersto the submandibular ganglion . The postsynaptic nerveleavesthegangliontoinnervateboththesubmandibularandsublingualglandstosecretewaterysaliva .Asintheparotidgland,sympatheticinnervationfromthesuperior cervical ganglion accompanies the lingual artery to thesubmandibulartissueandcausesglandularproductionofmucoidsalivainstead[5] .

The lingual nervebranchesoffthemandibulardivi-sion of the trigeminalnerve (V3) in the infratemporalfossatosupplygeneralsensationandtastetotheante-riortwothirdsofthetongue .Thenervecourseslaterallybetweenthemedialpterygoidmuscleandramusofthemandible and enters the oral cavity at the lower thirdmolar to then travel across the hyoglossus along the

Fig. 1.3:Thesubmandibularglandandimportantanatomiclandmarks

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floorofthemouthinasubmucosalplane .Beneaththemandible, a small motor nerve branches off and trav-els posteriorly from the lingual nerve to innervate themylohyoid muscle . These fibers are usually sacrificedduring surgical removal of the submandibular gland .Parasympatheticfibersarecarriedviathelingualnervetothesubmandibularganglion,andpostsynapticfibersexitalongthecourseofthesubmandibularducttoin-nervatethegland .

Thehypoglossalnerve(CNXII)suppliesmotorinner-vationtoallextrinsicandintrinsicmusclesofthetongueexceptforthepalatoglossusmuscle .Fromthehypoglos-salcanalatthebaseoftheskull, thenerveispulledin-feriorly during embryonic development down into theneck by the occipital branch of the external carotid ar-tery .Fromhere,thehypoglossalnervetravelsjustdeeptotheposteriorbellyofthedigastricmuscleandcommontendonuntilitreachesthesubmandibulartriangle .HereCNXIIliesdeepinthetrianglecoveredbyathinlayeroffascia .Itslocationisanterior,deepandmedialrelativetothesubmandibulargland .Typicallythenervehasacloserelationshiptotheanteriorbellyofthedigastricmuscle .Itthenascendsanteriortothelingualnerveanditsgenudeep to the mylohyoid muscle . Extreme care should betakentopreservethisimportantnerveduringheadandnecksurgery .

Arterial Supply

Boththesubmandibularandsublingualglandsaresup-pliedbythesubmentaland sublingual arteries,branchesofthelingualandfacialarteries .Thefacial artery,thetor-tuousbranchof theexternal carotidartery, is themainarterialbloodsupplyofthesubmandibulargland .Itrunsmedialtotheposteriorbellyofthedigastricmuscleandthenhooksovertocoursesuperiorlydeeptothegland .Thearteryexitsatthesuperiorborderoftheglandandthe inferior aspect of the mandible known as the facial notch .Itthenrunssuperiorlyandadjacenttotheinferiorbranches of the facial nerve into the face . During sub-mandibularglandresection,thearterymustbesacrificedtwice, first at the inferior border of the mandible andagainjustsuperiortotheposteriorbellyofthedigastricmuscle .Thelingual arterybranchesinferiortoorwiththefacialarteryofftheexternalcarotidartery . Itrunsdeepto the digastric muscle along the lateral surface of themiddleconstrictorandthencoursesanteriorandmedialtothehyoglossusmuscle .

Venous Drainage

The submandibular gland is mainly drained by the an-terior facial vein,whichisincloseapproximationtothefacialarteryasitrunsinferiorlyandposteriorlyfromthefacetotheinferioraspectofthemandible .Becauseitliesjustdeeptothemarginalmandibulardivisionofthefacialnerve,ligationandsuperiorretractionoftheanteriorfa-cialveincanhelppreservethisbranchofthefacialnerveduringsubmandibularglandsurgery . It formsextensiveanastomoseswiththeinfraorbitalandsuperiorophthal-micveins .Thecommon facial veinisformedbytheunionoftheanteriorandposteriorfacialveinsoverthemiddleaspectofthegland .Thecommonfacialveinthencourseslateraltotheglandandexitsthesubmandibulartriangletojointheinternaljugularvein .

Lymphatic Drainage

Theprevascularandpostvascularlymphnodesdrainingthesubmandibularglandare locatedbetweentheglandanditsfascia,butarenotembeddedintheglandulartis-sue .They lie incloseapproximation to the facialarteryandveinat the superioraspectof theglandandemptyintothedeepcervicalandjugularchains .Thesenodesarefrequentlyassociatedwithcancersintheoralcavity,es-peciallyinthebuccalmucosaandthefloorofthemouth .Thus, when ligating the facial artery and its associatedplexusofveins,greatercaremustbetakennotonlytore-sectallassociatedlymphoadiposetissue,butalsotopre-servethemarginalmandibularbranchofthefacialnerve,whichrunsincloseproximitytothesestructures .

Sublingual Gland

Thesmallestofthemajorsalivaryglandsisthesublingualgland,weighing2–4g .Consistingmainlyofmucousaci-narcells,itliesasaflatstructureinasubmucosalplanewithintheanteriorfloorofthemouth,superiortothemy-lohyoidmuscleanddeeptothesublingualfoldsoppositethelingualfrenulum[11] .Lateraltoitarethemandibleandgenioglossusmuscle .Thereisnotruefascialcapsulesurroundingthegland,whichisinsteadcoveredbyoralmucosaonitssuperioraspect .Severalducts(of Rivinus)fromthesuperiorportionofthesublingualglandeithersecrete directly into the floor of mouth, or empty intoBartholin’s ductthatthencontinuesintoWharton’sduct .

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F. Christopher Holsinger and Dana T. Bui

Both the sympathetic and parasympathetic nervoussystemsinnervatethesublingualgland .Thepresynapticparasympathetic(secretomotor)fibersofthefacial nervearecarriedbythechordatympaninervetosynapseinthesubmandibularganglion .Postganglionicfibersthenexitthesubmandibular ganglionandjointhelingualnervetosupply the sublingual gland . Sympathetic nerves inner-vatingtheglandtravelfromthecervical ganglionwiththefacialartery[5] .

Bloodissuppliedtothesublingualglandbythesub-mental and sublingual arteries,branchesofthelingualandfacialarteries,respectively .Thevenousdrainageparallelsthecorrespondingarterialsupply .Thesublingualglandismainlydrainedbythesubmandibularlymphnodes .

Ranulasarecystsormucocelesofthesublingualgland,and they can exist either simply within the sublingualspace or plunging posteriorly to the mylohyoid muscleintotheneck .Asimpleranulawillmostcommonlypres-entasabluish,nontendermassinthefloorofthemouthand may either be a retention cyst or an extravasationpseudocyst . A plunging ranula will present as a soft,painless cervical mass and is always an extravasationpseudocyst (see Chapter10, Management of MucoceleandRanula) .

Minor Salivary Glands

About 600 to 1,000 minor salivary glands, ranging insize from 1 to 5mm, line the oral cavity and orophar-ynx .Thegreatestnumberoftheseglandsareinthelips,tongue, buccal mucosa, and palate, although they canalsobefoundalongthetonsils,supraglottis,andparana-salsinuses .Eachglandhasasingleductwhichsecretes,directlyintotheoralcavity,salivawhichcanbeeitherse-rous,mucous,ormixed .

Postganglionic parasympathetic innervation arisesmainlyfromthelingual nerve .Thepalatinenerves,how-ever, exit the sphenopalatine ganglion to innervate thesuperiorpalatalglands .Theoralcavityregionitselfdeter-minesthebloodsupplyandvenousandlymphaticdrain-ageoftheglands .Anyofthesesitescanalsobethesourceofglandulartumors[11] .

Histology

Allglandsingeneralarederivedfromepithelialcellsandconsistofparenchyma(thesecretoryunitandassociated

ducts)andstroma(thesurroundingconnectivetissuethatpenetratesanddividestheglandintolobules) .Secretoryproductsaresynthesizedintracellularlyandsubsequentlyreleasedfromsecretorygranulesbyvariousmechanisms .Glandsareusuallyclassifiedintotwomaingroups .Endo-crine glandscontainnoducts,andthesecretoryproductsare released directly into the bloodstream or lymphaticsystem .Incontrast,exocrine glandssecretetheirproductsthroughaductsystemthatconnectsthemtotheadjacentexternalorinternalepithelialsurfaces .Salivaryglandsareclassified as exocrine glands that secrete saliva throughducts from a flask-like, blind-ended secretory structurecalledthe salivary acinus.

Theacinusitselfcanbedividedintothreemaintypes .Serous aciniinsalivaryglandsareroughlysphericalandrelease via exocytosis a watery protein secretion that isminimally glycosylated or nonglycosylated from secre-tory(orzymogen)granules .Theacinarcellscomprisingtheacinusarepyramidal,withbasallylocatednucleisur-roundedbydensecytoplasmandsecretorygranulesthataremostabundantintheapex .Mucinous acinistoreavis-cous,slimyglycoprotein(mucin)withinsecretorygran-ulesthatbecomehydratedwhenreleasedtoformmucus .Mucinous acinar cells are commonly simple columnarcellswithflattened,basallysituatednucleiandwater-solu-blegranulesthatmaketheintracellularcytoplasmappearclear .Mixed,orseromucous,acinicontaincomponentsofbothtypes,butonetypeofsecretoryunitmaydominate .Mixedsecretoryunitsarecommonlyobservedasserousdemilunes(orhalf-moons)cappingmucinousacini .

Between the epithelial cells and basal lamina of theacinus,flatmyoepithelial cells(orbasketcells)formalat-ticeworkandpossesscytoplasmicfilamentsontheirbasalside toaid incontraction,and thus forcedsecretion,oftheacinus .Myoepithelialcellsarealsoobservedaroundintercalatedducts,butheretheyaremorespindleshaped[16] .

Electrolyte modification and transportation of salivaarecarriedoutbythedifferentsegmentsofthesalivarygland’s duct system (Fig .1 .4) . The acini first secretethrough small canaliculi into the intercalated ducts,whichinturnemptyintostriatedductswithintheglan-dularlobule .Theintercalatedductiscomprisedofanir-regularmyoepithelial cell layer linedwith squamousorlow cuboidal epithelium . Bicarbonate is secreted intowhilechlorideisabsorbedfromtheacinarproductwithintheintercalatedductsegment .Striatedductshavedistin-guishingbasalstriationsduetomembraneinvaginationand mitochondria and are lined by a simple columnar

�Anatomy, Function, and Evaluation Chapter 1

epithelium .Theseductsareinvolvedwiththereabsorp-tionofsodiumfromtheprimarysecretionandthecon-comitant secretion of potassium into the product . Theabundantpresenceofmitochondria isnecessaryfortheducts’ transportofbothwaterandelectrolytes .Theaci-nus, intercalated duct, and striated duct are collectivelyknownasasinglesecretoryunitcalledasalivon [15] .

Thenextsegmentoftheductsystemismarkedbytheappearanceoftheinterlobularexcretoryductswithintheconnective tissueof theglandular septae .Theepitheliallining is comprised of sparse goblet cells interspersedamongthepseudostratifiedcolumnarcells .Asthediam-eteroftheductincreases,thecompositionoftheepithe-lialliningtransitionstostratifiedcolumnar,andthentononkeratinizedstratifiedsquamouscells,withintheoralcavity[16] .

Thearterialbloodflowreceivedbythesalivaryglandsis high relative to their weight and is opposite the flowofsalivawithintheductsystem .Theaciniandductulesaresuppliedbyseparateparallelcapillarybeds .Thehighpermeability of these vessels permits rapid transfer ofmolecules across their basement membranes . The highvolumeofsalivaproducedbythesalivaryglandsrelativetotheirweightispartlyduetothehighbloodflowratethroughtheglandulartissue .

The serous acini that make up the parotid gland areroughlyspherical,andtheyarecomprisedofpyramidalepithelialcellssurroundedbyadistinctbasementmem-brane .Merocrinesecretionbytheepithelialcellsreleasesa secretory mixture containing amylase, lysozyme, anIgA secretory piece, and lactoferrin into the central lu-menoftheacinus .ThemainexcretoryductisalsoknownasStensen’s ductandemptiesintotheoralcavityoppositetheseconduppermolartooth .

Thesubmandibular glandisclassifiedasamixedglandthatispredominantlyserouswithtubularacini .Thema-jorityofacinarcellsareserouswithverygranulareosino-philiccytoplasm .Onlyapproximately10%oftheaciniaremucinous, with large, triangular acinar cells containingcentralnucleiandclearcytoplasmicmucinvacuolesrang-inginsize .Themucinouscellsarecappedbydemilunes,whicharecrescent-shapedformationsofserouscells .Theintercalatedductsofthesubmandibularglandarelongerthanthoseoftheparotidgland,whilestriatedductsareshorterbycomparison .Wharton’s ductservesasthemainexcretoryductandemptiesintothefloorofthemouth .

Like the submandibular gland, the sublingual glandhas mixed acini with observable serous demiluneswithin the glandular tissue . Unlike the submandibulargland, however, the sublingual gland is predominantly

Fig. 1.4:Functionalhistologyofthesalivon

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F. Christopher Holsinger and Dana T. Bui

mucinous .Themainductemptiesintothesubmandib-ularductandisalsoknownasBartholin’s duct .Severalsmaller ducts (of Rivinus) also directly secrete into thefloorofthemouth .

The minor salivary glands are found throughout theoralcavity,withthegreatestdensityinthebuccalandla-bialmucosa,theposteriorhardpalate,andtonguebase .Theyarenotasoftenobserved,however,intheattachedgingivaandcloselyassociatedanteriorhardpalatalmu-cosa .Themajorityoftheseglandsareeithermucinousorseromucinous,exceptfortheserousEbner’s glandsontheposterioraspectofthetongue .Thesedeepposteriorsali-varyglandsofthetonguearealsomarkedbythepresenceofciliatedcells, especiallywithin thedistal segmentsoftheexcretoryducts .Theminorsalivaryglandductsystemissimpler thanthatof themajorsalivaryglands,wheretheintercalatedductsarelongerandthestriatedductsareeitherlessdevelopedornotpresent[15] .

Physiology of Salivary Glands

Saliva production, the main function of the salivaryglands, is crucial in the processes of digestion, lubrica-tion, and protection in the body . Saliva is actively pro-ducedinhighvolumesrelativetothemassofthesalivaryglands,anditisalmostcompletelycontrolledextrinsicallybyboththeparasympatheticandsympatheticdivisionsoftheautonomicnervoussystem .

Salivaplaysacrucialroleinthedigestionofcarbohy-dratesandfatsthroughtwomainenzymes .Ptyalinisanα-amylaseinsalivathatcleavestheinternalα-1,4-glyco-sidicbondsofstarchestoyieldmaltose,maltotriose,andα-limitdextrins .ThisenzymefunctionsatanoptimalpHof 7, but rapidly denatures when exposed to a pH lessthan4,suchaswhenincontactwiththeacidicsecretionsofthestomach .Upto75%ofthecarbohydratecontentinameal,however, isbrokendownbytheenzymewithinthestomach .Thisisduetothefactthatasignificantpor-tionofaningestedmealremainsunmixedwithintheoralregion,andthusthereisadelayinthemixtureofgastricjuiceswiththefoodbolus .Starchdigestionisnotslowedin the absence of ptyalin because pancreatic amylase isidentical to salivary amylase and is thus able to breakdownallcarbohydrateswheninthesmallintestine .Thesalivaryglandsofthetongueproducelingual lipase,whichfunctionstobreakdowntriglycerides .Unlikeptyalin,thisenzymeisfunctionalwithintheacidicstomachandprox-imalduodenumbecauseitisoptimallyactiveatalowpH .

Salivaalsoservestodissolveandtransportfoodparticlesawayfromtastebudstoincreasetastesensitivity .

Themucusconstituentofsalivafacilitatesthelubrica-tion of food particles during the act of chewing, whichservestomixthefoodwithsaliva .Lubricationeasestheprocessesofswallowingandofthebolustravelingdownthe esophagus . Salivary lubrication is also crucial forspeech .

The antibacterial properties of saliva are due to itsmany protective organic constituents . The binding gly-coprotein for immunoglobulinA (IgA), known as thesecretory piece,formsacomplexwithIgAthatisimmu-nologicallyactiveagainstvirusesandbacteria .Lysozymecauses bacterial agglutination and autolysin activationto degrade bacterial cell walls . Lactoferrin inhibits thegrowthofbacteria thatneed ironbychelatingwith theelement .Salivaalsoservesasaprotectivebuffer for themouthbydilutingharmfulsubstancesandloweringthetemperatureof solutions thatare toohot . Itwashesoutfoul-tasting substances from themouthandneutralizesgastricjuicetoprotecttheoralcavityandesophagus .Xe-rostomia,ordrymouth,duetolackofsalivation,canleadtochronicbuccalmucosalinfectionsordentalcaries .

Comprisedofbothinorganicandorganiccompounds,saliva is distinguished by its high volume compared tosalivaryglandweight,highpotassiumconcentration,andlow osmolarity (Fig .1 .5) . The large relative volume ofsalivaproductionisduetoitshighsecretionrate,whichcangoupto1mlpergramofsalivaryglandperminute .Saliva ismostlyhypotonic toplasma,but itsosmolarityincreaseswithincreasingrateofsecretion,andatitshigh-estratesalivaapproaches isotonicity .Theconcentrationofelectrolytesinsalivaalsochangeswithvaryingsecre-tionrates .

Withinthesalivarygland,potassium(K+)concentra-tionisalwayshighwhilesodium(Na+)concentrationislowcomparedtothatfoundinplasma .Withincreasingflow rates, however, Na+ concentration increases, whileK+concentrationinitiallydecreasesslightlyandthenlev-elsofftoaconstantlevel .Chloride(Cl−)concentrationsfollowthesamegeneralpatternasNa+concentrations .Inotherwords,Na+andCl−aregenerallysecretedandthenslowlyreabsorbedalongthecourseofthesalivarysystem,fromacinustoduct .Thesalivaryconcentrationofbicar-bonate(HCO3−)ishypertoniccomparedtoinplasmaex-ceptatlowerratesofsecretion .

Initially within the salivon, the acini first produce aprimary secretion that is relatively isotonic to plasma .As the saliva travels through theducts,Na+andCl−are

11Anatomy, Function, and Evaluation Chapter 1

reabsorbed, while K+ and HCO3− are secreted into thefluid . Less time is available for the movement of theseelectrolyteswhentheflowrateofsalivaishigher .Athighflowrates,therefore,plasmaandsalivaaresimilarincon-centration .At lowersecretionrates,K+concentrationishigher in the saliva, while Na+ and Cl− concentrationsaresignificantlylower .Bicarbonateconcentratesremainsfairlyhypertonic relative to inplasmaevenwithhigherflowratesdue to its secretory stimulationbymost sali-varyglandagonists .SalivaismostlyhypotonictoplasmaduetothefactthatreabsorptionofNa+andCl−isgreaterthan the secretionofK+andHCO3−within the salivaryducts .

Severalorganiccompoundspresentinsalivahaveal-ready been discussed: α-amylase, lingual lipase, mucus,lysozymes,glycoproteins,lactoferrin,andtheIgAsecre-torypiece .Salivaisalsocomprisedoftheorganicblood group antigensA,B,AB,andO .Kallikreinissecretedbythe salivary glands during increased metabolic activity .

Kallikrein enzymatically converts plasma protein intobradykinin,avasodilator,inordertoincreasebloodflowtotheglands .Salivacontainsapproximatelyonetenththetotalamountofproteinasthatfoundinplasma .

Thesecretion,bloodflow,andgrowthofsalivaryglandsaremostlycontrolledbybothbranchesoftheautonomicnervous system . Even though the parasympathetic ner-voussystemhasmoreinfluenceonthesecretionrateofthe salivary glands than the sympathetic system, secre-tionisstimulatedbybothbranches .

Parasympathetic innervation of the major salivaryglands followsbranchesof the facialandglossopharyn-geal nerves . Parasympathetic stimulation activates bothacinar activity and ductal transport mechanisms, lead-ingtoglandularvasodilationaswellasmyoepithelialcellcontraction .Acetylcholine(ACh)servesastheparasym-patheticneurotransmitterthatactsonthemuscarinicre-ceptorsofthesalivaryglands .ThesubsequentformationofinositoltrisphosphateleadstoincreasedCa2+concen-

Fig. 1.5:Electrolytesecretionbytheacinarandductalcells

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F. Christopher Holsinger and Dana T. Bui

trationswithinthecell,releasedfromeitherintracellularCa2+ stores or from the plasma . This second messengersignificantly effects salivary volume secretion . Glandu-lar secretion is sustained byacetylcholinesterases, whichinhibit the breakdown of ACh . The muscarinic antago-nistatropine,however,decreasessalivationbycompetingwithAChforthesalivaryreceptorsite .

Thesympatheticsupplytothesalivaryglandismainlyfromthe thoracic spinalnervesof the superiorcervicalganglion .Likeparasympatheticinnervation,myoepithe-lial cell contractionalso results .Changes inbloodflow,however,arebiphasic:vasoconstrictiondue toα-adren-ergicreceptoractivationisfollowedbyvasodilationdueto buildup of vasodilator metabolites . Binding of theneurotransmitter norepinephrine to α-adrenergic recep-tor results in formationof3',5'-cyclic adenosinemono-phosphate(cAMP),whichthenleadstophosphorylationofvariousproteinsandactivationofdifferent enzymes .Increases in cAMP result in increased salivary enzymeandmucuscontent .

Within saliva, K+ concentrations increase while Na+concentrations decrease in the presence of antidiuretichormone (ADH) or aldosterone . Unlike other digestiveglands,however,thesetwohormonesdonotaffectsali-varyglandsecretionrate .

About1lofsalivaissecretedbyanormaladulteachday .Duringunstimulatedsalivation,69%ofsalivaiscon-tributedbythesubmandibularglands,26%bytheparotid,and 5% by the sublingual glands . The relative amountssuppliedbytheparotidandsubmandibularglands,how-ever,are switchedduringstimulation,where two thirdsofsecretionisthenfromtheparotidgland .Oftotalflow,7–8% is due to the minor salivary glands regardless ofstimulation .Thepresenceoffoodinthemouth,theactofchewing,andnauseaallstimulatesalivation,whilesleep,fatigue,dehydration,andfearinhibitit .Salivarysecretionrates are not dependent on age, and flow rates remainconstantdespite thedegenerationofacinarcellsduringtheagingprocess .Medicationsideeffectsorsystemicdis-easearemorelikelytoberesponsibleforhypofunctionofsalivaryglandsinelderlypatients[15,17] .

Evaluation of the Salivary Glands

Symptomsindicativeofsalivaryglanddisordersarelim-ited innumberandgenerallynonspecific .Patientsusu-ally complain of swelling, pain, xerostomia, foul taste,andsometimessialorrhea,orexcessivesalivation .Despite

theprevalenceofmoderntechnologyintheidentificationof salivaryglanddisorders,adetailedhistoryand thor-ough physical examination still play significant roles intheclinicaldiagnosisofthepatient,andgreatcareshouldbetakenduringtheseinitialstepsofevaluation .

History

When taking a patient’s history, the practiced skills ofattentive listening and patience are required for subse-quentdiagnosisandpropertreatmentmostfittingtothepatient’s expectationsandneeds .Themedicalprofileofthepatientcanprovidehelpfulcluestothecurrentcondi-tionofthesalivaryglands,fordysfunctionoftheseglandsisoftenassociatedwithcertainsystemicdisorderssuchasdiabetesmellitus,arteriosclerosis,hormonalimbalances,andneurologicdisorders .Eitherxerostomiaorsialorrhea,forinstance,maybeduetofactorsaffectingthemedul-larysalivarycenter,autonomicoutflowpathway,salivaryglandfunctionitself,orfluidandelectrolytebalance .

Thefactorsofagegroupandgenderarealso impor-tant,forseveraldiseasesareoftenrelatedtoageorgender .TheautoimmunedisorderknownasSjögren’s syndrome,for example, is common in menopausal women, whilemumps, parotid swelling due to paramyxoviral infec-tion,usuallyoccursinchildrenbetweentheagesof4and10years .

Drughistoryofthepatientshouldalsobeconsidered,forsalivaryfunctionisoftenaffectedbydrugusage .Xe-rostomiaisoftenduetotheuseofdiureticsandotheran-tihypertensivedrugs[9,18] .

Acarefuldietaryandnutritionhistoryshouldbeob-tained .Patientswhoaredehydratedchronicallyfrombu-limiaoranorexiaorduringchemotherapyareatriskforparotitis .Swellingandpainduringmeals followedbyareduction insymptomsaftermealsmay indicatepartialductalstenosis .

Xerostomiaisadebilitatingconsequenceofradiationtherapytotheheadandneckandahistoryofpriorradia-tionshouldbesought .

Physical Examination

Thesuperficiallocationofthesalivaryglandsallowsthor-ough inspection and palpation for a complete physicalexamination . Initial inspection involves the careful ex-aminationoftheheadandneckregions,bothintraorally

1�Anatomy, Function, and Evaluation Chapter 1

andextraorally,andshouldbecarriedoutinasystematicwaysoastonotmissanycrucialsigns .

During the initial extraoral inspection, the patientshouldstandthreetofourfeetawayanddirectlyfacingin front of the examiner . The examiner should inspectsymmetry,color,possiblepulsationanddischargingofsi-nusesonbothsidesofthepatient .Enlargementofmajororminorsalivaryglands,mostcommonlytheparotidorsubmandibular,mayoccurononeorbothsides .Parotitistypicallypresentsaspreauricularswelling,butmaynotbevisibleifdeepintheparotidtailorwithinthesubstanceofthegland .Submandibularswellingpresentsjustmedialandinferiortotheangleofthemandible .Salivaryglandswellingcangenerallybedifferentiatedfromthoseoflym-phaticoriginasbeingsingle,larger,andsmoother,butthetwotypesareofteneasilyconfused .Significantneurologicdeficitsshouldbeexaminedaswell .Facialnerveparalysisinconjunctionwithaparotidmass,forexample,shouldremindusofamalignantparotidneoplasm,althoughitdoesoccurrarelywithbenignneoplasmsaswell .

Inadditiontosignsofpossibleasymmetry,discolor-ation,orpulsation,intraoral inspectionalsoincludesas-sessment of the duct orifices and possible obstructions .The proper lighting with a headlight should always beusedwheninspectingwithintheoralcavityandpharynx .TheopeningsofStensen’sandWharton’sductscanbein-spectedintraorallyoppositetheseconduppermolarandattherootofthetongue,respectively .Dryingoffthemu-cosaaroundtheductswithanairblowerandthenpress-ingonthecorrespondingglandswillallowtheexaminertoassess theflowor lackofflowof saliva .Sialolithiasiscan sometimes be found by careful intraoral palpation .Dentalhygieneand thepresenceofperiodontaldiseaseshouldalsobenotedsincedeficientoralmaintenanceisamajorpredisposingfactortovariousinfectiousdiseases .

Size, consistency, and other qualities of the salivaryglandsandassociatedmasses canbeevaluated throughextraoral and intraoral palpation . Bimanual assessmentshouldbeperformedwheneverpossiblewiththepalmaraspectofthefingertips .

Duringextraoral palpation of the face and neck, thepatient’sheadisinclinedforwardtomaximallyexposetheparotidandsubmandibularglandregions .Theexaminermaystandinfrontoforbehindthepatient .Itshouldbenotedthatobservablesalivaryorlymphaticglandswell-ingsdonotrisewithswallowing,whileswellingsassoci-atedwiththethyroidglandandlarynxdoelevate .

Finally,bimanualpalpation(extraoralwithonehand,introral with the other) must be performed to exam-

ine the parotid and submandibular glands . One or twoglovedfingers shouldbe insertedwithin theoral cavitytopalpatetheglandsandmainexcretoryductsinternally,whileusingtheotherhandtoexternallysupporttheheadandneck .Byrollingthehandsovertheglandsbothinter-nallyandexternally,subtlemasslesionscanbeidentified .Inthesubmandibulargland,lymphnodesextrinsictotheglandcanoftenbedistinguishedfrompathologywithinthe gland itself using this technique . The neck shouldthenalsobecarefullyexaminedforlymphadenopathy .

Finally, a careful survey of minor salivary gland tis-sueshouldbeperformed,especiallyintheanteriorlabial,buccal,andposteriorpalatalmucosa .Increasedsalivationfromtheductorificesduetopressureexternallyappliedtotheglandsmayindicateinflammation[9,18] .Finally,rareclinicalentities,suchashemangiomasandothervas-cularanomalies,maybeidentifiedbyauscultation .

Radiologic and Endoscopic Examination of the Salivary Glands

Althoughathoroughhistoryandcompletephysicalex-amination are crucial steps in the diagnosis and even-tual treatment of any salivary gland disorder, patientsoccasionally provide little more than vague complaintsofpainand/orswelling .Forpatientswiththeseunclearsymptomsandnophysicalsigns,radiographicdiagnosticstudies,suchassialography,plain-filmradiography,com-putedtomography,andmagneticresonanceimaging,canplay in importantrole inclarifyingtheetiologyofsuchnonspecificsymptoms .Forpatientswithknowndisease,imagingcanassist in treatment selectionandplanning .This final section will provide a brief introduction tothesevarioustechniques,whichwill thenbecoveredingreaterdetailinsubsequentchapters .

Sialographyreliesontheinjectionofcontrastmediumintoglandularductssothatthepathwayofsalivaryflowcanbevisualizedbyplain-filmradiographs .Correctex-posureandpositioningisachievedbytakingpreliminaryplainradiographspriortotheinjectionofaradiopaquemedium[9] .Themostcommonindicationforsialogra-phyisthepresenceofasalivarycalculus,whichisade-posit of mostly calcium salts that can block flow of sa-livaandcausepain, swelling,and inflammationor leadto infection .Patientswithcalculiusuallycomplainofarecurrent and acute onset of pain and swelling duringeating .Often,sialographicexaminationisunnecessaryifthe preliminary radiographs detect the calculus before-

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F. Christopher Holsinger and Dana T. Bui

hand .Otherindicationsforsialographyincludegradualorchronicglandularenlargement(whichcanbeduetosarcoidosis, infection, sialosis, Sjögren’s syndrome, be-nignlymphoepitheliallesion,oraneoplasm),aclinicallypalpablemass inoneof theglandular regions (possibletumor,cyst,orfocalinflammation),recurrentsialadeni-tis,ordrynessofthemouth .

Although conventional sialography can be clinicallyuseful in the diagnosis and the determination of treat-ment for various salivary disorders, its effectiveness re-mainsarguablewhile itsrateofusage ishighlyvariable[25,30] .Thismethodshouldnotbeperformedwhenthepatienthasanacutesalivaryglandinfection,hasaknownsensitivity to iodine-containing compounds, or is an-ticipatingthyroidfunctiontests .Thus,othermethodsofradiographicdiagnosisarecurrentlypreferredandhavelargelyreplacedsialographicexamination .

Computedtomography(CT)isnowmorewidelyusedtoassesstheparotidandsubmandibularglands .Thead-vantageofCTimagingisthetwo-dimensionalviewofthesalivaryglands,whichcanelucidaterelationshipstoadja-centvitalstructuresaswellastoassessthedrainingcervi-callymphatics .TheparotidglandhaslowattenuationduetoitshighfatcontentandisthereforeeasilydiscerniblebyCTscanning .Thesubmandibularglandhasalowerfatcontentandhigherdensitycomparedtotheparotidglandandthushasamuchhigherattenuation,althoughextrin-sicandintrinsicmassdifferentiationiseasiertoevaluate .Althoughstonescanbeidentified,salivaryglandinflam-mationisnotgenerallyanindicationforCT .WhileCTisoftenutilizedasaprimaryscreeningtoolforthedetec-tionofparotidandsubmandibularglandabnormalities,indifficultcases,ahigher-sensitivityapproachusingbothCTandsialography (CT-sialography)canbeused [24] .Differencesbetweenintrinsicandextrinsicparotidglandmasses, however, are often difficult to assess especiallywhenpresentintheparapharyngealspace[27] .

Magneticresonanceimaging(MRI)ismoreoftenusedfor assessment of parapharyngeal space abnormalities .MRIprovidesbettercontrast resolution,exposes thepa-tienttolessharmfulradiation,andyieldsdetailedimagesonseveraldifferentplaneswithoutpatientrepositioning .Thistechniquethereforeispreferredintheevaluationofparapharyngealspacemasses,especiallyindiscriminatingbetween deep lobe parotid tumors and other pathology,suchasschwannomaand/orglomusvagale .MRI,however,isinferiortoCTscanningforthedetectionofcalcificationsandearlyboneerosion .Chronicinflammationofthesali-varyglandsandcalculiarenotindicationsforMRI .

Sialendoscopyisaminimallyinvasivetechniquethatinspectsthesalivaryglandsusingnarrow-diameter,rigidfiberoptic endoscopes [20] . Endoscopic visualization ofductalandglandularpathologyprovidesanexcellental-ternativetotheindirectdiagnostictechniquesdescribedabove .Assuch,sialendoscopyhasopenedupanewfron-tier forbothevaluationandtreatmentof salivaryglanddisease[21] .Lacrimalprobesareusedtogentlydilatetheductalorificeandthentheendoscopeisintroducedun-der direct visualization . During lavage of the glandularductofinterest,directinspectionoftheductandhilumoftheglandisperformed .Thus,inonesetting,atthetimeofdiagnosis, treatmentandtherapyforbenignlesionscanbe performed (see Chapter6, Sialendoscopy) . Througha CO2-laser papillotomy, sialolithectomy can be easilyperformed[21] .Pharmacotherapyandlaser-ablationcanalsobeperformed .Sialendoscopyhasalsobeenshowntohavea significantly lowcomplicationrateand isgener-allywell-tolerated[31] .Thisrelativelynewtechniquehasshownmuchpromiseinthediagnosisandtreatmentofchronicobstructivesialadenitis(COS),sialolithiasis,andotherobstructivediseasesofthesalivaryglands .

    Take Home Messages

→ Salivary gland development is the result ofbranching morphogenesis . Molecular biologyis beginning to unravel signaling pathways im-plicated in both craniofacial development andsalivary gland histogenesis, including the sonichedgehog(Shh)andthefibroblastgrowthfactorfamily .

→ Humansalivaisnotonlyimportantforlubrica-tionintheoralcavity,butplaysacrucialroleindigestiveandprotectiveprocesses .

→ Bothvisualinspectionwithoptimallightingandbimanualpalpationiscrucialintheprecisephys-icalexaminationofthemajorandminorsalivaryglands .

→ Sialendoscopyisanovelmodalityfordiagnosticevaluationaswellastherapeuticinterventionfordisordersofthesalivaryglands .

1�Anatomy, Function, and Evaluation Chapter 1

References

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F. Christopher Holsinger and Dana T. Bui