1. • SALIVA & SALIVARY GLANDS
• INTRODUCTION
The mouth isthe gatewayfor foodanddrinkdestinedforthe gastro-intestinal tract.SALIVARY
Glandsecretionsperformaconsiderablenumberof protective functionsdue totheircomplex
physical andchemical composition.
SALIVA isa unique defensive systempresentinthe mouthwhichhelpstoensure the integrityof
the Oral Tissues.
Definition
SALIVA: It isa wateryfilm/liquidproducedbyglandsinthe mouthcomprisingof organicand inorganic
constituentswhichhelpsinchewing,swallowinganddigestion.( Tencate’s)
It isa clear liquidsecretedintothe mouthbysalivaryglandsandmucousglandsof the mouth;it
moistensthe mouthandstartsthe digestionof starches( WEBSTER’SDictionary)
J About90% of total SalivaryflowisfromParotidAndSubmaxillaryGlands,5% fromSublingual
Glandsand 5% from MinorSalivaryGland
J DailySecretionof Salivarangesbetween500and 1500 mls.
J Normal stimulatedsecretionrate inadultsis1-2 ml/min
J Salivaconstitutesone of the largestsecretionsof the humanbody
J As salivaissecretedbysalivaryglandswe needtofirsttodiscussthe salivaryglands.
• Overviewof Salivary Glands
• CLASSIFICATIONOF SALIVARY GLANDS
SALIVARYGLANDS
MAJOR SALIVARY GLANDS
LOCATED OUTSIDE THE ORAL
CAVITY WITH EXTENDED DUCT
SYSTEM THROUGH WHICHTHE GLAND
SECRETIONS REACH THE MOUTH.
MINOR SALIVARY GLANDS
2. LOCATED IN THE SUBMUCOSAL
LAYER WITH SHORT DUCTS
OPENING DIRECTLY ONTO THE
MUCOSALSURFACE.
• DEVELOPMENT OF SALIVARY GLANDS
• The salivaryglandsdevelopasoutgrowthsof the buccal epithelium.
• Duringfetal life eachsalivaryglandisformedata specificlocationinthe oral cavitythroughthe
growthof a bud of oral epitheliumintothe underlyingmesenchyme.
• The promodiaof the parotidand submandibularglandsof humansappearduring6th
weekand
that of sublingual glandappearafter7th
week.The minorsalivaryglandsbegintheir
developmentduringthirdmonth.
These outgrowthsare at firstsolidandlatertheycanalize andbranchrepeatedlytoformthe duct
system.
The terminal partsof the duct systemdevelopintosecretoryacini.
As the salivaryglandsdevelopnearthe junctional areabetweenthe ectoderm of the stomatodaeum
and the endodermof the foregut,itisdifficulttodeterminewhethertheyare ectodermalor
endodermal.
major salivary glands
• PAROTID GLAND
(PARA-AROUND,OTIC-EAR)
LARGEST OF THE SALIVARYGLANDS.
WEIGHS ABOUT 15-28g.
IRREGULAR, LOBULATED, YELLOWISH MASS.
SHAPE- WEDGE SHAPED.
SITUATED BELOW THE EXTERNAL ACOUSTICMEATUS BETWEEN THE RAMUS OFTHE MANDIBLE
ANDSTERNOMASTOID.
3. THE ACCESSORYPAROTIDLIES BETWEEN THE ZYGOMATIC ARCH ANDTHE PAROTIDDUCT.
• Parotid capsule
INVESTING LAYER OF DEEP CERVICAL FASCIASPLITS BETWEEN THE
ANGLE OF MANDIBLE AND THE MASTOID PROCESS TO FORM TWO
LAMINAS WHICHENCLOSES THE GLAND.
SUPERFICIAL LAMINA.
DEEP LAMINA.
A PORTION OF DEEP LAMINA EXTENDING BETWEEN THE STYLOID
PROCESS AND THE MANDIBLE THICKENS TO FORM
STYLOMANDIBULAR LIGAMENT WHICHSEPERATES THE PAROTID
FROM THE SUBMANDIBULAR SALIVARY GLAND.
• RELATIONS OF PAROTID GLAND
PAROTID GLANDHAS FOUR SURFACES:
a) SUPERIORSURFACE.
b) SUPERFICIALSURFACE.
c) ANTEROMEDIALSURFACE.
d) POSTEROMEDIALSURFACE.
APEX:
CERVICALBRANCHOFFACIALNERVE ANDTWO DIVISIONSOFRETROMANDIBULARVEIN EMERGE
THROUGH IT.
SUPERIOR SURFACE:
CARTILAGENOUSPARTOF EXTERNALACOUSTIC MEATUS.
POSTERIORSURFACEOF TMJ
SUPERFICIALTEMPORAL VESSELS
AURICULOTEMPORALNERVE.
SUPERFICIALSURFACE:
4. LARGEST OF THE FOURSURFACES.
COVERED BY:
A) SKIN
B) SUPERFICIALFASCIA CONTAININGANTERIORBRANCHESOFGREATER
AURICULAR NERVE.
C) PAROTIDFASCIA.
D) A FEW DEEP PAROTIDLYMPH NODES.
ANTEROMEDIAL SURFACE:
A) MASSETER.
B) LATERAL SURFACEOF TMJ.
C) POSTERIOR BORDER OFRAMUS OF MANDIBLE.
D) MEDIAL PTERYGOID.
E) EMERGING BRANCHESOF FACIALNERVE.
POSTEROMEDIAL SURFACE:
MASTOIDPROCESS,STERNOMASTOID,POSTERIORBELLYOF DIGASTRIC.
STYLOID PROCESS.
EXTERNALCAROTIDARTERY ENTERS THE
GLANDTHROUGH THIS SURFACE.
FROM MEDIAL TO LATERAL SIDE , THESE ARE:
ARTERIES:
THE EXTERNALCAROTID ARTERY.
MAXILLARY ARTERY
SUPERFICIALTEMPORAL VESSELS.
POSTERIORAURICULAR ARTERY.
5. VEINS:
THE RETROMANDIBULAR ISFORMED WITHIN THE GLAND BY THE UNION OF
SUPERFICIALTEMPORAL AND MAXILLARY VEINS.
IN THE LOWER PARTOF THE GLAND,THE VEIN DIVIDESINTOANTERIORAND
POSTERIORDIVISIONSWHICHEMERGE AT THE APEX OFTHE GLAND.
NERVE:
FACIALNERVEENTERS THE GLAND THROUGH ITS POSTEROMEDIAL
SURFACE.
THE TERMINAL BRANCHESLEAVE THE GLAND THROUGH ITS
ANTEROMEDIALSURFACE.
• Parotid duct
(stensonsduct)
Thick walled.
5 cm long.
Emergesfrom the middle ofthe anterior border ofthe gland.
runs forwards and downwards on the MASSETER.
The duct opensinto the vestibule ofthe mouth
opposite the crown of the second molar tooth.
• Relationsof parotid duct
The parotidduct can be feltonthe face androlledonthe anteriorborderof the masseterbypressing
the fingerbackwardsonit ( withteethclenchedtomake the muscle tense).
• The parotidglandssecrete entirelythe seroustype of salivarysecretion.About90% of the total
salivaryflowisfromthe parotidgland.
• Restingflowof salivafromthisglandis0.4 ml/minandon stimulationis1.0-2.0ml/min.
BLOOD SUPPLY:
6. Parotid gland is suppliedbyEXTERNAL CAROTID ARTERY.(transverse facial
and maxillary)
Veinsdrain into EXTERNAL JUGULARVEIN.
LYMPHATIC DRAINAGE:
Lymph drains SUPERFICIALand to the UPPER DEEP
CERVICAL NODES FROM PREAURICULARGROUP.
• NERVE SUPPLY
SYMPATHETIC NERVES:
Are vasomotor and derivedfromplexusaround the EXTERNAL
CAROTID ARTERY.
PARASYMPATHETIC NERVES:
Are secretomotor.
PREGANGLIONICFIBERS :
INFERIOR SALIVATORY NUCLEUS
↓
GLOSSOPHARYNGEALNERVE
↓
TYMPANICBRANCH
↓
TYMPANICPLEXUS
↓
LESSER PETROSAL NERVE
↓
OTIC GANGLION
7. postganglionicfibersfrom
OTIC GANGLION
↓
AURICULOTEMPORAL NERVE
↓
PAROTID GLAND
SENSORY FIBERS:
To the gland: AURICULOTEMPORAL NERVE.
To parotid fascia: SENSORY FIBERS OF GREATER AURICULAR
NERVE
• SUBMANDIBULAR SALIVARYGLAND
Irregular, size of a walnut.
Situatedin anterior part of digastric triangle.
Dividedby posteriorborder of mylohyoid into a larger part superficial to the muscle and a
smallerpart lyingdeepto the muscle.
enclosedbetweentwolayers ofdeepcervical fascia.
a)superficial
b)deep
SUPERFICIALPART:
fillsthe digastric triangle.
reachesto the anterior belly
of digastric and back to the
stylomandibular ligament.
extendsupwards upto the
mylohyoidline.
8. 3 surfaces:
INFERIOR, LATERAL,
MEDIAL.
• Relationsof submandibulargland
a)INFERIOR SURFACE
a)skin.
b)platysma.
c)cervical branchof the facial nerve.
d)deepfascia.
e)facial vein.
f)submandibularlymphnodes.
b)LATERAL SURFACE
a)submandibularfossaonthe mandible.
b)insertionof the medial pterygoid.
c)facial artery.
c)MEDIAL SURFACE
a)anteriorpart:mylohyoidmuscle,nerve andvessels.
b)middlepart: hyoglossus,styloglossus,the lingual nerve,the submandibularganglionand
the hypoglossal nerve.
c)posteriorpart:the styloglossus,the stylohyoidligament,the ninthnerve,andthe wall of
the pharynx.Inferiorlyitoverlapsthe stylohyoidandthe postereriorbellyOf the digastric.
•
SUBMANDIBULAR DUCT
Thin walled.
About 5 cm long.
Emergesat the anteriorend of deeppart of the gland.
9. Runs forward on the hyoglossusbetween lingual and the hypoglossal nerve.
Openson the floor ofthe mouth, on the summitof the sublingual papilla,
at the side of the frenulumofthe
tongue.
BLOOD SUPPLY:
SuppliedbyFACIALARTERY.
VeinsdrainintoCOMMON FACIALand LINGUAL VEIN.
LYMPHATIC DRAINAGE:
TO SUBMANDIBULAR LYMPH NODES.
NERVE SUPPLY:
SENSORY- fromlingual nerve.
SYMPATHETIC- from the plexusonFACIALARTERY.
PARASYMPATHETIC- preganglionicfibersfrom
SuperiorSalivatoryNucleus
↓
sensoryrootof the facial nerve
↓
↓
the Geniculate ganglion
↓
Facial Nerve
↓
ChordaTympani
↓
10. Lingual Nerve
↓
SUBMANDIBULAR GANGLION
↓
postganglionicfiberstothe gland
• APPLIED ANATOMY
• MOST COMMONTO BE AFFECTED BY CALCULUS.
• INCISIONTO BE PLACED AN INCH BELOW THE ANGLETO
PRESERVE MANDIBULAR BRANCH OF FACIAL NERVE.
•
SUBLINGUALSALIVARY GLAND
Smallestof the three salivary glands.
Almondshaped.
Weighs3-4 gm.
Liesabove the mylohyoid,belowthe mucosa of the floorof the mouth, medial to the
sublingual fossaof the mandible and lateral to the genioglossus.
DUCTS:
most of the ducts opendirectly intothe floor ofthe mouth on the summitof the sublingual fold.A
fewof them joinssubmandibularduct.
• SECRETION OF SALIVA
• The dailysecretionof salivanormallyrangesbetweenabout800-1500ml. Salivacontainstwo
majortypesof proteinsecretion:
a) seroussecretion:that containsPTYALIN (anα-amylase),whichisanenzyme fordigesting
starches.
b) mucous secretion:thatcontainsmucinfor lubricatingandforsurface protective purposes.
• Nervousregulationof salivary secretion:
• Salivaiscontinuouslysecretedinthe mouth.
11. • Salivaryglandsare controlledmainlybyparasympatheticnervoussignalsfromthe superiorand
the inferiorsalivatory nuclei inthe brainstem.
• Salivationcanalsobe stimulatedorinhibitedbynervoussignalsarrivinginthe salivatorynuclei
fromhighercentersof the CNS,e.g.,whena personsmellsoreatsfavorite foods
• Sympatheticstimulationcan alsoincrease salivationamoderate amountbutmuchlesssothan
doesparasympatheticstimulation.The sympatheticnervesoriginate fromsuperiorcervical
gangliaandthentravel alongbloodvesselstothe salivaryglands.
• STRUCTURE OF THE SALIVARY GLAND
A SALIVARY GLAND CONSISTSOF
SERIES OF BRANCHED DUCTS
TERMINATING IN
SECRETORY END PIECES OR ACINI.
THE MAIN EXCRETORY DUCT DIVIDES
INTO SMALLER INTERLOBULAR AND
INTRALOBULAR EXCRETORY DUCTS
THAT ENTER THE LOBES
AND LOBULES OF THE GLAND.
THE PREDOMINANT INTRALOBULAR DUCTAL COMPONENTIS THE STRIATED DUCT.
INTERCALATED DUCT JOINS SECRETORY DUCT TO THE SECRETORY END PIECES.
STRIATED DUCT PLAYS A MAJOR ROLE IN THE
MODIFICATIONOF SALIVA PRODUCED BY THE
SECRETORY END PIECES.
• SECRETORY CELLS
• TWO MAINTYPES OF SECRETORY CELLS ARE PRESENT:
i) SEROUS CELLS.
II) MUCOUSCELLS.
12. • SEROUS CELLS
• Secretoryendpiecesthatare composedof serouscellsare typicallyspherical andconsistof 8 to
12 cellssurroundingacentral lumen.
1) Structure:
• The cellsare pyramidal,withabroadbase adjacentto the connective tissuestromaanda
narrow apex formingpartof the lumenof the endpiece.
• Numeroussecretorygranules,inwhichmacromolecularcomponentsof the salivaare stored,
are presentinthe apical cytoplasm
2) Function:
• These cellswhichsecrete awateryfluid,essentiallydevoidof mucusandproduce proteinsand
glycoproteinswhichhave welldefinedenzymatic,antimicrobial andcalciumbindingactivities.
• These proteinsare modifiedbythe additionof sugarresidues(glycosylation) andthusare called
glycoproteins.Typicallyserousglycoproteinshave N-linkedoligosaccharide sidechains.
• Structure of serouscells
• MUCOUSCELLS
• Secretoryend piecesthatare composedof mucouscellstypicallyhave atubularconfiguration;
whencut incross section,these tubulesappearasroundprofileswithmucouscellssurrounding
a central lumenof largersize thanthat of serousendpieces.
1) Structure:
• The most prominentfeature of mucouscellsisthe accumulationinthe apical cytoplasmof large
amountsof secretoryproduct(mucus),whichcompressesthe nucleusandendoplasmic
reticulumagainstthe basal cell membrane.
2) Function:
• These cellsproduce mucinswhichhave aproteincore (apomucins).
• Mucins functionmainlytolubricate andformsabarrieron surfacesandto bindand aggregate
microorganisms.
• Structure of mucouscells
Myoepithelial cells
• These are contractile cellsassociatedwiththe secretory endpiecesandintercalatedductsof the
salivaryglands.
13. • Theyare locatedbetweenthe basal laminaandthe secretoryorduct cellsandare joinedtothe
cellsbydesmosomes.
1) Structure:
• Myoepithelial cellspresentaroundthe secretoryendpieceshave a stellate shape;numerous
branchingprocessesextendfromthe cell bodytosurroundandembrace the endpiece.
2) Function:
• Contractionof the myoepithelialcellsisthoughttoprovide supportforthe endpiecesduring
active secretionof saliva.
• The cells mayhelpto expel the primarysalivafromthe endpiece intothe ductsystem.
• Contractionof the myoepithelialcellsof the intercalatedductsmayshortenandwidenthe
ducts,helpingtomaintaintheirpatency.
• DUCTS
3 CLASSES OF DUCTS:
INTERCALATED DUCTS.
STRIATED DUCTS.
EXCRETORY DUCTS.
Intercalatedducts
• The overall diameterof the intercalatedductsissmallerthanthatof the endpieces,andtheir
luminaare larger.
• A few small secretorygranulesmaybe foundinapical cytoplasm, especiallyincellslocatednear
the endpieces.
2) Function:
• The intercalatedductscontribute macromolecularcomponents whichare storedintheir
secretorygranulestothe saliva.These include lactoferrinandlysozyme aportionof the fluid
componentof the primarysalivalikelyisaddedinthe intercalatedductregion.
• Undifferentiatedcellsbelievedtobe presentinthe intercalatedductsalsomayproliferate and
undergodifferentiationtoreplace damagedordyingcellsinthe endpiecesandstriatedducts.
Striated ducts
14. • The striatedducts,whichreceive the primarysalivafromthe intercalatedducts,constitutethe
largestportionof the duct system.
1) Structure:
• Striatedductcellsare columnar,witha centrallyplacednucleusandapale,acidophilic
cytoplasm.
2) Function:
• An importantfunctionof striatedductcellsismodificationof the primarysalivabyreabsorption
and secretionof electrolytes.
• The granulescontainkallilrein,andothersecretoryproteins.
• The presence of vesiclessuggeststhatthe cellsmayparticipate inendocytosisof the substances
fromthe lumen.
Excretory ducts
• The excretoryductsare locatedinthe connective tissue septabetweenthe lobulesof the gland
that is,inan extralobularorinterlobularlocation.
1) Structure:
• Theyare largerindiameterthanstriatedductsand have a pseudostratifiedepithelium
2) Function:
• It ismainduct throughwhichsalivaissecretedinthe oral cavity.
SALIVA
DEFINITION
• A clearliquidsecreted intothe mouthbythe salivary glandsandmucous glands of the mouth;it
moistens the mouthandstartsthe digestion of starches.(WEBSTER’SDICTIONARY)
• Wateryfilm/liquidproducedbyglandsinthe mouthcomprisingof organicandinorganic
constituentswhichhelpsinchewing,swallowingand digestion.
AMOUNTOF DAILY SALIVASECRETION:
• The dailysecretionof salivarangesnormallybetween500 and 1500 milliliters.
• Normal stimulatedsecretionrate inadultsis1 – 2 ml per minute.Itmaybe reducedtolessthan
0.1ml permin insevere salivaryglandmalfunction(xerostomia/drymouth).
Circadianvariation:
15. • Unstimulatedflow peaksatapprox 5 pm in mostindividuals,withaminimumflow atnight
(0.05ml/min) duringsleepallowingpopulationsof bacteriatobuildupinmouth - resultis a
dragon breathinmorning.
PROPERTIES
• Salivaisa merocrine secretion. Inman,the salivaisamore or lessturbidandslightly viscidfluid
and generally of analkaline reaction.
• The abilitytodraw out a threadof salivaisknownas ‘Spinnbarkelt’.
ph of saliva:Salivahasa pH between6.0and 7.4 (withthe higherpHexhibiteduponincreased
secretion).
FORMATION OF SALIVA
• Salivaisformedintwostages
1) Primary secretionisformedactivelybymovementof sodium&chloride ionsintolumenof the acini,
creatingan osmoticgradient,whichleadstopassive movementof water.This‘primaryisotonicsaliva’
has plasmalike concentrationof Na,Cl & HCO3
2) Secondary secretion- the primarysalivaismodifiedasitflowsdownthe ductsystem.Sodiumions
are activelyreabsorbed&potassiumandbicarbonate ionsare secreted.
CONTROL OF SALIVATION
Salivaryglandsare unusual amongthe glandsof the digestive tractinbeingpurelyundercontrol of the
autonomicnervoussystem, whichcontrolsboththe volume andtype of salivasecreted.
• Stimulationof Para-sympatheticfibersof 7th
and9th
nerve produce anincrease involume of
saliva,makingitthinandwatery
• Stimulationof the sympatheticfibersresultinsecretionsmallinamountcontaininghigh
concentrationof mucinandptyalin
COMPOSITIONOF SALIVA
• - 99% WATER
• - 1% SOLIDS
* ORGANIC60%
* INORGANIC40%
